linux-kernel - Re: [PATCH 3/5] gpio: vf610: add i.MX8ULP of_device

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Date:   Thu, 14 Sep 2023 11:39:54 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Peng Fan <peng.fan@....com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     "Peng Fan (OSS)" <peng.fan@....nxp.com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Andy Shevchenko <andy@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Stefan Agner <stefan@...er.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/5] gpio: vf610: add i.MX8ULP of_device_id entry

On 14/09/2023 11:08, Peng Fan wrote:
>> Subject: Re: [PATCH 3/5] gpio: vf610: add i.MX8ULP of_device_id entry
>>
>> On 14/09/2023 10:48, Linus Walleij wrote:
>>> On Thu, Sep 14, 2023 at 7:48 AM Krzysztof Kozlowski
>>> <krzysztof.kozlowski@...aro.org> wrote:
>>>> On 14/09/2023 04:20, Peng Fan (OSS) wrote:
>>>>> From: Peng Fan <peng.fan@....com>
>>>>>
>>>>> i.MX8ULP supports two interrupts, while i.MX7ULP supports one
>> interrupt.
>>>>> So from hardware perspective, they are not compatible.
>>>>>
>>>>> So add entry for i.MX8ULP.
>>>>>
>>>>> Signed-off-by: Peng Fan <peng.fan@....com>
>>>>> ---
>>>>>  drivers/gpio/gpio-vf610.c | 1 +
>>>>>  1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/drivers/gpio/gpio-vf610.c b/drivers/gpio/gpio-vf610.c
>>>>> index dbc7ba0ee72c..88f7215cdf4b 100644
>>>>> --- a/drivers/gpio/gpio-vf610.c
>>>>> +++ b/drivers/gpio/gpio-vf610.c
>>>>> @@ -67,6 +67,7 @@ static const struct fsl_gpio_soc_data imx_data = {
>>>>> static const struct of_device_id vf610_gpio_dt_ids[] = {
>>>>>       { .compatible = "fsl,vf610-gpio",       .data = NULL, },
>>>>>       { .compatible = "fsl,imx7ulp-gpio",     .data = &imx_data, },
>>>>> +     { .compatible = "fsl,imx8ulp-gpio",     .data = &imx_data, },
>>>>
>>>> Why? It is the same as imx7. No need.
>>>
>>> Because compatible = "fsl,imx7ulp-gpio" is not what is going to be in
>>> the device tree, but compatible = "fsl,imx8ulp-gpio"?
>>>
>>> What am I missing here? Maybe the commit message is weird.
>>>
>>
>> If the devices used before and are still going to use same driver data, they
>> look compatible from OS point of view. Therefore usually we express such
>> compatibility and do not add unneeded device_id entries.
>>
>> Now whether the devices are truly compatible or not, I don't know and with
>> some recent emails I am bit confused.
> 
> Some tricks in dtb are made to make the driver could work for both i.MX7ULP,
> i.MX8ULP, i.MX93 with fsl,imx7ulp-gpio.
> 
> Such as i.MX8ULP:
> reg = <0x2d000080 0x1000>, <0x2d000040 0x40>;
> Actually the two regs are belong to one physical continuous space,
> <0x2d000000 0x1000>
> Just to i.MX8ULP could reuse the vf610 gpio driver, the regs are partitioned
> into two with some offset added
> 
> So from hw, I think they are not compatible, just some sw tricks to
> make the linux driver could work for both platform.

OK, that sounds like reason to clean this up - drivers, bindings and
finally DTS - all with proper explanation justifying affected DTS users.

Best regards,
Krzysztof