Re: [Freedreno] [PATCH v6 4/4] drm: allow real encoder to be passed for drm_writeback_connector

[Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>]

Hi Laurent

On 4/5/2022 10:02 AM, Laurent Pinchart wrote:
> Hi Abhinav,
>
> On Tue, Apr 05, 2022 at 09:53:57AM -0700, Abhinav Kumar wrote:
> > On 4/5/2022 9:47 AM, Laurent Pinchart wrote:
> > > On Mon, Apr 04, 2022 at 11:43:37AM -0700, Rob Clark wrote:
> > > > On Fri, Apr 1, 2022 at 8:38 AM Laurent Pinchart wrote:
> > > > > On Thu, Mar 31, 2022 at 05:12:13PM -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.
> > > > > >
> > > > > > changes in v6:
> > > > > >         - assign the encoder inside
> > > > > >           drm_writeback_connector_init_with_encoder() for
> > > > > >           better readability
> > > > > >         - improve some documentation for internal encoder
> > > > > >
> > > > > > Co-developed-by: Kandpal Suraj <suraj.kandpal@xxxxxxxxx>
> > > > > > Signed-off-by: Kandpal Suraj <suraj.kandpal@xxxxxxxxx>
> > > > > > Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> > > > > > ---
> > > > > >    drivers/gpu/drm/drm_writeback.c | 18 ++++++++++++------
> > > > > >    drivers/gpu/drm/vc4/vc4_txp.c   | 14 ++++++++------
> > > > > >    include/drm/drm_writeback.h     | 21 +++++++++++++++++++--
> > > > >
> > > > > Please split this in two patches, one for the DRM core and one for the
> > > > > VC4 driver. This applies to most patches as a general rule, with the
> > > > > main exception being API refactoring that requires changing the
> > > > > implementation and all its users in a single patch.
> > > >
> > > > But this *is* API refactoring ;-)
> > >
> > > Partly at least :-) Looking at the API change itself, wouldn't we
> > > minimize the extra changes to vc4 if we moved this patch before 3/4 ?
> >
> > I can move all the changes done in vc4 except below part to the change
> > 3/4 itself because that way I can show usage of vc4->drm_enc with the
> > new API. Let me know if that works.
>
> What I meant is moving the API refactoring from 4/4 before the current
> 3/4, with minimal changes to vc4 there (only to avoid introducing a
> bisection breakge), and then move most of the vc4 changes from this
> patch to the current 3/4 (which will become 4/4). If that's what you
> meant too, it sounds good to me.

The API refactoring part in this patch is tied closely with changing the 
wb_connector's encoder to a pointer which breaks vc4.

I have not made any additional refactoring changes here.

So I am not sure how to decouple this more.

Thanks

Abhinav


> > The only part which will remain is the below one:
> >
> > @@ -523,7 +525,7 @@  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);
> >
> > Since i dont know vc4 driver very well, I was not sure of a good way to
> > decouple this dependency.
> >
> > Let me know if that works.
> >
> > > > > >    3 files changed, 39 insertions(+), 14 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> > > > > > index 797223c..7f72109 100644
> > > > > > --- a/drivers/gpu/drm/drm_writeback.c
> > > > > > +++ b/drivers/gpu/drm/drm_writeback.c
> > > > > > @@ -179,21 +179,21 @@ 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;
> > > > > >    }
> > > > > > @@ -238,6 +238,12 @@ 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 5e53f02..a9b4f83 100644
> > > > > > --- a/drivers/gpu/drm/vc4/vc4_txp.c
> > > > > > +++ b/drivers/gpu/drm/vc4/vc4_txp.c
> > > > > > @@ -151,6 +151,8 @@ struct vc4_txp {
> > > > > >
> > > > > >         struct platform_device *pdev;
> > > > > >
> > > > > > +     struct drm_encoder drm_enc;
> > > > > > +
> > > > > >         struct drm_writeback_connector connector;
> > > > > >
> > > > > >         void __iomem *regs;
> > > > > > @@ -159,7 +161,7 @@ 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, drm_enc);
> > > > > >    }
> > > > > >
> > > > > >    static inline struct vc4_txp *connector_to_vc4_txp(struct drm_connector *conn)
> > > > > > @@ -499,9 +501,9 @@ static int vc4_txp_bind(struct device *dev, struct device *master, void *data)
> > > > > >
> > > > > >         wb_conn = &txp->connector;
> > > > > >
> > > > > > -     drm_encoder_helper_add(&wb_conn->encoder, &vc4_txp_encoder_helper_funcs);
> > > > > > +     drm_encoder_helper_add(&txp->drm_enc, &vc4_txp_encoder_helper_funcs);
> > > > > >
> > > > > > -     ret = drm_encoder_init(drm, &wb_conn->encoder,
> > > > > > +     ret = drm_encoder_init(drm, &txp->drm_enc,
> > > > > >                         &vc4_txp_encoder_funcs,
> > > > > >                         DRM_MODE_ENCODER_VIRTUAL, NULL);
> > > > > >
> > > > > > @@ -511,10 +513,10 @@ static int vc4_txp_bind(struct device *dev, struct device *master, void *data)
> > > > > >         drm_connector_helper_add(&wb_conn->base,
> > > > > >                                  &vc4_txp_connector_helper_funcs);
> > > > > >
> > > > > > -     ret = drm_writeback_connector_init_with_encoder(drm, wb_conn, &wb_conn->encoder,
> > > > > > +     ret = drm_writeback_connector_init_with_encoder(drm, wb_conn, &txp->drm_enc,
> > > > > >                         &vc4_txp_connector_funcs, drm_fmts, ARRAY_SIZE(drm_fmts));
> > > > > >         if (ret) {
> > > > > > -             drm_encoder_cleanup(&wb_conn->encoder);
> > > > > > +             drm_encoder_cleanup(&txp->drm_enc);
> > > > > >                 return ret;
> > > > > >         }
> > > > > >
> > > > > > @@ -523,7 +525,7 @@ 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 4795024..3f5c330 100644
> > > > > > --- a/include/drm/drm_writeback.h
> > > > > > +++ b/include/drm/drm_writeback.h
> > > > > > @@ -25,15 +25,32 @@ 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;
> > > > > > +     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 internal_encoder;
> > > > > > +     /**
> > > > > >          * @pixel_formats_blob_ptr:
> > > > > >          *
> > > > > >          * DRM blob property data for the pixel formats list on writeback