public inbox for linuxppc-dev@ozlabs.org 
 help / color / mirror / Atom feed

• * Re: [PATCH v2 2/4] usb: dwc2: Add binding for AHB burst
         [not found]   ` <e01e1b30-a399-94cc-33c9-625008b31d4b@synopsys.com>
  @ 2016-11-21 21:10     ` Christian Lamparter
    2016-11-22  3:32       ` John Youn
    0 siblings, 1 reply; 5+ messages in thread
  From: Christian Lamparter @ 2016-11-21 21:10 UTC (permalink / raw)
    To: John Youn
    Cc: Christian Lamparter, Rob Herring, Stefan Wahren, Felipe Balbi,
  	linux-usb@vger•kernel.org, devicetree@vger•kernel.org,
  	Mark Rutland, linuxppc-dev, Michael Ellerman, Paul Mackerras,
  	Benjamin Herrenschmidt
  
  Hello John,
  
  On Monday, November 21, 2016 12:16:31 PM CET John Youn wrote:
  > On 11/18/2016 12:18 PM, Christian Lamparter wrote:
  > > On Friday, November 18, 2016 8:16:08 AM CET Rob Herring wrote:
  > >> On Thu, Nov 17, 2016 at 04:35:10PM +0100, Stefan Wahren wrote:
  > >>> Hi John,
  > >>>
  > >>> Am 17.11.2016 um 00:47 schrieb John Youn:
  > >>>> Add the "snps,ahb-burst" binding and read it in.
  > >>>>
  > >>>> This property controls which burst type to perform on the AHB bus as a
  > >>>> master in internal DMA mode. This overrides the legacy param value,
  > >>>> which we need to keep around for now since several platforms use it.
  > >>>>
  > >>>> Some platforms may see better or worse performance based on this
  > >>>> value. The HAPS platform is one example where all INCRx have worse
  > >>>> performance than INCR.
  > >>>>
  > >>>> Other platforms (such as the Canyonlands board) report that the default
  > >>>> value causes system hangs.
  > >>>>
  > >>>> Signed-off-by: John Youn <johnyoun@synopsys•com>
  > >>>> Cc: Christian Lamparter <chunkeey@googlemail•com>
  > >>>> ---
  > >>>>  Documentation/devicetree/bindings/usb/dwc2.txt |  2 +
  > >>>>  drivers/usb/dwc2/core.h                        |  9 +++++
  > >>>>  drivers/usb/dwc2/params.c                      | 56 ++++++++++++++++++++++++++
  > >>>>  3 files changed, 67 insertions(+)
  > >>>>
  > >>>> diff --git a/Documentation/devicetree/bindings/usb/dwc2.txt b/Documentation/devicetree/bindings/usb/dwc2.txt
  > >>>> index 6c7c2bce..9e7b4b4 100644
  > >>>> --- a/Documentation/devicetree/bindings/usb/dwc2.txt
  > >>>> +++ b/Documentation/devicetree/bindings/usb/dwc2.txt
  > >>>
  > >>> according to Documentation/devicetree/bindings/submitting-patches.txt
  > >>> this change should be a separate patch.
  > >>>
  > >>>> @@ -26,6 +26,8 @@ Optional properties:
  > >>>>  Refer to phy/phy-bindings.txt for generic phy consumer properties
  > >>>>  - dr_mode: shall be one of "host", "peripheral" and "otg"
  > >>>>    Refer to usb/generic.txt
  > >>>> +- snps,ahb-burst: specifies the ahb burst length. Valid arguments are:
  > >>>> +  "SINGLE", "INCR", "INCR4", "INCR8", "INCR16". Defaults to "INCR4".
  > >>>
  > >>> This doesn't apply in case of the bcm2835. I would prefer this option is
  > >>> ignored in that case with a dev_warn("snps,ahb-burst is not supported on
  > >>> this platform").
  > >>
  > >> Also, perhaps you should allow that the compatible string can define the 
  > >> default.
  > >>
  > > I hoped you would say that :).
  > > 
  > > I've attached a patch (on top of John Youn changes) that does
  > > just that for the amcc,dwc-otg. I put the GAHBCFG_HBSTLEN_INCR
  > > value into the .data, if that's a problem, I can certainly 
  > > respin the patch and put it in a dedicated struct.
  > > 
  > > Regards
  > > 
  > > Christian
  > > ---
  > > From 4c31a029dde714828810b1c3e61a5b1412ac939a Mon Sep 17 00:00:00 2001
  > > From: Christian Lamparter <chunkeey@gmail•com>
  > > Date: Fri, 18 Nov 2016 21:03:19 +0100
  > > Subject: [PATCH] usb: dwc2: add a default ahb-burst setting for amcc,dwc-otg
  > > 
  > > This patch adds a of_device_id table which can be used by
  > > existing devices to supply a ahb-burst value for the platform
  > > without having to add a "snps,ahb-burst" entry to the dts.
  > > 
  > > Note: Adding new devices to this table is discouraged.
  > >       please consider adding the "snps,ahb-burst" property
  > >       with the correct configuration to your device tree
  > >       file instead.
  > > 
  > > Signed-off-by: Christian Lamparter <chunkeey@gmail•com>
  > > ---
  > >  drivers/usb/dwc2/params.c | 22 ++++++++++++++++++++++
  > >  1 file changed, 22 insertions(+)
  > > 
  > > diff --git a/drivers/usb/dwc2/params.c b/drivers/usb/dwc2/params.c
  > > index e0fc9aa..51be266 100644
  > > --- a/drivers/usb/dwc2/params.c
  > > +++ b/drivers/usb/dwc2/params.c
  > > @@ -1097,6 +1097,22 @@ static const char *const ahb_bursts[] = {
  > >  	[GAHBCFG_HBSTLEN_INCR16]	= "INCR16",
  > >  };
  > >  
  > > +/*
  > > + * This table provides AHB burst configuration for existing
  > > + * device tree bindings that work poorly with the default setting.
  > > + *
  > > + * Note: Adding new devices to this table is discouraged.
  > > + *	 please consider adding the "snps,ahb-burst" property
  > > + *	 with the correct configuration to your device tree
  > > + *	 file instead.
  > > + */
  > > +static const struct of_device_id dwc2_compat_ahb_bursts[] = {
  > > +	{
  > > +		.compatible = "amcc,dwc-otg",
  > > +		.data = (void *) GAHBCFG_HBSTLEN_INCR16,
  > > +	},
  > > +};
  > > +
  > >  static int dwc2_get_property_ahb_burst(struct dwc2_hsotg *hsotg)
  > >  {
  > >  	struct device_node *node = hsotg->dev->of_node;
  > > @@ -1107,6 +1123,12 @@ static int dwc2_get_property_ahb_burst(struct dwc2_hsotg *hsotg)
  > >  	ret = device_property_read_string(hsotg->dev,
  > >  					  "snps,ahb-burst", &str);
  > >  	if (ret < 0) {
  > > +		const struct of_device_id *match;
  > > +
  > > +		match = of_match_node(dwc2_compat_ahb_bursts, node);
  > > +		if (match)
  > > +			ret = (int)match->data;
  > > +
  > >  		return ret;
  > >  	} else if (of_device_is_compatible(node, "brcm,bcm2835-usb")) {
  > >  		dev_warn(hsotg->dev,
  > > 
  > I'd prefer if you use the binding which requires no extra code in
  > dwc2.
  I'm fine with either option. However it think that this would require
  that either Mark or Rob would allow an exception to the "keep existing
  dts the way they are) and ack the following change to the canyonlands.dts. 
  
