Subject: [PATCH 2/7] usb: dwc3: adapt dwc3 core to use Generic PHY Framework

From: [email-masked] (Roger Quadros)
Date: Tue, 15 Oct 2013 17:03:50 +0300

On 10/15/2013 04:56 PM, Felipe Balbi wrote:
> Hi,
> 
> On Tue, Oct 15, 2013 at 04:48:51PM +0300, Roger Quadros wrote:
>> On 10/15/2013 04:19 PM, Felipe Balbi wrote:
>>> Hi,
>>>
>>> On Tue, Oct 15, 2013 at 03:10:42PM +0300, Roger Quadros wrote:
>>>>>>>>> @@ -665,6 +669,9 @@ struct dwc3 {
>>>>>>>>>  	struct usb_phy		*usb2_phy;
>>>>>>>>>  	struct usb_phy		*usb3_phy;
>>>>>>>>>  
>>>>>>>>> +	struct phy		*usb2_generic_phy;
>>>>>>>>> +	struct phy		*usb3_generic_phy;
>>>>>>>>> +
>>>>>>>>>  	void __iomem		*regs;
>>>>>>>>>  	size_t			regs_size;
>>>>>>>>>  
>>>>>>>>>
>>>>>>>
>>>>>>> Do you have any suggestions on how to get only individual PHYs? like only
>>>>>>> usb2phy or usb3phy?
>>>>>>
>>>>>> My earlier understanding was that both PHYs are needed only if .speed is "super-speed"
>>>>>> and only usb2phy is needed for "high-speed". But as per Vivek's email it seems
>>>>>> Samsung's exynos5 SoC doesn't need usb2phy for "super-speed".
>>>>>>
>>>>>> So to keeps things flexible, I can propose the following approach
>>>>>> - if speed == 'high-speed' usb2phy must be present. usb3phy will be ignored if supplied.
>>>>>> - if speed == 'super-speed' usb3phy must be present and usb2phy is optional but must be
>>>>>> initialized if supplied.
>>>>>> - if speed is not specified, we default to 'super-speed'.
>>>>>>
>>>>>> Felipe, does this address the issue you were facing with OMAP5?
>>>>>
>>>>> on OMAP5 we cannot skip USB3 PHY initialization. But then it becomes a
>>>>> question of supporting a test feature (in OMAP5 case it would be cool to
>>>>> force controller to lower speeds for testing) or coping with a broken
>>>>> DTS.
>>>>>
>>>>
>>>> I don't think we can protect ourselves from all possible broken
>>>> configurations of DTS.
>>>> I would vote for simplicity and maximum flexibility.
>>>>
>>>> So IMO we should just depend on DTS to provide the phys that are
>>>> needed by the platform.
>>>> In the driver we initialize whatever PHY is provided and don't
>>>> complain if any or even all PHYs are missing.
>>>
>>> considering that DTS is an ABI, I really think eventually we *will* have
>>> broken DTBs burned into ROM and we will have to find ways to work with
>>> those too. Same thing already happens today with ACPI tables.
>>>
>>>> If this is not good enough then could you please suggest an
>>>> alternative? Thanks.
>>>
>>> The alternative would be to mandate nop xceiv for the "missing" PHY, but
>>> that doesn't solve anything, really, as DTS authors might still forget
>>> about the NOP xceiv and you can argue that forcing NOP xceiv would be a
>>> SW configuration.
>>>
>>> So, perhaps we go with the approach that all PHYs are optional, and
>>> here's my original patch which makes USB3 PHY optional:
>>>
>>> commit 979b84f96e4b7559b596b2933ae198aba267f260
>>> Author: Felipe Balbi <[email-masked]>
>>> Date:   Sun Jun 30 18:39:23 2013 +0300
>>>
>>>     usb: dwc3: core: make USB3 PHY optional
>>>     
>>>     If we want a port to work at any speed lower
>>>     than Superspeed, it makes no sense to even
>>>     initialize/power up the USB3 transceiver,
>>>     provided it won't be used.
>>>     
>>>     We can use the oportunity to save some power
>>>     and leave the superspeed transceiver powered
>>>     off.
>>>     
>>>     There is at least one such case which is
>>>     Texas Instruments' AM437x which has one
>>>     of its USB3 ports without a matching USB3
>>>     PHY (that port is hardwired to work on USB2
>>>     only).
>>>     
>>>     Signed-off-by: Felipe Balbi <[email-masked]>
>>>
>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>>> index 74f9cf0..7a5ab93 100644
>>> --- a/drivers/usb/dwc3/core.c
>>> +++ b/drivers/usb/dwc3/core.c
>>> @@ -387,16 +387,34 @@ static int dwc3_probe(struct platform_device *pdev)
>>>  	if (node) {
>>>  		dwc->maximum_speed = of_usb_get_maximum_speed(node);
>>>  
>>> -		dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 0);
>>> -		dwc->usb3_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 1);
>>> +		switch (dwc->maximum_speed) {
>>> +		case USB_SPEED_SUPER:
>>> +			dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 0);
>>> +			dwc->usb3_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 1);
>>> +			break;
>>> +		case USB_SPEED_HIGH:
>>> +		case USB_SPEED_FULL:
>>> +		case USB_SPEED_LOW:
>>> +			dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 0);
>>> +			break;
>>> +		}
>>>  
>>>  		dwc->needs_fifo_resize = of_property_read_bool(node, "tx-fifo-resize");
>>>  		dwc->dr_mode = of_usb_get_dr_mode(node);
>>>  	} else if (pdata) {
>>>  		dwc->maximum_speed = pdata->maximum_speed;
>>>  
>>> -		dwc->usb2_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB2);
>>> -		dwc->usb3_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB3);
>>> +		switch (dwc->maximum_speed) {
>>> +		case USB_SPEED_SUPER:
>>> +			dwc->usb2_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB2);
>>> +			dwc->usb3_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB3);
>>> +			break;
>>> +		case USB_SPEED_HIGH:
>>> +		case USB_SPEED_FULL:
>>> +		case USB_SPEED_LOW:
>>> +			dwc->usb2_phy = devm_usb_get_phy(dev, USB_PHY_TYPE_USB2);
>>> +			break;
>>> +		}
>>
>> What if we try to get both PHYs irrespective of 'maximum_speed' but based
>> on presence of phandle/pdata. That way there is some control in the adaptation code (dts/pdata)
>> as to which PHYs needs to be initialized for that particular instance.
>>
>> This is because there doesn't seem to be a consensus between different designs.
>> e.g. omap5 needs both phys for 'high-speed' whereas exynos5250 needs just the
>> usb3 phy for 'super-speed'
> 
> sure, can you write such a patch ? If it gets to my inbox in a couple
> hours I guess I can still review and take it upstream on v3.13,
> otherwise it's only on v3.14 :-(

As this patch from Kishon is already touching this area, it would be best if
he can send a v2 with this feature.

cheers,
-roger