Re: [PATCH v3 4/6] drm: Use new mode_valid() helpers in connector probe helper

[Andrzej Hajda]

On 15.05.2017 11:30, Daniel Vetter wrote:
> On Mon, May 15, 2017 at 10:39:35AM +0200, Andrzej Hajda wrote:
>> On 11.05.2017 11:06, Jose Abreu wrote:
>>> This changes the connector probe helper function to use the new
>>> encoder->mode_valid(), bridge->mode_valid() and crtc->mode_valid()
>>> helper callbacks to validate the modes.
>>>
>>> The new callbacks are optional so the behaviour remains the same
>>> if they are not implemented. If they are, then the code loops
>>> through all the connector's encodersXbridgesXcrtcs and calls the
>>> callback.
>>>
>>> If at least a valid encoderXbridgeXcrtc combination is found which
>>> accepts the mode then the function returns MODE_OK.
>>>
>>> Signed-off-by: Jose Abreu <joabreu@xxxxxxxxxxxx>
>>> Cc: Carlos Palminha <palminha@xxxxxxxxxxxx>
>>> Cc: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
>>> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>>> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
>>> Cc: Dave Airlie <airlied@xxxxxxxx>
>>> Cc: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
>>> Cc: Archit Taneja <architt@xxxxxxxxxxxxxx>
>>> ---
>>>
>>> Changes v2->v3:
>>> 	- Call also bridge->mode_valid (Daniel)
>>> Changes v1->v2:
>>> 	- Use new helpers suggested by Ville
>>> 	- Change documentation (Daniel)
>>>
>>>  drivers/gpu/drm/drm_probe_helper.c | 65 ++++++++++++++++++++++++++++++++++++--
>>>  1 file changed, 62 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
>>> index f01abdc..84d660e 100644
>>> --- a/drivers/gpu/drm/drm_probe_helper.c
>>> +++ b/drivers/gpu/drm/drm_probe_helper.c
>>> @@ -83,6 +83,61 @@
>>>  	return MODE_OK;
>>>  }
>>>  
>>> +static enum drm_mode_status
>>> +drm_mode_validate_connector(struct drm_connector *connector,
>>> +			    struct drm_display_mode *mode)
>>> +{
>>> +	struct drm_device *dev = connector->dev;
>>> +	uint32_t *ids = connector->encoder_ids;
>>> +	enum drm_mode_status ret = MODE_OK;
>>> +	unsigned int i;
>>> +
>>> +	/* Step 1: Validate against connector */
>>> +	ret = drm_connector_mode_valid(connector, mode);
>>> +	if (ret != MODE_OK)
>>> +		return ret;
>>> +
>>> +	/* Step 2: Validate against encoders and crtcs */
>>> +	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
>>> +		struct drm_encoder *encoder = drm_encoder_find(dev, ids[i]);
>>> +		struct drm_crtc *crtc;
>>> +
>>> +		if (!encoder)
>>> +			continue;
>>> +
>>> +		ret = drm_encoder_mode_valid(encoder, mode);
>>> +		if (ret != MODE_OK) {
>>> +			/* No point in continuing for crtc check as this encoder
>>> +			 * will not accept the mode anyway. If all encoders
>>> +			 * reject the mode then, at exit, ret will not be
>>> +			 * MODE_OK. */
>>> +			continue;
>>> +		}
>>> +
>>> +		ret = drm_bridge_mode_valid(encoder->bridge, mode);
>>> +		if (ret != MODE_OK) {
>>> +			/* There is also no point in continuing for crtc check
>>> +			 * here. */
>>> +			continue;
>>> +		}
>> Maybe it is a bikeshedding, but wouldn't be better to call
>> drm_bridge_mode_valid from drm_encoder_mode_valid, in general call all
>> bridge related stuff from corresponding encoder stuff?
>> This is more question about role of encoder->bridge, should it be
>> treated as encoder's extension, or as 1st class citizen in drm?
>>
>> Another concern is about order of calls, it is from sink to source, to
>> keep it consistent bridge should be called before encoder, am I right?
> For the atomic_check stuff (where we do change the passed-in mode) this
> would be correct, and calling order and layering would matter. But this
> just validates the mode in turn with everything, not taking any
> cross-component constraint or other configuration-dependent constraints
> into account. Hence it doesn't matter in which order we call stuff.
>
> Note that the passed-in mode is const, so you can't escape. And v3 of
> patch 1 now has added wording that you're not allowed to look at anything
> else dynamie either.
>
> Does that address your concern?

Yes, I know it practically does not matter. I have mistakenly written
"Beside this: R-b", it should be rather "Anyway: R-b" :)

Regards
Andrzej

> -Daniel
>
>> Beside this:
>> Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
>>
>>  --
>> Regards
>> Andrzej
>>
>>> +
>>> +		drm_for_each_crtc(crtc, dev) {
>>> +			if (!drm_encoder_crtc_ok(encoder, crtc))
>>> +				continue;
>>> +
>>> +			ret = drm_crtc_mode_valid(crtc, mode);
>>> +			if (ret == MODE_OK) {
>>> +				/* If we get to this point there is at least
>>> +				 * one combination of encoder+crtc that works
>>> +				 * for this mode. Lets return now. */
>>> +				return ret;
>>> +			}
>>> +		}
>>> +	}
>>> +
>>> +	return ret;
>>> +}
>>> +
>>>  static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
>>>  {
>>>  	struct drm_cmdline_mode *cmdline_mode;
>>> @@ -322,7 +377,11 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
>>>   *    - drm_mode_validate_flag() checks the modes against basic connector
>>>   *      capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
>>>   *    - the optional &drm_connector_helper_funcs.mode_valid helper can perform
>>> - *      driver and/or hardware specific checks
>>> + *      driver and/or sink specific checks
>>> + *    - the optional &drm_crtc_helper_funcs.mode_valid,
>>> + *      &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
>>> + *      helpers can perform driver and/or source specific checks which are also
>>> + *      enforced by the modeset/atomic helpers
>>>   *
>>>   * 5. Any mode whose status is not OK is pruned from the connector's modes list,
>>>   *    accompanied by a debug message indicating the reason for the mode's
>>> @@ -466,8 +525,8 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
>>>  		if (mode->status == MODE_OK)
>>>  			mode->status = drm_mode_validate_flag(mode, mode_flags);
>>>  
>>> -		if (mode->status == MODE_OK && connector_funcs->mode_valid)
>>> -			mode->status = connector_funcs->mode_valid(connector,
>>> +		if (mode->status == MODE_OK)
>>> +			mode->status = drm_mode_validate_connector(connector,
>>>  								   mode);
>>>  	}
>>>  
>>