From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2 3/4] usb: chipidea: ci13xxx-imx: add "dr_mode" property to device tree bindings
Date: Mon, 02 Jul 2012 14:04:12 -0600 [thread overview]
Message-ID: <4FF1FEBC.3040107@wwwdotorg.org> (raw)
In-Reply-To: <20120630011906.GA2489@richard-laptop>
On 06/29/2012 07:19 PM, Richard Zhao wrote:
> On Fri, Jun 29, 2012 at 09:51:49AM -0600, Stephen Warren wrote:
>> On 06/29/2012 02:45 AM, Richard Zhao wrote:
>>> On Fri, Jun 29, 2012 at 09:47:03AM +0200, Marc Kleine-Budde wrote:
>>>>
>>>> Cc'ed Devicetree Discussions
>>>>
>>>> On 06/29/2012 03:43 AM, Richard Zhao wrote:
>>>>> On Thu, Jun 28, 2012 at 03:53:48PM +0200, Marc Kleine-Budde wrote:
>>>>>> This patch allows the device tree to limit the chipidea to host or
>>>>>> peripheral mode only.
>>>>>>
>>>>>> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix•de>
>>>>>> ---
>>>>>> .../devicetree/bindings/usb/ci13xxx-imx.txt | 3 ++
>>>>>> drivers/usb/chipidea/ci13xxx_imx.c | 3 ++
>>>>>> drivers/usb/chipidea/core.c | 41 +++++++++++++++++---
>>>>>> include/linux/usb/chipidea.h | 9 +++++
>>>>>> 4 files changed, 50 insertions(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/usb/ci13xxx-imx.txt b/Documentation/devicetree/bindings/usb/ci13xxx-imx.txt
>>>>>> index 5a0ad66..67f97f56 100644
>>>>>> --- a/Documentation/devicetree/bindings/usb/ci13xxx-imx.txt
>>>>>> +++ b/Documentation/devicetree/bindings/usb/ci13xxx-imx.txt
>>>>>> @@ -4,6 +4,8 @@ Required properties:
>>>>>> - compatible: Should be "fsl,imx27-usb"
>>>>>> - reg: Should contain registers location and length
>>>>>> - interrupts: Should contain controller interrupt
>>>>>> +- dr_mode: indicates the working mode for compatible controllers. Can
>>>>>> + be "host", "peripheral", or "otg". Defaults to "otg" if not defined.
>>>>
>>>>> By default, it should be decided by capability registers. Only bad hw
>>>>> design needs such settings. So, why not name it as force-xxx? If it's
>>>>> not specific to imx, it doesn't needs to has prefix "fsl,".
>>>>
>>>> It's not a bad hardware design if you don't route or enable all ports a
>>>> soc offers. In modern socs you cannot enable all ports anyway.
>>>
>>> I'm not sure about your case, but generally, it's not about ports.
>>> It's about ID pin. If ID pin is not connect correctly, we may need to
>>> force it to host or device working mode. The 'force" here means it
>>> won't follow the capability registers and ID pin.
>>>>
>>>> The property isn't prefixed with "fsl,", it's just "dr_mode".
>>>>
>>>> Why not "force-xxx"? I had a look at Documentation/devicetree/bindings/usb:
>>>>
>>>> tegra-usb.txt:
>>>>> - dr_mode : dual role mode. Indicates the working mode for
>>>>> nvidia,tegra20-ehci compatible controllers. Can be "host", "peripheral",
>>>>> or "otg". Default to "host" if not defined for backward compatibility.
>>>>> host means this is a host controller
>>>>> peripheral means it is device controller
>>>>> otg means it can operate as either ("on the go")
>>>>
>>>> fsl-usb.txt:
>>>>> - dr_mode : indicates the working mode for "fsl-usb2-dr" compatible
>>>>> controllers. Can be "host", "peripheral", or "otg". Default to
>>>>> "host" if not defined for backward compatibility.
>>>>>
>>>>
>>>> So why invent something new, if there seems to be a pattern?
>>>
>>> I'm not sure they mean the same things, because the default value is
>>> different. Event if they're same, why not make them all with sensible
>>> name?
>>
>> I'm not quite sure what the question is I'm being asked here.
>>
>> I certainly think that new bindings should follow existing precedent
>> where possible for representing the same data. dr_mode is that precedent
>> for a USB host's operating mode. Tegra chose to use that because of
>> precedent in fsl-usb.txt IIRC.
>
> For imx, in most cases, we don't use dr_mode. The role is decided by
> CAP_DCCPARAMS and ID pin. For tegra and fsl-usb, it looks like the role
> is totally decided by dt property. So I suggested use force-xxx to let
> everyone know it does not follow the default action. I don't quite
> insist on the naming, because dr_mode is similar (not same).
Hmm. I think it'd be reasonable to use dr_mode like the other bindings,
and have the default case be decided by the ID pin when dr_mode isn't
specified. Having different defaults for different bindings seems pretty
reasonable to me.
next prev parent reply other threads:[~2012-07-02 20:04 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-28 13:53 [PATCH v2 0/4] usb: chipidea: fix error handling and add dr_role property Marc Kleine-Budde
2012-06-28 13:53 ` [PATCH v2 1/4] usb: chipidea: pci: make platformdata static Marc Kleine-Budde
2012-06-28 14:06 ` Richard Zhao
2012-07-08 15:10 ` Richard Zhao
2012-07-08 17:48 ` Russell King - ARM Linux
2012-07-09 1:20 ` Richard Zhao
2012-06-28 13:53 ` [PATCH v2 2/4] usb: chipidea: udc: fix error path in udc_start() Marc Kleine-Budde
2012-06-28 13:53 ` [PATCH v2 3/4] usb: chipidea: ci13xxx-imx: add "dr_mode" property to device tree bindings Marc Kleine-Budde
2012-06-29 1:43 ` Richard Zhao
2012-06-29 7:47 ` Marc Kleine-Budde
2012-06-29 8:45 ` Richard Zhao
2012-06-29 9:29 ` Marc Kleine-Budde
2012-06-30 1:40 ` Richard Zhao
2012-06-29 15:51 ` Stephen Warren
2012-06-30 1:19 ` Richard Zhao
2012-07-02 20:04 ` Stephen Warren [this message]
2012-07-03 2:22 ` Peter Chen
2012-07-03 3:00 ` Richard Zhao
2012-07-03 7:02 ` Lothar Waßmann
2012-07-03 7:10 ` Richard Zhao
2012-06-30 1:33 ` Richard Zhao
2012-06-30 21:57 ` Sergei Shtylyov
2012-06-28 13:53 ` [PATCH v2 4/4] ARM: dts: imx23,28: limit usb to host role Marc Kleine-Budde
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