Re: [PATCH v4 24/27] drm/panel: panel-simple: Cache the EDID as long as we retain power

Bjorn Andersson
2021-04-23T16:12:55Z

On Fri 16 Apr 17:39 CDT 2021, Douglas Anderson wrote:

> It doesn't make sense to go out to the bus and read the EDID over and
> over again. Let's cache it and throw away the cache when we turn power
> off from the panel. Autosuspend means that even if there are several
> calls to read the EDID before we officially turn the power on then we
> should get good use out of this cache.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> (no changes since v1)
>
> drivers/gpu/drm/panel/panel-simple.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index 40382c1be692..5a2953c4ca44 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -189,6 +189,8 @@ struct panel_simple {
> struct gpio_desc *enable_gpio;
> struct gpio_desc *hpd_gpio;
>
> + struct edid *edid;
> +
> struct drm_display_mode override_mode;
>
> enum drm_panel_orientation orientation;
> @@ -345,6 +347,9 @@ static int panel_simple_suspend(struct device *dev)
> regulator_disable(p->supply);
> p->unprepared_time = ktime_get();
>
> + kfree(p->edid);
> + p->edid = NULL;

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

But separate of this, shouldn't the driver have a pm_runtime_disable()
in the remove path to synchronize the autosleep? Or is that not how that
works?

Regards,
Bjorn

> +
> return 0;
> }
>
> @@ -510,15 +515,13 @@ static int panel_simple_get_modes(struct drm_panel *panel,
>
> /* probe EDID if a DDC bus is available */
> if (p->ddc) {
> - struct edid *edid;
> -
> pm_runtime_get_sync(panel->dev);
>
> - edid = drm_get_edid(connector, p->ddc);
> - if (edid) {
> - num += drm_add_edid_modes(connector, edid);
> - kfree(edid);
> - }
> + if (!p->edid)
> + p->edid = drm_get_edid(connector, p->ddc);
> +
> + if (p->edid)
> + num += drm_add_edid_modes(connector, p->edid);
>
> pm_runtime_mark_last_busy(panel->dev);
> pm_runtime_put_autosuspend(panel->dev);
> --
> 2.31.1.368.gbe11c130af-goog
>