Re: [PATCH V2 04/11] drm/bridge: tc358767: Implement atomic_check callback

[Marek Vasut <marex@denx.de>]

On 2/21/22 10:01, Maxime Ripard wrote:
> On Sat, Feb 19, 2022 at 03:26:40AM +0100, Marek Vasut wrote:
>> On 2/18/22 18:34, Lucas Stach wrote:
>>
>> Hi
>>
>> [...]
>>
>>>>    drivers/gpu/drm/bridge/tc358767.c | 26 ++++++++++++++++++++++++++
>>>>    1 file changed, 26 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
>>>> index 522c2c4d8514f..01d11adee6c74 100644
>>>> --- a/drivers/gpu/drm/bridge/tc358767.c
>>>> +++ b/drivers/gpu/drm/bridge/tc358767.c
>>>> @@ -1289,6 +1289,31 @@ static bool tc_bridge_mode_fixup(struct drm_bridge *bridge,
>>>>    	return true;
>>>>    }
>>>> +static int tc_edp_common_atomic_check(struct drm_bridge *bridge,
>>>
>>> Drop the edp in the name here? Later in the series you call this
>>> function from the DPI code, so this breaks the nice clean naming
>>> separation from patch 1.
>>>
>>>> +				      struct drm_bridge_state *bridge_state,
>>>> +				      struct drm_crtc_state *crtc_state,
>>>> +				      struct drm_connector_state *conn_state,
>>>> +				      const unsigned int max_khz)
>>>> +{
>>>> +	tc_bridge_mode_fixup(bridge, &crtc_state->mode,
>>>> +			     &crtc_state->adjusted_mode);
>>>> +
>>>> +	if (crtc_state->adjusted_mode.clock > max_khz)
>>>> +		crtc_state->adjusted_mode.clock = max_khz;
>>>
>>> I don't think this is correct. The adjusted most is just for minor
>>> adjustments if the bridge can not fully match the mode. If userspace
>>> supplies a invalid high modeclock I think it would be better to fail
>>> the atomic check -> return -EINVAL
>>
>> Maxime was telling me that returning -EINVAL from atomic_check is weird, so
>> maybe we should also wait for his opinion on this part.
> 
> That was in a completely different context?
> 
> Our discussion was about how you would propagate clock constraints
> across a pipeline, and I was telling you that it would be weird to
> return -EINVAL for a mode that was reported on a connector as supported
> (or even preferred).
> 
> My argument was for mode_valid to filter them out.
> 
> If your clock is way above what you can support on your device, then
> returning an error in atomic_check is the right thing to do.

Ah OK