  In that case I wouldn't need the overwrite in dwc2_get_property_ahb_burst.
  
  Regards,
  Christian
  ---
  >From e78604cb0b8ea8db277ef9bf321a613f8e0c7129 Mon Sep 17 00:00:00 2001
  From: Christian Lamparter <chunkeey@gmail•com>
  Date: Mon, 21 Nov 2016 21:46:19 +0100
  Subject: [PATCH] powerpc/dts: set snps,ahb-burst to INCR16
  
  The dwc2 driver defaults to INCR4 which can cause a
  system hang when the USB and SATA is used concurrently.
  
  Note: This patch requires:
  	"usb: dwc2: add amcc,dwc-otg support"
  	(which already landed in the usb subsystem queue)
  	and "usb: dwc2: Add AHB burst configuration"
  
  Signed-off-by: Christian Lamparter <chunkeey@gmail•com>
  ---
   arch/powerpc/boot/dts/canyonlands.dts | 1 +
   1 file changed, 1 insertion(+)
  
  diff --git a/arch/powerpc/boot/dts/canyonlands.dts b/arch/powerpc/boot/dts/canyonlands.dts
  index 0d6ac92..90db712 100644
  --- a/arch/powerpc/boot/dts/canyonlands.dts
  +++ b/arch/powerpc/boot/dts/canyonlands.dts
  @@ -179,6 +179,7 @@
   
   		USBOTG0: usbotg@bff80000 {
   			compatible = "amcc,dwc-otg";
  +			snps,ahb-burst = "INCR16";
   			reg = <0x4 0xbff80000 0x10000>;
   			interrupt-parent = <&USBOTG0>;
   			#interrupt-cells = <1>;
  -- 
  2.10.2
  
  ^ permalink raw reply related	[flat|nested] 5+ messages in thread

• • * Re: [PATCH v2 2/4] usb: dwc2: Add binding for AHB burst
      2016-11-21 21:10     ` [PATCH v2 2/4] usb: dwc2: Add binding for AHB burst Christian Lamparter
    @ 2016-11-22  3:32       ` John Youn
      2016-11-22 20:51         ` Christian Lamparter
      0 siblings, 1 reply; 5+ messages in thread
    From: John Youn @ 2016-11-22  3:32 UTC (permalink / raw)
      To: Christian Lamparter, John Youn
      Cc: Rob Herring, Stefan Wahren, Felipe Balbi,
    	linux-usb@vger•kernel.org, devicetree@vger•kernel.org,
    	Mark Rutland, linuxppc-dev@lists•ozlabs.org, Michael Ellerman,
    	Paul Mackerras, Benjamin Herrenschmidt
    
