linux-kernel - Re: [PATCH v4 05/12] drm/vc4: crtc: Lookup the encoder from the register at boot

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Date:   Fri, 21 May 2021 18:58:06 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>, Eric Anholt <eric@...olt.net>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 05/12] drm/vc4: crtc: Lookup the encoder from the
 register at boot

Hi Maxime

On Fri, 7 May 2021 at 16:05, Maxime Ripard <maxime@...no.tech> wrote:
>
> At boot, we can't rely on the vc4_get_crtc_encoder since we don't have a
> state yet and thus will not be able to figure out which connector is
> attached to our CRTC.
>
> However, we have a muxing bit in the CRTC register we can use to get the
> encoder currently connected to the pixelvalve. We can thus read that
> register, lookup the associated register through the vc4_pv_data
> structure, and then pass it to vc4_crtc_disable so that we can perform
> the proper operations.
>
> Fixes: 875a4d536842 ("drm/vc4: drv: Disable the CRTC at boot time")
> Signed-off-by: Maxime Ripard <maxime@...no.tech>

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

> ---
>  drivers/gpu/drm/vc4/vc4_crtc.c | 38 ++++++++++++++++++++++++++++++----
>  1 file changed, 34 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
> index 36ea684a349b..f715648f89dd 100644
> --- a/drivers/gpu/drm/vc4/vc4_crtc.c
> +++ b/drivers/gpu/drm/vc4/vc4_crtc.c
> @@ -413,11 +413,10 @@ static void require_hvs_enabled(struct drm_device *dev)
>  }
>
>  static int vc4_crtc_disable(struct drm_crtc *crtc,
> +                           struct drm_encoder *encoder,
>                             struct drm_atomic_state *state,
>                             unsigned int channel)
>  {
> -       struct drm_encoder *encoder = vc4_get_crtc_encoder(crtc, state,
> -                                                          drm_atomic_get_old_connector_state);
>         struct vc4_encoder *vc4_encoder = to_vc4_encoder(encoder);
>         struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
>         struct drm_device *dev = crtc->dev;
> @@ -458,10 +457,29 @@ static int vc4_crtc_disable(struct drm_crtc *crtc,
>         return 0;
>  }
>
> +static struct drm_encoder *vc4_crtc_get_encoder_by_type(struct drm_crtc *crtc,
> +                                                       enum vc4_encoder_type type)
> +{
> +       struct drm_encoder *encoder;
> +
> +       drm_for_each_encoder(encoder, crtc->dev) {
> +               struct vc4_encoder *vc4_encoder = to_vc4_encoder(encoder);
> +
> +               if (vc4_encoder->type == type)
> +                       return encoder;
> +       }
> +
> +       return NULL;
> +}
> +
>  int vc4_crtc_disable_at_boot(struct drm_crtc *crtc)
>  {
>         struct drm_device *drm = crtc->dev;
>         struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
> +       enum vc4_encoder_type encoder_type;
> +       const struct vc4_pv_data *pv_data;
> +       struct drm_encoder *encoder;
> +       unsigned encoder_sel;
>         int channel;
>
>         if (!(of_device_is_compatible(vc4_crtc->pdev->dev.of_node,
> @@ -480,7 +498,17 @@ int vc4_crtc_disable_at_boot(struct drm_crtc *crtc)
>         if (channel < 0)
>                 return 0;
>
> -       return vc4_crtc_disable(crtc, NULL, channel);
> +       encoder_sel = VC4_GET_FIELD(CRTC_READ(PV_CONTROL), PV_CONTROL_CLK_SELECT);
> +       if (WARN_ON(encoder_sel != 0))
> +               return 0;
> +
> +       pv_data = vc4_crtc_to_vc4_pv_data(vc4_crtc);
> +       encoder_type = pv_data->encoder_types[encoder_sel];
> +       encoder = vc4_crtc_get_encoder_by_type(crtc, encoder_type);
> +       if (WARN_ON(!encoder))
> +               return 0;
> +
> +       return vc4_crtc_disable(crtc, encoder, NULL, channel);
>  }
>
>  static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
> @@ -489,6 +517,8 @@ 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_device *dev = crtc->dev;
>
>         require_hvs_enabled(dev);
> @@ -496,7 +526,7 @@ static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
>         /* Disable vblank irq handling before crtc is disabled. */
>         drm_crtc_vblank_off(crtc);
>
> -       vc4_crtc_disable(crtc, state, old_vc4_state->assigned_channel);
> +       vc4_crtc_disable(crtc, encoder, state, old_vc4_state->assigned_channel);
>
>         /*
>          * Make sure we issue a vblank event after disabling the CRTC if
> --
> 2.31.1
>