Re: [PATCH v10 4/4] arm64: dts: qcom: qcs6490-rb3gen2-vision-mezzanine: Add vision mezzanine

[Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>]

On 12/19/24 21:06, Konrad Dybcio wrote:
> On 17.12.2024 3:40 PM, Vladimir Zapolskiy wrote:
>> On 12/17/24 16:06, Vikram Sharma wrote:
>>> The Vision Mezzanine for the RB3 ships with an imx577 camera sensor.
>>> Enable the IMX577 on the vision mezzanine.
>>>
>>> An example media-ctl pipeline for the imx577 is:
>>>
>>> media-ctl --reset
>>> media-ctl -v -V '"imx577 '19-001a'":0[fmt:SRGGB10/4056x3040 field:none]'
>>> media-ctl -V '"msm_csiphy3":0[fmt:SRGGB10/4056x3040]'
>>> media-ctl -V '"msm_csid0":0[fmt:SRGGB10/4056x3040]'
>>> media-ctl -V '"msm_vfe0_rdi0":0[fmt:SRGGB10/4056x3040]'
>>> media-ctl -l '"msm_csiphy3":1->"msm_csid0":0[1]'
>>> media-ctl -l '"msm_csid0":1->"msm_vfe0_rdi0":0[1]'
>>>
>>> yavta -B capture-mplane -c -I -n 5 -f SRGGB10P -s 4056x3040 -F /dev/video0
>>>
>>> Signed-off-by: Hariram Purushothaman <quic_hariramp@quicinc.com>
>>> Signed-off-by: Vikram Sharma <quic_vikramsa@quicinc.com>
>>> Signed-off-by: Trishansh Bhardwaj <quic_tbhardwa@quicinc.com>
>>> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
>>> Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>>> ---
> 
> [...]
> 
>>> +        rst-pins {
>>> +            pins = "gpio78";
>>> +            function = "gpio";
>>> +            drive-strength = <2>;
>>> +            bias-pull-down;
>>> +            output-low;
>>> +        };
>>
>> I have doubts that it's proper to embed a reset gpio into driver's
>> pinctrl suspend/resume power management.
>>
>> Konrad, can you please confirm that it's really accepted?
>>
>> I'd rather ask to remove this reset pin control.
> 
> There's certainly some appearances of this in the tree.
> 
> You could make the argument that it makes sense to prevent misconfiguration
> (i.e. the bootloader may set the pin in input mode), but then the counter
> argument is that the (Linux) gpiod APIs request OUT_LOW/HIGH, and we would
> expect that the driver uses that if the GPIO is requested through
> e.g. reset-gpios.
> 
> I'm not particularly sure what to recommend here. Krzysztof?
> 

I'm worried by a possibility that a device reset/shutdown control GPIO could
be turned off by entering the "sleep" pinctrl setup. If a particular GPIO/pin
is off, is it still continuously functional as a control GPIO of some device?
I believe it is not anymore in general, this is my concern here.

--
Best wishes,
Vladimir