    On 11/21/2016 1:10 PM, Christian Lamparter wrote:
    > Hello John,
    > 
    > On Monday, November 21, 2016 12:16:31 PM CET John Youn wrote:
    >> On 11/18/2016 12:18 PM, Christian Lamparter wrote:
    >>> On Friday, November 18, 2016 8:16:08 AM CET Rob Herring wrote:
    >>>> On Thu, Nov 17, 2016 at 04:35:10PM +0100, Stefan Wahren wrote:
    >>>>> Hi John,
    >>>>>
    >>>>> Am 17.11.2016 um 00:47 schrieb John Youn:
    >>>>>> Add the "snps,ahb-burst" binding and read it in.
    >>>>>>
    >>>>>> This property controls which burst type to perform on the AHB bus as a
    >>>>>> master in internal DMA mode. This overrides the legacy param value,
    >>>>>> which we need to keep around for now since several platforms use it.
    >>>>>>
    >>>>>> Some platforms may see better or worse performance based on this
    >>>>>> value. The HAPS platform is one example where all INCRx have worse
    >>>>>> performance than INCR.
    >>>>>>
    >>>>>> Other platforms (such as the Canyonlands board) report that the default
    >>>>>> value causes system hangs.
    >>>>>>
    >>>>>> Signed-off-by: John Youn <johnyoun@synopsys•com>
    >>>>>> Cc: Christian Lamparter <chunkeey@googlemail•com>
    >>>>>> ---
    >>>>>>  Documentation/devicetree/bindings/usb/dwc2.txt |  2 +
    >>>>>>  drivers/usb/dwc2/core.h                        |  9 +++++
    >>>>>>  drivers/usb/dwc2/params.c                      | 56 ++++++++++++++++++++++++++
    >>>>>>  3 files changed, 67 insertions(+)
    >>>>>>
    >>>>>> diff --git a/Documentation/devicetree/bindings/usb/dwc2.txt b/Documentation/devicetree/bindings/usb/dwc2.txt
    >>>>>> index 6c7c2bce..9e7b4b4 100644
    >>>>>> --- a/Documentation/devicetree/bindings/usb/dwc2.txt
    >>>>>> +++ b/Documentation/devicetree/bindings/usb/dwc2.txt
    >>>>>
    >>>>> according to Documentation/devicetree/bindings/submitting-patches.txt
    >>>>> this change should be a separate patch.
    >>>>>
    >>>>>> @@ -26,6 +26,8 @@ Optional properties:
    >>>>>>  Refer to phy/phy-bindings.txt for generic phy consumer properties
    >>>>>>  - dr_mode: shall be one of "host", "peripheral" and "otg"
    >>>>>>    Refer to usb/generic.txt
    >>>>>> +- snps,ahb-burst: specifies the ahb burst length. Valid arguments are:
    >>>>>> +  "SINGLE", "INCR", "INCR4", "INCR8", "INCR16". Defaults to "INCR4".
    >>>>>
    >>>>> This doesn't apply in case of the bcm2835. I would prefer this option is
    >>>>> ignored in that case with a dev_warn("snps,ahb-burst is not supported on
    >>>>> this platform").
    >>>>
    >>>> Also, perhaps you should allow that the compatible string can define the 
    >>>> default.
    >>>>
    >>> I hoped you would say that :).
    >>>
    >>> I've attached a patch (on top of John Youn changes) that does
    >>> just that for the amcc,dwc-otg. I put the GAHBCFG_HBSTLEN_INCR
    >>> value into the .data, if that's a problem, I can certainly 
    >>> respin the patch and put it in a dedicated struct.
    >>>
    >>> Regards
    >>>
    >>> Christian
    >>> ---
    >>> From 4c31a029dde714828810b1c3e61a5b1412ac939a Mon Sep 17 00:00:00 2001
    >>> From: Christian Lamparter <chunkeey@gmail•com>
    >>> Date: Fri, 18 Nov 2016 21:03:19 +0100
    >>> Subject: [PATCH] usb: dwc2: add a default ahb-burst setting for amcc,dwc-otg
    >>>
    >>> This patch adds a of_device_id table which can be used by
    >>> existing devices to supply a ahb-burst value for the platform
    >>> without having to add a "snps,ahb-burst" entry to the dts.
    >>>
    >>> Note: Adding new devices to this table is discouraged.
    >>>       please consider adding the "snps,ahb-burst" property
    >>>       with the correct configuration to your device tree
    >>>       file instead.
    >>>
    >>> Signed-off-by: Christian Lamparter <chunkeey@gmail•com>
    >>> ---
    >>>  drivers/usb/dwc2/params.c | 22 ++++++++++++++++++++++
    >>>  1 file changed, 22 insertions(+)
    >>>
    >>> diff --git a/drivers/usb/dwc2/params.c b/drivers/usb/dwc2/params.c
    >>> index e0fc9aa..51be266 100644
    >>> --- a/drivers/usb/dwc2/params.c
    >>> +++ b/drivers/usb/dwc2/params.c
    >>> @@ -1097,6 +1097,22 @@ static const char *const ahb_bursts[] = {
    >>>  	[GAHBCFG_HBSTLEN_INCR16]	= "INCR16",
    >>>  };
    >>>  
    >>> +/*
    >>> + * This table provides AHB burst configuration for existing
    >>> + * device tree bindings that work poorly with the default setting.
    >>> + *
    >>> + * Note: Adding new devices to this table is discouraged.
    >>> + *	 please consider adding the "snps,ahb-burst" property
    >>> + *	 with the correct configuration to your device tree
    >>> + *	 file instead.
    >>> + */
    >>> +static const struct of_device_id dwc2_compat_ahb_bursts[] = {
    >>> +	{
    >>> +		.compatible = "amcc,dwc-otg",
    >>> +		.data = (void *) GAHBCFG_HBSTLEN_INCR16,
    >>> +	},
    >>> +};
    >>> +
    >>>  static int dwc2_get_property_ahb_burst(struct dwc2_hsotg *hsotg)
    >>>  {
    >>>  	struct device_node *node = hsotg->dev->of_node;
    >>> @@ -1107,6 +1123,12 @@ static int dwc2_get_property_ahb_burst(struct dwc2_hsotg *hsotg)
    >>>  	ret = device_property_read_string(hsotg->dev,
    >>>  					  "snps,ahb-burst", &str);
    >>>  	if (ret < 0) {
    >>> +		const struct of_device_id *match;
    >>> +
    >>> +		match = of_match_node(dwc2_compat_ahb_bursts, node);
    >>> +		if (match)
    >>> +			ret = (int)match->data;
    >>> +
    >>>  		return ret;
    >>>  	} else if (of_device_is_compatible(node, "brcm,bcm2835-usb")) {
    >>>  		dev_warn(hsotg->dev,
    >>>
    >> I'd prefer if you use the binding which requires no extra code in
    >> dwc2.
    > I'm fine with either option. However it think that this would require
    > that either Mark or Rob would allow an exception to the "keep existing
    > dts the way they are) and ack the following change to the canyonlands.dts. 
    
