linux-kernel - Re: [PATCH v2 2/4] drm/bridge: use atomic enable/disable for bridge callbacks

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Message-ID: <CAE-0n53a5akPXSJjkD4SvnparcxBpN2LaGt_7J=6petTPukHeQ@mail.gmail.com>
Date:   Tue, 22 Feb 2022 21:19:50 +0000
From:   Stephen Boyd <swboyd@...omium.org>
To:     Vinod Polimera <quic_vpolimer@...cinc.com>, agross@...nel.org,
        airlied@...ux.ie, bjorn.andersson@...aro.org, daniel@...ll.ch,
        devicetree@...r.kernel.org, dianders@...omium.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        krzysztof.kozlowski@...onical.com, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, robdclark@...il.com,
        robh+dt@...nel.org, sam@...nborg.org, seanpaul@...omium.org,
        thierry.reding@...il.com
Cc:     quic_kalyant@...cinc.com, quic_sbillaka@...cinc.com,
        quic_vproddut@...cinc.com
Subject: Re: [PATCH v2 2/4] drm/bridge: use atomic enable/disable for bridge callbacks

Quoting Vinod Polimera (2022-02-21 06:51:24)
> diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
> index b32295a..5c7dc82 100644
> --- a/drivers/gpu/drm/bridge/panel.c
> +++ b/drivers/gpu/drm/bridge/panel.c
> @@ -102,30 +136,82 @@ static void panel_bridge_detach(struct drm_bridge *bridge)
>                 drm_connector_cleanup(connector);
>  }
>
> -static void panel_bridge_pre_enable(struct drm_bridge *bridge)
> +static void panel_bridge_pre_enable(struct drm_bridge *bridge,
> +               struct drm_bridge_state *old_bridge_state)
>  {
>         struct panel_bridge *panel_bridge = drm_bridge_to_panel_bridge(bridge);
> +       struct drm_atomic_state *old_state = old_bridge_state->base.state;
> +       struct drm_encoder *encoder = bridge->encoder;
> +       struct drm_crtc *crtc;
> +       struct drm_crtc_state *old_crtc_state;
> +
> +       crtc = bridge_drm_get_new_connector_crtc(encoder, old_state);
> +       if (!crtc)
> +               return;
> +
> +       old_crtc_state = drm_atomic_get_old_crtc_state(old_state, crtc);
> +       if (old_crtc_state && old_crtc_state->self_refresh_active)

Can you please add some comment about why self_refresh_active means we
should bail out from this function? Such a comment would be helpful to
understand the code quickly vs. having to figure out what the intention
of the logic is. The analogix driver has

/* Don't touch the panel if we're coming back from PSR */

so even mentioning PSR here would be helpful.