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From:   Douglas Anderson <dianders@chromium.org>
To:     dri-devel@lists.freedesktop.org, Maxime Ripard <mripard@kernel.org>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Douglas Anderson <dianders@chromium.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@gmail.com>,
        =?UTF-8?q?Guido=20G=C3=BCnther?= <agx@sigxcpu.org>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Ondrej Jirman <megous@megous.com>,
        Purism Kernel Team <kernel@puri.sm>,
        Sam Ravnborg <sam@ravnborg.org>, linux-kernel@vger.kernel.org
Subject: [RFC PATCH 07/10] drm/panel: st7703: Don't store+check prepared
Date:   Fri,  4 Aug 2023 14:06:10 -0700
Message-ID: <20230804140605.RFC.7.Ifc436b262d72f1a33ddef10adfd7578d4acb60d8@changeid>
In-Reply-To: <20230804210644.1862287-1-dianders@chromium.org>
References: <20230804210644.1862287-1-dianders@chromium.org>
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As talked about in commit d2aacaf07395 ("drm/panel: Check for already
prepared/enabled in drm_panel"), we want to remove needless code from
panel drivers that was storing and double-checking the
prepared/enabled state. Even if someone was relying on the
double-check before, that double-check is now in the core and not
needed in individual drivers.

For the st7703 panel driver this is fairly straightforward. Like with
many other panels, we need to use the new drm_panel_helper_shutdown()
function to make sure that remove() and shutdown() don't try to
disable/unprepare a panel that hasn't been prepared/enabled. One thing
that is a little different for st7703 is that it has a special
"allpixelson" debugfs file. When this file is written the driver hacks
a disable/unprepare and then a prepare/enable to try to reset the
panel. This debugfs file didn't appear to be particularly safe to use
even before this patch since it would cause a disabled/unprepared
panel to become prepared/enabled. It is nominally even less safe after
this patch since calling it on a panel that wasn't prepared/enabled
will now likely cause a regulator underflow message. If this matters
to anyone, it could be fixed in a future patch.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/gpu/drm/panel/panel-sitronix-st7703.c | 20 ++-----------------
 1 file changed, 2 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7703.c b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
index 6a3945639535..dde903e803d1 100644
--- a/drivers/gpu/drm/panel/panel-sitronix-st7703.c
+++ b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
@@ -22,6 +22,7 @@
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_modes.h>
 #include <drm/drm_panel.h>
+#include <drm/drm_panel_helper.h>
 
 #define DRV_NAME "panel-sitronix-st7703"
 
@@ -58,7 +59,6 @@ struct st7703 {
 	struct gpio_desc *reset_gpio;
 	struct regulator *vcc;
 	struct regulator *iovcc;
-	bool prepared;
 
 	struct dentry *debugfs;
 	const struct st7703_panel_desc *desc;
@@ -486,13 +486,9 @@ static int st7703_unprepare(struct drm_panel *panel)
 {
 	struct st7703 *ctx = panel_to_st7703(panel);
 
-	if (!ctx->prepared)
-		return 0;
-
 	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
 	regulator_disable(ctx->iovcc);
 	regulator_disable(ctx->vcc);
-	ctx->prepared = false;
 
 	return 0;
 }
@@ -502,9 +498,6 @@ static int st7703_prepare(struct drm_panel *panel)
 	struct st7703 *ctx = panel_to_st7703(panel);
 	int ret;
 
-	if (ctx->prepared)
-		return 0;
-
 	dev_dbg(ctx->dev, "Resetting the panel\n");
 	ret = regulator_enable(ctx->vcc);
 	if (ret < 0) {
@@ -522,8 +515,6 @@ static int st7703_prepare(struct drm_panel *panel)
 	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
 	msleep(20);
 
-	ctx->prepared = true;
-
 	return 0;
 
 disable_vcc:
@@ -665,15 +656,8 @@ static int st7703_probe(struct mipi_dsi_device *dsi)
 static void st7703_shutdown(struct mipi_dsi_device *dsi)
 {
 	struct st7703 *ctx = mipi_dsi_get_drvdata(dsi);
-	int ret;
 
-	ret = drm_panel_unprepare(&ctx->panel);
-	if (ret < 0)
-		dev_err(&dsi->dev, "Failed to unprepare panel: %d\n", ret);
-
-	ret = drm_panel_disable(&ctx->panel);
-	if (ret < 0)
-		dev_err(&dsi->dev, "Failed to disable panel: %d\n", ret);
+	drm_panel_helper_shutdown(&ctx->panel);
 }
 
 static void st7703_remove(struct mipi_dsi_device *dsi)
-- 
2.41.0.585.gd2178a4bd4-goog