    I don't know about that. Under what circumstance can the dts change?
    
    The canyonlands dts was binding to an external vendor driver. So it
    wasn't documented nor expected to work with dwc2 until your recent
    patch adding the compatible string.
    
    Systems that use the vendor driver will still work with the dts. If
    you remove the vendor driver and configure it to use dwc2, it won't
    work due to a quirk of the canyonlands hardware, for which you need to
    add a dts property.
    
    I think this is reasonable. Rob or Mark, any feedback?
    
    One of the reasons I don't want to add the code in dwc2 is because I'm
    trying to make dwc2 a generic IP driver like dwc3.
    
    Regards,
    John
    
    > 
    > In that case I wouldn't need the overwrite in dwc2_get_property_ahb_burst.
    > 
    > Regards,
    > Christian
    > ---
    > From e78604cb0b8ea8db277ef9bf321a613f8e0c7129 Mon Sep 17 00:00:00 2001
    > From: Christian Lamparter <chunkeey@gmail•com>
    > Date: Mon, 21 Nov 2016 21:46:19 +0100
    > Subject: [PATCH] powerpc/dts: set snps,ahb-burst to INCR16
    > 
    > The dwc2 driver defaults to INCR4 which can cause a
    > system hang when the USB and SATA is used concurrently.
    > 
    > Note: This patch requires:
    > 	"usb: dwc2: add amcc,dwc-otg support"
    > 	(which already landed in the usb subsystem queue)
    > 	and "usb: dwc2: Add AHB burst configuration"
    > 
    > Signed-off-by: Christian Lamparter <chunkeey@gmail•com>
    > ---
    >  arch/powerpc/boot/dts/canyonlands.dts | 1 +
    >  1 file changed, 1 insertion(+)
    > 
    > diff --git a/arch/powerpc/boot/dts/canyonlands.dts b/arch/powerpc/boot/dts/canyonlands.dts
    > index 0d6ac92..90db712 100644
    > --- a/arch/powerpc/boot/dts/canyonlands.dts
    > +++ b/arch/powerpc/boot/dts/canyonlands.dts
    > @@ -179,6 +179,7 @@
    >  
    >  		USBOTG0: usbotg@bff80000 {
    >  			compatible = "amcc,dwc-otg";
    > +			snps,ahb-burst = "INCR16";
    >  			reg = <0x4 0xbff80000 0x10000>;
    >  			interrupt-parent = <&USBOTG0>;
    >  			#interrupt-cells = <1>;
    > 
    
