Re: [PATCH v8 05/10] drm/vc4: crtc: Rework the encoder retrieval code (again)

From: Dave Stevenson <dave.stevenson@raspberrypi.com>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>,
	Tim Gover <tim.gover@raspberrypi.com>,
	Emma Anholt <emma@anholt.net>, David Airlie <airlied@linux.ie>,
	LKML <linux-kernel@vger.kernel.org>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	bcm-kernel-feedback-list@broadcom.com,
	linux-rpi-kernel@lists.infradead.org,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Daniel Vetter <daniel.vetter@intel.com>,
	Phil Elwell <phil@raspberrypi.com>,
	Dom Cobley <dom@raspberrypi.com>
Subject: Re: [PATCH v8 05/10] drm/vc4: crtc: Rework the encoder retrieval code (again)
Date: Tue, 2 Nov 2021 16:32:37 +0000	[thread overview]
Message-ID: <CAPY8ntDHdaz0r8Uxq-QsNkmBSz7Ywbf829uLTj=ZL_OwBhwAgA@mail.gmail.com> (raw)
In-Reply-To: <20211025152903.1088803-6-maxime@cerno.tech>

On Mon, 25 Oct 2021 at 16:29, Maxime Ripard <maxime@cerno.tech> wrote:
>
> It turns out the encoder retrieval code, in addition to being
> unnecessarily complicated, has a bug when only the planes and crtcs are
> affected by a given atomic commit.
>
> Indeed, in such a case, either drm_atomic_get_old_connector_state or
> drm_atomic_get_new_connector_state will return NULL and thus our encoder
> retrieval code will not match on anything.
>
> We can however simplify the code by using drm_for_each_encoder_mask, the
> drm_crtc_state storing the encoders a given CRTC is connected to
> directly and without relying on any other state.
>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>

Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

> ---
>  drivers/gpu/drm/vc4/vc4_crtc.c | 30 +++++++++---------------------
>  drivers/gpu/drm/vc4/vc4_drv.h  |  4 +---
>  2 files changed, 10 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
> index e5c2e29a6f01..fbc1d4638650 100644
> --- a/drivers/gpu/drm/vc4/vc4_crtc.c
> +++ b/drivers/gpu/drm/vc4/vc4_crtc.c
> @@ -282,26 +282,14 @@ static u32 vc4_crtc_get_fifo_full_level_bits(struct vc4_crtc *vc4_crtc,
>   * same CRTC.
>   */
>  struct drm_encoder *vc4_get_crtc_encoder(struct drm_crtc *crtc,
> -                                        struct drm_atomic_state *state,
> -                                        struct drm_connector_state *(*get_state)(struct drm_atomic_state *state,
> -                                                                                 struct drm_connector *connector))
> +                                        struct drm_crtc_state *state)
>  {
> -       struct drm_connector *connector;
> -       struct drm_connector_list_iter conn_iter;
> +       struct drm_encoder *encoder;
>
> -       drm_connector_list_iter_begin(crtc->dev, &conn_iter);
> -       drm_for_each_connector_iter(connector, &conn_iter) {
> -               struct drm_connector_state *conn_state = get_state(state, connector);
> +       WARN_ON(hweight32(state->encoder_mask) > 1);
>
> -               if (!conn_state)
> -                       continue;
> -
> -               if (conn_state->crtc == crtc) {
> -                       drm_connector_list_iter_end(&conn_iter);
> -                       return connector->encoder;
> -               }
> -       }
> -       drm_connector_list_iter_end(&conn_iter);
> +       drm_for_each_encoder_mask(encoder, crtc->dev, state->encoder_mask)
> +               return encoder;
>
>         return NULL;
>  }
> @@ -550,8 +538,7 @@ static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
>         struct drm_crtc_state *old_state = drm_atomic_get_old_crtc_state(state,
>                                                                          crtc);
>         struct vc4_crtc_state *old_vc4_state = to_vc4_crtc_state(old_state);
> -       struct drm_encoder *encoder = vc4_get_crtc_encoder(crtc, state,
> -                                                          drm_atomic_get_old_connector_state);
> +       struct drm_encoder *encoder = vc4_get_crtc_encoder(crtc, old_state);
>         struct drm_device *dev = crtc->dev;
>
>         require_hvs_enabled(dev);
> @@ -578,10 +565,11 @@ static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
>  static void vc4_crtc_atomic_enable(struct drm_crtc *crtc,
>                                    struct drm_atomic_state *state)
>  {
> +       struct drm_crtc_state *new_state = drm_atomic_get_new_crtc_state(state,
> +                                                                        crtc);
>         struct drm_device *dev = crtc->dev;
>         struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
> -       struct drm_encoder *encoder = vc4_get_crtc_encoder(crtc, state,
> -                                                          drm_atomic_get_new_connector_state);
> +       struct drm_encoder *encoder = vc4_get_crtc_encoder(crtc, new_state);
>         struct vc4_encoder *vc4_encoder = to_vc4_encoder(encoder);
>
>         require_hvs_enabled(dev);
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
> index f5e678491502..60826aca9e5b 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.h
> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
> @@ -545,9 +545,7 @@ vc4_crtc_to_vc4_pv_data(const struct vc4_crtc *crtc)
>  }
>
>  struct drm_encoder *vc4_get_crtc_encoder(struct drm_crtc *crtc,
> -                                        struct drm_atomic_state *state,
> -                                        struct drm_connector_state *(*get_state)(struct drm_atomic_state *state,
> -                                                                                 struct drm_connector *connector));
> +                                        struct drm_crtc_state *state);
>
>  struct vc4_crtc_state {
>         struct drm_crtc_state base;
> --
> 2.31.1
>