linux-kernel - Re: [PATCH V1] pinctrl: qcom: spmi-gpio: Add support for qcom,gpios-disallowed property

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Date:   Tue, 29 Aug 2017 10:04:07 +0800
From:   Fenglin Wu <fenglinw@...eaurora.org>
To:     Shawn Guo <shawnguo@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        bjorn.andersson@...aro.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        collinsd@...eaurora.org, aghayal@...eaurora.org,
        wruan@...eaurora.org, kgunda@...eaurora.org
Subject: Re: [PATCH V1] pinctrl: qcom: spmi-gpio: Add support for
 qcom,gpios-disallowed property

On 8/29/2017 9:51 AM, Shawn Guo wrote:
> On Tue, Aug 29, 2017 at 09:03:02AM +0800, Fenglin Wu wrote:
>> I agree the GPIO's ownership is configurable and it always configured at
>> the very beginning of the device boot up which is not visible by linux
>> kernel drivers/image. Normally, this configuration is fixed in one
>> platform and it's been protected and not allowed to be configured in
>> linux kernel driver. So from linux driver point of view, this is a
>> hardware configuration. I agree the coming patch "spmi: pmic-arb: Move
>> the ownership check to irq_chip callback" would fix the pinctrl-
>> spmi-gpio driver probe failure caused by the ownership mismatch, but
>> this is just hiding the mistake of the kernel configured the GPIOs which
>> not owned by APPS processor.
> 
> The kernel does everything just right, using the GPIO that device tree
> tells to use.  If there is something wrong about ownership check, it
> should be fault of that device tree specifies the wrong GPIO, or
> firmware doesn't configure ownership as needed.
> > Shawn
> 

If you thought that the driver registers pins for the GPIOs not owned by
APPS processor is correct, then this patch is no needed.
I agreed with others.
Thanks

Fenglin

>> And these GPIOs will be registered
>> successfully as pinctrl pins and any APPS processor consumer drivers
>> could use this pins. This is not correct even the select_state operation
>> for these pins would failed due to the mode protection in spmi write_cmd
>> calling. I am thinking that not allowing these pins to be register as
>> pinctrl pins should be more straightforward and easy understanding. So I
>> think this patch still have value even the probe failure has been fixed
>> by the coming spmi patch.

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