    ^ permalink raw reply	[flat|nested] 5+ messages in thread

  • • * Re: [PATCH v2 2/4] usb: dwc2: Add binding for AHB burst
        2016-11-22  3:32       ` John Youn
      @ 2016-11-22 20:51         ` Christian Lamparter
        2016-11-22 21:46           ` Rob Herring
        2016-11-29  3:32           ` John Youn
        0 siblings, 2 replies; 5+ messages in thread
      From: Christian Lamparter @ 2016-11-22 20:51 UTC (permalink / raw)
        To: John Youn
        Cc: Christian Lamparter, Rob Herring, Stefan Wahren, Felipe Balbi,
      	linux-usb@vger•kernel.org, devicetree@vger•kernel.org,
      	Mark Rutland, linuxppc-dev@lists•ozlabs.org, Michael Ellerman,
      	Paul Mackerras, Benjamin Herrenschmidt
      
      On Monday, November 21, 2016 7:32:30 PM CET John Youn wrote:
      > On 11/21/2016 1:10 PM, Christian Lamparter wrote:
      > > On Monday, November 21, 2016 12:16:31 PM CET John Youn wrote:
      > >> On 11/18/2016 12:18 PM, Christian Lamparter wrote:
      > >>> On Friday, November 18, 2016 8:16:08 AM CET Rob Herring wrote:
      > >>>> Also, perhaps you should allow that the compatible string can define the 
      > >>>> default.
      > >>>>
      > >>> I hoped you would say that :).
      > >>>
      > >>> I've attached a patch (on top of John Youn changes) [...]
      > >>> ---
      > >>> Subject: [PATCH] usb: dwc2: add a default ahb-burst setting for amcc,dwc-otg
      > >>> [...]
      > >>> @@ -1097,6 +1097,22 @@ static const char *const ahb_bursts[] = {
      > >>> +/* [...] */
      > >>> +static const struct of_device_id dwc2_compat_ahb_bursts[] = {
      > >>> +	{
      > >>> +		.compatible = "amcc,dwc-otg",
      > >>> +		.data = (void *) GAHBCFG_HBSTLEN_INCR16,
      > >>> +	},
      > >>> +};
      > [...]
      > > >>> @@ -1107,6 +1123,12 @@ static int dwc2_get_property_ahb_burst(struct dwc2_hsotg *hsotg)
      > >>>  	ret = device_property_read_string(hsotg->dev, "snps,ahb-burst", &str);
      > >>>  	if (ret < 0) {
      > >>> +		const struct of_device_id *match;
      > >>> +
      > >>> +		match = of_match_node(dwc2_compat_ahb_bursts, node);
      > >>> +		if (match)
      > >>> +			ret = (int)match->data;
      > >>> +
      > [...]
      > >> I'd prefer if you use the binding which requires no extra code in
      > >> dwc2.
      > > I'm fine with either option. However it think that this would require
      > > that either Mark or Rob would allow an exception to the "keep existing
      > > dts the way they are) and ack the following change to the canyonlands.dts. 
      > 
      > I don't know about that. Under what circumstance can the dts change?
      As far as I know, the justification for not changing the DTS is that a
      compiled DTB might be stored in an read-only ROM on a board. So it would
      be impossible to update it. Hence, the driver have work with the existing
      (and sometimes buggy or incomplete) information to stay compatible.
      
      (Note: Thankfully, the canyonlands dtb is stored in flash, it's possible
      to update it. But it is an extra step that's not done automatically
      with make install). 
      
      > The canyonlands dts was binding to an external vendor driver. So it
      > wasn't documented nor expected to work with dwc2 until your recent
      > patch adding the compatible string.
      
      Oh, no that's not what happend. Let me explain why there was no "external 
      vendor driver": AMCC/APM were planing to upstream their hole platform. And
      in fact, the devs tried very hard to include their driver back in 2011 [0].
      But this driver was denied inclusion back then due to:
      
      "[...]
      I would also like to point out that the same Synopsys USB controller
      is used in a number of other SoCs (especially ARM chips), and
      supported by other drivers, some of these even in mainline.
      
      See http://thread.gmane.org/gmane.linux.usb.general/61714/focus=62139
      for a related thread.
      
      Instead of trying to add a completely new driver to mainline (and one
      which has been repeatedly been rejected), I vote for focusing on the
      existing driver code that is already in mainline, and testing and
      improving this so we can use a single implementation of this driver
      code for all SoCs that use the same IP block." [1]
      
      Of course: The listed link goes the "USB Host driver for i.MX28" driver.
      And this is an ehci-hcd like driver... Which is as you are well aware not
      that similar to the dwc2 OTG. And as far as I can tell: AMCC abandoned
      the patch series right there. 
      
      Note: AMCC did however succeed in pushing your employer's Synopsys
      DesignWare SATA and DMA drivers to the kernel back then. And I'm happy
      to report that both drivers are still around and working fine for the 460EX 
      (sata_dwc_460ex.c[2] and the DW AHB DMA [3]). (The drivers also work for
      different platforms than the original PPC. I know that because I helped
      Andy Shevchenko with testing and pushing some fixes to it when he was
      adding support for the Intel Quark SoC, which uses the DWC SATA and DMA).
      
