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

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Message-Id: <20210416153909.v4.24.If050957eaa85cf45b10bcf61e6f7fa61c9750ebf@changeid>
Date:   Fri, 16 Apr 2021 15:39:47 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>, Wolfram Sang <wsa@...nel.org>
Cc:     Stephen Boyd <swboyd@...omium.org>, robdclark@...omium.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Stanislav Lisovskiy <stanislav.lisovskiy@...el.com>,
        Steev Klimaszewski <steev@...i.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm@...r.kernel.org, Linus W <linus.walleij@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Thierry Reding <thierry.reding@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 24/27] drm/panel: panel-simple: Cache the EDID as long as we retain power

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@...omium.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;
+
 	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