[PATCH v4 03/20] drm: allow real encoder to be passed for drm_writeback_connector

[Abhinav Kumar]

Hi Laurent

On 4/24/2022 7:50 AM, Laurent Pinchart wrote:
> Hi Abhinav,
> 
> Thank you for the patch.
> 
> On Fri, Apr 22, 2022 at 04:06:38PM -0700, Abhinav Kumar wrote:
>> For some vendor driver implementations, display hardware can
>> be shared between the encoder used for writeback and the physical
>> display.
>>
>> In addition resources such as clocks and interrupts can
>> also be shared between writeback and the real encoder.
>>
>> To accommodate such vendor drivers and hardware, allow
>> real encoder to be passed for drm_writeback_connector.
>>
>> For existing clients, drm_writeback_connector_init() will use
>> an internal_encoder under the hood and hence no changes will
>> be needed.
>>
>> changes in v7:
>> 	- move this change before the vc4 change in the series
>> 	  to minimize the changes to vendor drivers in drm core
>> 	  changes
> 
> Why is this needed ? The drm_writeback_connector functions don't need
> the drm_encoder after drm_writeback_connector_init() (or
> drm_writeback_connector_init_with_encoder()) returns.
> 

Sorry I didnt follow this comment. This change log is incorrect, so 
after changing the previous change in the series and modifying this, no 
further changes are needed to vc4, so I decided to drop the next change.
So this change log is incorrect. I can remove this.

Is that what you meant?

>> Signed-off-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
>> ---
>>   drivers/gpu/drm/drm_writeback.c | 18 ++++++++++++------
>>   drivers/gpu/drm/vc4/vc4_txp.c   |  4 ++--
>>   include/drm/drm_writeback.h     | 22 ++++++++++++++++++++--
>>   3 files changed, 34 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
>> index 92658ad..0538674 100644
>> --- a/drivers/gpu/drm/drm_writeback.c
>> +++ b/drivers/gpu/drm/drm_writeback.c
>> @@ -180,21 +180,21 @@ int drm_writeback_connector_init(struct drm_device *dev,
>>   {
>>   	int ret = 0;
>>   
>> -	drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
>> +	drm_encoder_helper_add(&wb_connector->internal_encoder, enc_helper_funcs);
>>   
>> -	wb_connector->encoder.possible_crtcs = possible_crtcs;
>> +	wb_connector->internal_encoder.possible_crtcs = possible_crtcs;
>>   
>> -	ret = drm_encoder_init(dev, &wb_connector->encoder,
>> +	ret = drm_encoder_init(dev, &wb_connector->internal_encoder,
>>   			       &drm_writeback_encoder_funcs,
>>   			       DRM_MODE_ENCODER_VIRTUAL, NULL);
>>   	if (ret)
>>   		return ret;
>>   
>> -	ret = drm_writeback_connector_init_with_encoder(dev, wb_connector, &wb_connector->encoder,
>> -			con_funcs, formats, n_formats);
>> +	ret = drm_writeback_connector_init_with_encoder(dev, wb_connector,
>> +			&wb_connector->internal_encoder, con_funcs, formats, n_formats);
>>   
>>   	if (ret)
>> -		drm_encoder_cleanup(&wb_connector->encoder);
>> +		drm_encoder_cleanup(&wb_connector->internal_encoder);
>>   
>>   	return ret;
>>   }
>> @@ -239,6 +239,12 @@ int drm_writeback_connector_init_with_encoder(struct drm_device *dev,
>>   	struct drm_mode_config *config = &dev->mode_config;
>>   	int ret = create_writeback_properties(dev);
>>   
>> +	/*
>> +	 * Assign the encoder passed to this API to the wb_connector's encoder.
>> +	 * For drm_writeback_connector_init(), this shall be the internal_encoder
>> +	 */
>> +	wb_connector->encoder = enc;
>> +
>>   	if (ret != 0)
>>   		return ret;
>>   
>> diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c
>> index 3447eb6..7e063a9 100644
>> --- a/drivers/gpu/drm/vc4/vc4_txp.c
>> +++ b/drivers/gpu/drm/vc4/vc4_txp.c
>> @@ -159,7 +159,7 @@ struct vc4_txp {
>>   
>>   static inline struct vc4_txp *encoder_to_vc4_txp(struct drm_encoder *encoder)
>>   {
>> -	return container_of(encoder, struct vc4_txp, connector.encoder);
>> +	return container_of(encoder, struct vc4_txp, connector.internal_encoder);
>>   }
>>   
>>   static inline struct vc4_txp *connector_to_vc4_txp(struct drm_connector *conn)
>> @@ -507,7 +507,7 @@ static int vc4_txp_bind(struct device *dev, struct device *master, void *data)
>>   	if (ret)
>>   		return ret;
>>   
>> -	encoder = &txp->connector.encoder;
>> +	encoder = txp->connector.encoder;
>>   	encoder->possible_crtcs = drm_crtc_mask(crtc);
>>   
>>   	ret = devm_request_irq(dev, irq, vc4_txp_interrupt, 0,
>> diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
>> index bb306fa..3fbae9d 100644
>> --- a/include/drm/drm_writeback.h
>> +++ b/include/drm/drm_writeback.h
>> @@ -25,13 +25,31 @@ struct drm_writeback_connector {
>>   	struct drm_connector base;
>>   
>>   	/**
>> -	 * @encoder: Internal encoder used by the connector to fulfill
>> +	 * @encoder: handle to drm_encoder used by the connector to fulfill
>>   	 * the DRM framework requirements. The users of the
>>   	 * @drm_writeback_connector control the behaviour of the @encoder
>>   	 * by passing the @enc_funcs parameter to drm_writeback_connector_init()
>>   	 * function.
>> +	 *
>> +	 * For some vendor drivers, the hardware resources are shared between
>> +	 * writeback encoder and rest of the display pipeline.
>> +	 * To accommodate such cases, encoder is a handle to the real encoder
>> +	 * hardware.
>> +	 *
>> +	 * For current existing writeback users, this shall continue to be the
>> +	 * embedded encoder for the writeback connector.
>> +	 */
>> +	struct drm_encoder *encoder;
>> +
>> +	/**
>> +	 * @internal_encoder: internal encoder used by writeback when
>> +	 * drm_writeback_connector_init() is used.
>> +	 * @encoder will be assigned to this for those cases
>> +	 *
>> +	 * This will be unused when drm_writeback_connector_init_with_encoder()
>> +	 * is used.
>>   	 */
>> -	struct drm_encoder encoder;
>> +	struct drm_encoder internal_encoder;
>>   
>>   	/**
>>   	 * @pixel_formats_blob_ptr:
>