      So Please?
      > Systems that use the vendor driver will still work with the dts. If
      > you remove the vendor driver and configure it to use dwc2, it won't
      > work due to a quirk of the canyonlands hardware, for which you need to
      > add a dts property.
      Sadly, there is no up to date vendor driver. The canyonlands.dts binding
      is still in place and the hardware works fine. I'm interested in this
      platform since it is a cheap BigEndian system which is useful for usb
      driver development (carl9170 and rtl8192su)... and I would like to
      have out-of-the-box support.
      
      > I think this is reasonable. Rob or Mark, any feedback?
      I recall that Rob has already voiced his opinion about the ahb-burst setting: 
      "Also, perhaps you should allow that the compatible string can define the default."
      
      And based on that, I made the "add a default ahb-burst setting for amcc,dwc-otg"
      patch above. Of course, it would be nice to have any feedback too. But unless I
      hear otherwise, I'll continue with posting patches to the dwc2 driver :). 
      
      > One of the reasons I don't want to add the code in dwc2 is because I'm
      > trying to make dwc2 a generic IP driver like dwc3.
      I understand that. And let me say, that I also have a dwc3 in my IPQ4019. 
      And adding support for it was as simple as adding just one compatible
      binding in dwc-of-simple [4].
      
      Regards,
      Christian
      
      [0] <http://thread.gmane.org/gmane.linux.usb.general/53348/focus=53913>
      [1] <https://lists.ozlabs.org/pipermail/linuxppc-dev/2012-May/097850.html>
      [2] <http://lxr.free-electrons.com/source/drivers/ata/sata_dwc_460ex.c>
      [3] <http://lxr.free-electrons.com/source/drivers/dma/dw/core.c>
      [4] <https://github.com/chunkeey/LEDE-IPQ40XX/blob/staging/target/linux/ipq40xx/patches-4.8/830-usb-dwc3-register-qca-ipq4019-dwc3-in-dwc3-of-simple.patch>
      
      ^ permalink raw reply	[flat|nested] 5+ messages in thread

    • • * Re: [PATCH v2 2/4] usb: dwc2: Add binding for AHB burst
          2016-11-22 20:51         ` Christian Lamparter
        @ 2016-11-22 21:46           ` Rob Herring
          2016-11-29  3:32           ` John Youn
          1 sibling, 0 replies; 5+ messages in thread
        From: Rob Herring @ 2016-11-22 21:46 UTC (permalink / raw)
          To: Christian Lamparter
          Cc: John Youn, Stefan Wahren, Felipe Balbi, linux-usb@vger•kernel.org,
        	devicetree@vger•kernel.org, Mark Rutland,
        	linuxppc-dev@lists•ozlabs.org, Michael Ellerman, Paul Mackerras,
        	Benjamin Herrenschmidt
        
