Re: [PATCH v2 2/2] media: imx335: Fix reset-gpio handling

[Krzysztof Kozlowski <krzk@kernel.org>]

On 31/07/2024 11:02, Kieran Bingham wrote:
> Quoting Umang Jain (2024-07-31 06:41:35)
>> Hi all,
>>
>> On 30/07/24 2:40 pm, Laurent Pinchart wrote:
>>> On Tue, Jul 30, 2024 at 10:42:01AM +0200, Krzysztof Kozlowski wrote:
>>>> On 30/07/2024 10:24, Sakari Ailus wrote:
>>>>> Hi Krzysztof,
>>>>>
>>>>> On Mon, Jul 29, 2024 at 04:09:39PM +0200, Krzysztof Kozlowski wrote:
>>>>>> On 29/07/2024 13:04, Umang Jain wrote:
>>>>>>> Rectify the logical value of reset-gpio so that it is set to
>>>>>>> 0 (disabled) during power-on and to 1 (enabled) during power-off.
>>>>>>>
>>>>>>> Meanwhile at it, set the reset-gpio to GPIO_OUT_HIGH at initialization
>>>>>>> time to make sure it starts off in reset.
>>>>>>>
>>>>>>> Fixes: 45d19b5fb9ae ("media: i2c: Add imx335 camera sensor driver")
>>>>>>> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
>>>>>>> ---
>>>>>>>   drivers/media/i2c/imx335.c | 8 ++++----
>>>>>>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>>>>>>
>>>>>> This will break all the users, so no. At least not without mentioning
>>>>>> ABI break and some sort of investigating how customers or users are
>>>>>> affected.
>>>>> I know the original authors aren't using the driver anymore and it took
>>>>> quite a bit of time until others started to contribute to it so I suspect
>>>>> the driver hasn't been in use for that long. There are no instances of the
>>>>> device in the in-kernel DTS either.
>>>>>
>>>>> Any DTS author should have also noticed the issue but of course there's a
>>>>> risk someone could have just changed the polarity and not bothered to chech
>>>>> what it was supposed to be.
>>>>>
>>>>> I agree the commit message should be more vocal about the effects on
>>>>> existing DTS.
>>>> I can imagine that all users (out of tree, in this case) inverted
>>>> polarity in DTS based on what's implemented. You could go with some
>>>> trivial hack, like I did for one of codecs - see 738455858a2d ("ASoC:
>>>> codecs: wsa881x: Use proper shutdown GPIO polarity"), but I remember
>>>> Mark Brown rejected similar commit for newer drivers.
>>> I don't think there's any out-of-tree user, because when we started
>>> using the recently driver, it required lots of fixes to even work at
>>> all. I'll let Kieran and Umang comment on that, I haven't follow the
>>> development in details.
>>
>> indeed, initially we had to put up fixes like :
>>
>> 14a60786d72e ("media: imx335: Set reserved register to default value")
>> 81495a59baeba ("media: imx335: Fix active area height discrepency")
>>
>> to make the sensor work properly on our platforms. Only after that we 
>> had a base to support more capabilities on the sensor (multiple lanes 
>> support, flips, TPG etc.)
> 
> I would also add that we had to provide control for the regulators to be
> able to power the device as well in fea91ee73b7c ("media: i2c: imx335:
> Enable regulator supplies").

Hm? That's not a proof of anything. Supplies are often turned on by default.

> 
> Given the driver was posted from Intel, I would have anticipated perhaps
> the driver was in fact only actually tested by Intel on ACPI platforms -
> yet with no ACPI table registered in the driver - even that could likely
> be considered broken.

Nope, that does not work like that. Their platforms and such sensors are
often used on DT based boards. Not mentioning even PRP0001.

> 
> Based on that I have a high confidence that there are no current users
> of this driver (except us).

Nope, wrong conclusions, not that many arguments.



Best regards,
Krzysztof