linux-kernel - [RFC PATCH 01/10] Revert "drm/bridge: tc358762: Split register programming from pre-enable to enable"

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Date:   Mon, 16 Oct 2023 19:53:46 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>
Cc:     Marek Vasut <marex@...x.de>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org
Subject: [RFC PATCH 01/10] Revert "drm/bridge: tc358762: Split register programming from pre-enable to enable"

It has been pointed out (e.g. in [1]) that enable is not the best place
for sending the DSI commands. There are hosts (sunxi) that can not
support sending DSI commands once video stream has enabled.

Also most panel drivers send DSI commands in the prepare() callback
(which maps to drm_bridg_funcs::pre_enable()). Thus the DSIM host should
be fixed to be able to send DSI commands from pre_enable() state.

[1] https://lore.kernel.org/dri-devel/CAPY8ntBrhYAmsraDqJGuTrSL6VjGXBAMVoN7xweV7E4qZv+v3Q@mail.gmail.com/
[2] https://github.com/torvalds/lincux/blob/master/include/drm/drm_mipi_dsi.h#L84-L87

Cc: Marek Vasut <marex@...x.de>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 drivers/gpu/drm/bridge/tc358762.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/bridge/tc358762.c b/drivers/gpu/drm/bridge/tc358762.c
index 46198af9eebb..7b9f05f95fd1 100644
--- a/drivers/gpu/drm/bridge/tc358762.c
+++ b/drivers/gpu/drm/bridge/tc358762.c
@@ -185,17 +185,11 @@ static void tc358762_pre_enable(struct drm_bridge *bridge, struct drm_bridge_sta
 		usleep_range(5000, 10000);
 	}
 
-	ctx->pre_enabled = true;
-}
-
-static void tc358762_enable(struct drm_bridge *bridge, struct drm_bridge_state *state)
-{
-	struct tc358762 *ctx = bridge_to_tc358762(bridge);
-	int ret;
-
 	ret = tc358762_init(ctx);
 	if (ret < 0)
 		dev_err(ctx->dev, "error initializing bridge (%d)\n", ret);
+
+	ctx->pre_enabled = true;
 }
 
 static int tc358762_attach(struct drm_bridge *bridge,
@@ -219,7 +213,6 @@ static void tc358762_bridge_mode_set(struct drm_bridge *bridge,
 static const struct drm_bridge_funcs tc358762_bridge_funcs = {
 	.atomic_post_disable = tc358762_post_disable,
 	.atomic_pre_enable = tc358762_pre_enable,
-	.atomic_enable = tc358762_enable,
 	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
 	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
 	.atomic_reset = drm_atomic_helper_bridge_reset,
-- 
2.42.0