linux-kernel - Re: [PATCH 2/2] drm/bridge: ps8640: Add a cache for EDID

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Message-ID: <CAN6tsi5YT6Bb85GUn3+Cit=F2doh_up9nqDNQDyMUP9Ttxb09w@mail.gmail.com>
Date:   Tue, 14 Mar 2023 12:21:50 +0100
From:   Robert Foss <rfoss@...nel.org>
To:     Pin-yen Lin <treapking@...omium.org>
Cc:     Douglas Anderson <dianders@...omium.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 2/2] drm/bridge: ps8640: Add a cache for EDID

On Tue, Mar 14, 2023 at 12:01 PM Pin-yen Lin <treapking@...omium.org> wrote:
>
> When there are multiple EDID reads, the bridge will be repeatedly
> enabled and disabled. Add a cache for EDID to speed this up.
>
> Signed-off-by: Pin-yen Lin <treapking@...omium.org>
> ---
>
>  drivers/gpu/drm/bridge/parade-ps8640.c | 61 ++++++++++++++++----------
>  1 file changed, 37 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> index 08de501c436e..4d594be8b89c 100644
> --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> @@ -105,6 +105,7 @@ struct ps8640 {
>         struct gpio_desc *gpio_reset;
>         struct gpio_desc *gpio_powerdown;
>         struct device_link *link;
> +       struct edid *edid;
>         bool pre_enabled;
>         bool need_post_hpd_delay;
>  };
> @@ -543,34 +544,37 @@ static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
>  {
>         struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
>         bool poweroff = !ps_bridge->pre_enabled;
> -       struct edid *edid;
>
> -       /*
> -        * When we end calling get_edid() triggered by an ioctl, i.e
> -        *
> -        *   drm_mode_getconnector (ioctl)
> -        *     -> drm_helper_probe_single_connector_modes
> -        *        -> drm_bridge_connector_get_modes
> -        *           -> ps8640_bridge_get_edid
> -        *
> -        * We need to make sure that what we need is enabled before reading
> -        * EDID, for this chip, we need to do a full poweron, otherwise it will
> -        * fail.
> -        */
> -       if (poweroff)
> -               drm_atomic_bridge_chain_pre_enable(bridge, connector->state->state);
> +       if (!ps_bridge->edid) {
> +               /*
> +                * When we end calling get_edid() triggered by an ioctl, i.e
> +                *
> +                *   drm_mode_getconnector (ioctl)
> +                *     -> drm_helper_probe_single_connector_modes
> +                *        -> drm_bridge_connector_get_modes
> +                *           -> ps8640_bridge_get_edid
> +                *
> +                * We need to make sure that what we need is enabled before
> +                * reading EDID, for this chip, we need to do a full poweron,
> +                * otherwise it will fail.
> +                */
> +               if (poweroff)
> +                       drm_atomic_bridge_chain_pre_enable(bridge,
> +                                                          connector->state->state);
>
> -       edid = drm_get_edid(connector,
> -                           ps_bridge->page[PAGE0_DP_CNTL]->adapter);
> +               ps_bridge->edid = drm_get_edid(connector,
> +                                              ps_bridge->page[PAGE0_DP_CNTL]->adapter);
>
> -       /*
> -        * If we call the get_edid() function without having enabled the chip
> -        * before, return the chip to its original power state.
> -        */
> -       if (poweroff)
> -               drm_atomic_bridge_chain_post_disable(bridge, connector->state->state);
> +               /*
> +                * If we call the get_edid() function without having enabled the
> +                * chip before, return the chip to its original power state.
> +                */
> +               if (poweroff)
> +                       drm_atomic_bridge_chain_post_disable(bridge,
> +                                                            connector->state->state);
> +       }
>
> -       return edid;
> +       return drm_edid_duplicate(ps_bridge->edid);
>  }
>
>  static void ps8640_runtime_disable(void *data)
> @@ -767,6 +771,14 @@ static int ps8640_probe(struct i2c_client *client)
>         return ret;
>  }
>
> +static void ps8640_remove(struct i2c_client *client)
> +{
> +       struct ps8640 *ps_bridge = i2c_get_clientdata(client);
> +
> +       kfree(ps_bridge->edid);
> +       ps_bridge->edid = NULL;
> +}
> +
>  static const struct of_device_id ps8640_match[] = {
>         { .compatible = "parade,ps8640" },
>         { }
> @@ -775,6 +787,7 @@ MODULE_DEVICE_TABLE(of, ps8640_match);
>
>  static struct i2c_driver ps8640_driver = {
>         .probe_new = ps8640_probe,
> +       .remove = ps8640_remove,
>         .driver = {
>                 .name = "ps8640",
>                 .of_match_table = ps8640_match,
> --
> 2.40.0.rc1.284.g88254d51c5-goog
>


Reviewed-by: Robert Foss <rfoss@...nel.org>