        On Tue, Nov 22, 2016 at 2:51 PM, Christian Lamparter
        <chunkeey@googlemail•com> wrote:
        > On Monday, November 21, 2016 7:32:30 PM CET John Youn wrote:
        >> On 11/21/2016 1:10 PM, Christian Lamparter wrote:
        >> > On Monday, November 21, 2016 12:16:31 PM CET John Youn wrote:
        >> >> On 11/18/2016 12:18 PM, Christian Lamparter wrote:
        >> >>> On Friday, November 18, 2016 8:16:08 AM CET Rob Herring wrote:
        >> >>>> Also, perhaps you should allow that the compatible string can define the
        >> >>>> default.
        >> >>>>
        >> >>> I hoped you would say that :).
        >> >>>
        >> >>> I've attached a patch (on top of John Youn changes) [...]
        >> >>> ---
        >> >>> Subject: [PATCH] usb: dwc2: add a default ahb-burst setting for amcc,dwc-otg
        >> >>> [...]
        >> >>> @@ -1097,6 +1097,22 @@ static const char *const ahb_bursts[] = {
        >> >>> +/* [...] */
        >> >>> +static const struct of_device_id dwc2_compat_ahb_bursts[] = {
        >> >>> + {
        >> >>> +         .compatible = "amcc,dwc-otg",
        >> >>> +         .data = (void *) GAHBCFG_HBSTLEN_INCR16,
        >> >>> + },
        >> >>> +};
        >> [...]
        >> > >>> @@ -1107,6 +1123,12 @@ static int dwc2_get_property_ahb_burst(struct dwc2_hsotg *hsotg)
        >> >>>   ret = device_property_read_string(hsotg->dev, "snps,ahb-burst", &str);
        >> >>>   if (ret < 0) {
        >> >>> +         const struct of_device_id *match;
        >> >>> +
        >> >>> +         match = of_match_node(dwc2_compat_ahb_bursts, node);
        >> >>> +         if (match)
        >> >>> +                 ret = (int)match->data;
        >> >>> +
        >> [...]
        >> >> I'd prefer if you use the binding which requires no extra code in
        >> >> dwc2.
        >> > I'm fine with either option. However it think that this would require
        >> > that either Mark or Rob would allow an exception to the "keep existing
        >> > dts the way they are) and ack the following change to the canyonlands.dts.
        >>
        >> I don't know about that. Under what circumstance can the dts change?
        > As far as I know, the justification for not changing the DTS is that a
        > compiled DTB might be stored in an read-only ROM on a board. So it would
        > be impossible to update it. Hence, the driver have work with the existing
        > (and sometimes buggy or incomplete) information to stay compatible.
        >
        > (Note: Thankfully, the canyonlands dtb is stored in flash, it's possible
        > to update it. But it is an extra step that's not done automatically
        > with make install).
        >
        >> The canyonlands dts was binding to an external vendor driver. So it
        >> wasn't documented nor expected to work with dwc2 until your recent
        >> patch adding the compatible string.
        >
        > Oh, no that's not what happend. Let me explain why there was no "external
        > vendor driver": AMCC/APM were planing to upstream their hole platform. And
        > in fact, the devs tried very hard to include their driver back in 2011 [0].
        > But this driver was denied inclusion back then due to:
        >
        > "[...]
        > I would also like to point out that the same Synopsys USB controller
        > is used in a number of other SoCs (especially ARM chips), and
        > supported by other drivers, some of these even in mainline.
        >
        > See http://thread.gmane.org/gmane.linux.usb.general/61714/focus=62139
        > for a related thread.
        >
        > Instead of trying to add a completely new driver to mainline (and one
        > which has been repeatedly been rejected), I vote for focusing on the
        > existing driver code that is already in mainline, and testing and
        > improving this so we can use a single implementation of this driver
        > code for all SoCs that use the same IP block." [1]
        >
        > Of course: The listed link goes the "USB Host driver for i.MX28" driver.
        > And this is an ehci-hcd like driver... Which is as you are well aware not
        > that similar to the dwc2 OTG. And as far as I can tell: AMCC abandoned
        > the patch series right there.
        >
        > Note: AMCC did however succeed in pushing your employer's Synopsys
        > DesignWare SATA and DMA drivers to the kernel back then. And I'm happy
        > to report that both drivers are still around and working fine for the 460EX
        > (sata_dwc_460ex.c[2] and the DW AHB DMA [3]). (The drivers also work for
        > different platforms than the original PPC. I know that because I helped
        > Andy Shevchenko with testing and pushing some fixes to it when he was
        > adding support for the Intel Quark SoC, which uses the DWC SATA and DMA).
        >
        > So Please?
        >> Systems that use the vendor driver will still work with the dts. If
        >> you remove the vendor driver and configure it to use dwc2, it won't
        >> work due to a quirk of the canyonlands hardware, for which you need to
        >> add a dts property.
        > Sadly, there is no up to date vendor driver. The canyonlands.dts binding
        > is still in place and the hardware works fine. I'm interested in this
        > platform since it is a cheap BigEndian system which is useful for usb
        > driver development (carl9170 and rtl8192su)... and I would like to
        > have out-of-the-box support.
        >
        >> I think this is reasonable. Rob or Mark, any feedback?
        > I recall that Rob has already voiced his opinion about the ahb-burst setting:
        > "Also, perhaps you should allow that the compatible string can define the default."
        >
        > And based on that, I made the "add a default ahb-burst setting for amcc,dwc-otg"
        > patch above. Of course, it would be nice to have any feedback too. But unless I
        > hear otherwise, I'll continue with posting patches to the dwc2 driver :).
        
        And this is the correct thing to do. Requiring a dtb update is not.
        
        Rob
        
        ^ permalink raw reply	[flat|nested] 5+ messages in thread

      • * Re: [PATCH v2 2/4] usb: dwc2: Add binding for AHB burst
          2016-11-22 20:51         ` Christian Lamparter
          2016-11-22 21:46           ` Rob Herring
        @ 2016-11-29  3:32           ` John Youn
          1 sibling, 0 replies; 5+ messages in thread
        From: John Youn @ 2016-11-29  3:32 UTC (permalink / raw)
          To: Christian Lamparter, John Youn
          Cc: Rob Herring, Stefan Wahren, Felipe Balbi,
        	linux-usb@vger•kernel.org, devicetree@vger•kernel.org,
        	Mark Rutland, linuxppc-dev@lists•ozlabs.org, Michael Ellerman,
        	Paul Mackerras, Benjamin Herrenschmidt
        
