linux-kernel - Re: [PATCH] gpio: gpio-rcar: init at postcore level

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Message-ID: <CANqRtoRnE=E=8Njd1UcfnjevxDf-7Xt1dBv0FZg+Kww7ZCTwEw@mail.gmail.com>
Date:	Mon, 24 Feb 2014 16:55:16 +0900
From:	Magnus Damm <magnus.damm@...il.com>
To:	Vladimir Barinov <vladimir.barinov@...entembedded.com>
Cc:	SH-Linux <linux-sh@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-gpio <linux-gpio@...r.kernel.org>,
	"Simon Horman [Horms]" <horms@...ge.net.au>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Subject: Re: [PATCH] gpio: gpio-rcar: init at postcore level

Hi Vladimir,

On Mon, Feb 24, 2014 at 4:42 PM, Vladimir Barinov
<vladimir.barinov@...entembedded.com> wrote:
> Hi Magnus,
>
>
> On 02/24/2014 06:57 AM, Magnus Damm wrote:
>>
>> Hi Vladimir,
>>
>> On Mon, Feb 24, 2014 at 1:37 AM,<vladimir.barinov@...entembedded.com>
>> wrote:
>>>
>>> From: Vladimir Barinov<vladimir.barinov@...entembedded.com>
>>>
>>> This adds ability to use gpio API at board init_machine level.
>>>
>>> F.e. it can be used in the following situation.
>>> Many reference hardware has onboard switches that selects which
>>> periferals
>>> to connect to the system. The gpio input state from switches can be used
>>> in choosing platform devices runtime in board code instead of
>>> ifdefs/defconfig
>>> changes.
>>>
>>> Signed-off-by:<vladimir.barinov@...entembedded.com>
>>>
>>> ---
>>>   drivers/gpio/gpio-rcar.c |   12 +++++++++++-
>>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>>
>>> Index: build/drivers/gpio/gpio-rcar.c
>>> ===================================================================
>>> --- build.orig/drivers/gpio/gpio-rcar.c 2014-02-22 23:21:51.456229152
>>> +0400
>>> +++ build/drivers/gpio/gpio-rcar.c      2014-02-22 23:21:52.320229133
>>> +0400
>>> @@ -485,7 +485,17 @@
>>>          }
>>>   };
>>>
>>> -module_platform_driver(gpio_rcar_device_driver);
>>> +static int __init gpio_rcar_init(void)
>>> +{
>>> +       return platform_driver_register(&gpio_rcar_device_driver);
>>> +}
>>> +postcore_initcall(gpio_rcar_init);
>>> +
>>> +static void __exit gpio_rcar_exit(void)
>>> +{
>>> +       platform_driver_unregister(&gpio_rcar_device_driver);
>>> +}
>>> +module_exit(gpio_rcar_exit);
>>>
>>>   MODULE_AUTHOR("Magnus Damm");
>>>   MODULE_DESCRIPTION("Renesas R-Car GPIO Driver");
>>
>> Hi Vladimir,
>>
>> Thanks for your help. Good to see that you are working on enabling the
>> dual role USB port on Koelsch.
>>
>> Your current board code is checking some DIP switch value during boot,
>> and that kind of early use of GPIO would require a change in the probe
>> order like this patch implements. I do however believe that we should
>> not implement checking during boot like this.
>>
>> If you for instance check the legacy Lager USBHS DIP switch code that
>> runs during driver probe() then that can run can use GPIO without the
>> need for a change like this. So your GPIO user code needs to be
>> adjusted.
>
> Yes, this is true for USBHS that has platform callbacks like
> hardware_init/exit.
> But this is not acceptable for other devices like EHCI PCI/PHY and others.
> So we wouldn't be able to do such fixup for other cases.

Right, the USBHS driver has callbacks but PCI-based hardrware like
EHCI and OHCI do not have such. But I believe we already have some
kind of USB PHY abstraction level and we also have a R-Car Gen2 PHY
driver that somehow is integrated together with the PCI-based
hardware. Based on that my feeling is that the answer to ID-pin
control is there somewhere, and not just once during the boot! =)

Cheers,

/ magnus
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