linux-kernel - [PATCH] drm/bridge: nwl-dsi: Use vsync/hsync polarity from display mode

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Message-Id: <20240814-nwl-dsi-sync-polarity-v1-1-ee198e369196@geanix.com>
Date: Wed, 14 Aug 2024 12:37:26 +0200
From: Esben Haabendal <esben@...nix.com>
To: 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>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Esben Haabendal <esben@...nix.com>
Subject: [PATCH] drm/bridge: nwl-dsi: Use vsync/hsync polarity from display
 mode

Using the correct bit helps. The documentation specifies bit 0 in both
registers to be controlling polarity of dpi_vsync_input and
dpi_hsync_input polarity. Bit 1 is reserved, and should therefore not be
set.

Tested with panel that requires active high vsync and hsync.

Signed-off-by: Esben Haabendal <esben@...nix.com>
---
 drivers/gpu/drm/bridge/nwl-dsi.c | 8 ++++----
 drivers/gpu/drm/bridge/nwl-dsi.h | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/nwl-dsi.c b/drivers/gpu/drm/bridge/nwl-dsi.c
index 8d54091ec66e..5f05647a3bea 100644
--- a/drivers/gpu/drm/bridge/nwl-dsi.c
+++ b/drivers/gpu/drm/bridge/nwl-dsi.c
@@ -289,13 +289,13 @@ static int nwl_dsi_config_dpi(struct nwl_dsi *dsi)
 
 	nwl_dsi_write(dsi, NWL_DSI_INTERFACE_COLOR_CODING, NWL_DSI_DPI_24_BIT);
 	nwl_dsi_write(dsi, NWL_DSI_PIXEL_FORMAT, color_format);
-	/*
-	 * Adjusting input polarity based on the video mode results in
-	 * a black screen so always pick active low:
-	 */
 	nwl_dsi_write(dsi, NWL_DSI_VSYNC_POLARITY,
+		      dsi->mode.flags & DRM_MODE_FLAG_PVSYNC ?
+		      NWL_DSI_VSYNC_POLARITY_ACTIVE_HIGH :
 		      NWL_DSI_VSYNC_POLARITY_ACTIVE_LOW);
 	nwl_dsi_write(dsi, NWL_DSI_HSYNC_POLARITY,
+		      dsi->mode.flags & DRM_MODE_FLAG_PHSYNC ?
+		      NWL_DSI_HSYNC_POLARITY_ACTIVE_HIGH :
 		      NWL_DSI_HSYNC_POLARITY_ACTIVE_LOW);
 
 	burst_mode = (dsi->dsi_mode_flags & MIPI_DSI_MODE_VIDEO_BURST) &&
diff --git a/drivers/gpu/drm/bridge/nwl-dsi.h b/drivers/gpu/drm/bridge/nwl-dsi.h
index a247a8a11c7c..61e7d65cb1eb 100644
--- a/drivers/gpu/drm/bridge/nwl-dsi.h
+++ b/drivers/gpu/drm/bridge/nwl-dsi.h
@@ -30,11 +30,11 @@
 #define NWL_DSI_PIXEL_FORMAT			0x20c
 #define NWL_DSI_VSYNC_POLARITY			0x210
 #define NWL_DSI_VSYNC_POLARITY_ACTIVE_LOW	0
-#define NWL_DSI_VSYNC_POLARITY_ACTIVE_HIGH	BIT(1)
+#define NWL_DSI_VSYNC_POLARITY_ACTIVE_HIGH	BIT(0)
 
 #define NWL_DSI_HSYNC_POLARITY			0x214
 #define NWL_DSI_HSYNC_POLARITY_ACTIVE_LOW	0
-#define NWL_DSI_HSYNC_POLARITY_ACTIVE_HIGH	BIT(1)
+#define NWL_DSI_HSYNC_POLARITY_ACTIVE_HIGH	BIT(0)
 
 #define NWL_DSI_VIDEO_MODE			0x218
 #define NWL_DSI_HFP				0x21c

---
base-commit: 7c626ce4bae1ac14f60076d00eafe71af30450ba
change-id: 20240814-nwl-dsi-sync-polarity-ddc58435a4c4

Best regards,
-- 
Esben Haabendal <esben@...nix.com>