        On 11/22/2016 12:51 PM, Christian Lamparter wrote:
        > On Monday, November 21, 2016 7:32:30 PM CET John Youn wrote:
        >> On 11/21/2016 1:10 PM, Christian Lamparter wrote:
        >>> On Monday, November 21, 2016 12:16:31 PM CET John Youn wrote:
        >>>> On 11/18/2016 12:18 PM, Christian Lamparter wrote:
        >>>>> On Friday, November 18, 2016 8:16:08 AM CET Rob Herring wrote:
        >>>>>> Also, perhaps you should allow that the compatible string can define the 
        >>>>>> default.
        >>>>>>
        >>>>> I hoped you would say that :).
        >>>>>
        >>>>> I've attached a patch (on top of John Youn changes) [...]
        >>>>> ---
        >>>>> Subject: [PATCH] usb: dwc2: add a default ahb-burst setting for amcc,dwc-otg
        >>>>> [...]
        >>>>> @@ -1097,6 +1097,22 @@ static const char *const ahb_bursts[] = {
        >>>>> +/* [...] */
        >>>>> +static const struct of_device_id dwc2_compat_ahb_bursts[] = {
        >>>>> +	{
        >>>>> +		.compatible = "amcc,dwc-otg",
        >>>>> +		.data = (void *) GAHBCFG_HBSTLEN_INCR16,
        >>>>> +	},
        >>>>> +};
        >> [...]
        >>>>>> @@ -1107,6 +1123,12 @@ static int dwc2_get_property_ahb_burst(struct dwc2_hsotg *hsotg)
        >>>>>  	ret = device_property_read_string(hsotg->dev, "snps,ahb-burst", &str);
        >>>>>  	if (ret < 0) {
        >>>>> +		const struct of_device_id *match;
        >>>>> +
        >>>>> +		match = of_match_node(dwc2_compat_ahb_bursts, node);
        >>>>> +		if (match)
        >>>>> +			ret = (int)match->data;
        >>>>> +
        >> [...]
        >>>> I'd prefer if you use the binding which requires no extra code in
        >>>> dwc2.
        >>> I'm fine with either option. However it think that this would require
        >>> that either Mark or Rob would allow an exception to the "keep existing
        >>> dts the way they are) and ack the following change to the canyonlands.dts. 
        >>
        >> I don't know about that. Under what circumstance can the dts change?
        > As far as I know, the justification for not changing the DTS is that a
        > compiled DTB might be stored in an read-only ROM on a board. So it would
        > be impossible to update it. Hence, the driver have work with the existing
        > (and sometimes buggy or incomplete) information to stay compatible.
        > 
        > (Note: Thankfully, the canyonlands dtb is stored in flash, it's possible
        > to update it. But it is an extra step that's not done automatically
        > with make install). 
        > 
        >> The canyonlands dts was binding to an external vendor driver. So it
        >> wasn't documented nor expected to work with dwc2 until your recent
        >> patch adding the compatible string.
        > 
        > Oh, no that's not what happend. Let me explain why there was no "external 
        > vendor driver": AMCC/APM were planing to upstream their hole platform. And
        > in fact, the devs tried very hard to include their driver back in 2011 [0].
        > But this driver was denied inclusion back then due to:
        > 
        > "[...]
        > I would also like to point out that the same Synopsys USB controller
        > is used in a number of other SoCs (especially ARM chips), and
        > supported by other drivers, some of these even in mainline.
        > 
        > See http://thread.gmane.org/gmane.linux.usb.general/61714/focus=62139
        > for a related thread.
        > 
        > Instead of trying to add a completely new driver to mainline (and one
        > which has been repeatedly been rejected), I vote for focusing on the
        > existing driver code that is already in mainline, and testing and
        > improving this so we can use a single implementation of this driver
        > code for all SoCs that use the same IP block." [1]
        > 
        > Of course: The listed link goes the "USB Host driver for i.MX28" driver.
        > And this is an ehci-hcd like driver... Which is as you are well aware not
        > that similar to the dwc2 OTG. And as far as I can tell: AMCC abandoned
        > the patch series right there. 
        > 
        > Note: AMCC did however succeed in pushing your employer's Synopsys
        > DesignWare SATA and DMA drivers to the kernel back then. And I'm happy
        > to report that both drivers are still around and working fine for the 460EX 
        > (sata_dwc_460ex.c[2] and the DW AHB DMA [3]). (The drivers also work for
        > different platforms than the original PPC. I know that because I helped
        > Andy Shevchenko with testing and pushing some fixes to it when he was
        > adding support for the Intel Quark SoC, which uses the DWC SATA and DMA).
        
        Ok thanks for clearing that up. I understand.
        
        For now we can just set the property to "INCR16" based on the
        compatible string. Perhaps in the future do this from a glue-layer
        driver which binds to all compatible strings other than "snps,dwc2".
        
        I won't be able to do anything with this until next week though.
        
        Regards,
        John
        
        ^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2016-11-29  3:32 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
     [not found] <cover.1479339900.git.johnyoun@synopsys.com>
     [not found] ` <6396482.jQaH1ArAfZ@debian64>
     [not found]   ` <e01e1b30-a399-94cc-33c9-625008b31d4b@synopsys.com>
2016-11-21 21:10     ` [PATCH v2 2/4] usb: dwc2: Add binding for AHB burst Christian Lamparter
2016-11-22  3:32       ` John Youn
2016-11-22 20:51         ` Christian Lamparter
2016-11-22 21:46           ` Rob Herring
2016-11-29  3:32           ` John Youn

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox