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Subject: Re: [PATCH stable] gpiolib: Read "gpio-line-names" from a firmware
 node
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Bartosz Golaszewski <brgl@bgdev.pl>
Cc:     linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        stable@vger.kernel.org, Roman Guskov <rguskov@dh-electronics.com>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
References: <20210410090919.3157-1-brgl@bgdev.pl> <YHGVE1hMDUiK0P2A@kroah.com>
From:   Marek Vasut <marex@denx.de>
Message-ID: <e76d59f9-37ff-b31e-0131-113a1eedd786@denx.de>
Date:   Sat, 10 Apr 2021 15:20:57 +0200
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On 4/10/21 2:07 PM, Greg Kroah-Hartman wrote:
> On Sat, Apr 10, 2021 at 11:09:19AM +0200, Bartosz Golaszewski wrote:
>> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>>
>> On STM32MP1, the GPIO banks are subnodes of pin-controller@50002000,
>> see arch/arm/boot/dts/stm32mp151.dtsi. The driver for
>> pin-controller@50002000 is in drivers/pinctrl/stm32/pinctrl-stm32.c
>> and iterates over all of its DT subnodes when registering each GPIO
>> bank gpiochip. Each gpiochip has:
>>
>>    - gpio_chip.parent = dev,
>>      where dev is the device node of the pin controller
>>    - gpio_chip.of_node = np,
>>      which is the OF node of the GPIO bank
>>
>> Therefore, dev_fwnode(chip->parent) != of_fwnode_handle(chip.of_node),
>> i.e. pin-controller@50002000 != pin-controller@50002000/gpio@5000*000.
>>
>> The original code behaved correctly, as it extracted the "gpio-line-names"
>> from of_fwnode_handle(chip.of_node) = pin-controller@50002000/gpio@5000*000.
>>
>> To achieve the same behaviour, read property from the firmware node.
>>
>> Fixes: 7cba1a4d5e162 ("gpiolib: generalize devprop_gpiochip_set_names() for device properties")
>> Cc: stable@vger.kernel.org
>> Reported-by: Marek Vasut <marex@denx.de>
>> Reported-by: Roman Guskov <rguskov@dh-electronics.com>
>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>> Tested-by: Marek Vasut <marex@denx.de>
>> Reviewed-by: Marek Vasut <marex@denx.de>
>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>> ---
>> Hi Greg,
>>
>> This patch somehow got lost and never made its way into stable. Could you
>> please apply it?
> 
> This has been added and removed more times than I can remember already.
> 
> Are you all _SURE_ this is safe for a stable kernel release?  Look in
> the archives for complaints when we added this in the past.

I now tested this on stm32mp1, which was the original platform that got 
affected by the problem this is supposed to fix, and I can confirm this 
patch fixes the problem there.

So for what it's worth
Tested-by: Marek Vasut <marex@denx.de> # on stm32mp1