From f0fdcf02095ceedf6bfe4e62fa0bb7ea2d251ebc Mon Sep 17 00:00:00 2001 From: Luca Ceresoli Date: Thu, 26 Feb 2026 17:16:45 +0100 Subject: drm/bridge: ti-sn65dsi83: halve horizontal syncs for dual LVDS output commit d0d727746944096a6681dc6adb5f123fc5aa018d upstream. Dual LVDS output (available on the SN65DSI84) requires HSYNC_PULSE_WIDTH and HORIZONTAL_BACK_PORCH to be divided by two with respect to the values used for single LVDS output. While not clearly stated in the datasheet, this is needed according to the DSI Tuner [0] output. It also makes sense intuitively because in dual LVDS output two pixels at a time are output and so the output clock is half of the pixel clock. Some dual-LVDS panels refuse to show any picture without this fix. Divide by two HORIZONTAL_FRONT_PORCH too, even though this register is used only for test pattern generation which is not currently implemented by this driver. [0] https://www.ti.com/tool/DSI-TUNER Fixes: ceb515ba29ba ("drm/bridge: ti-sn65dsi83: Add TI SN65DSI83 and SN65DSI84 driver") Cc: stable@vger.kernel.org Reviewed-by: Marek Vasut Link: https://patch.msgid.link/20260226-ti-sn65dsi83-dual-lvds-fixes-and-test-pattern-v1-2-2e15f5a9a6a0@bootlin.com Signed-off-by: Luca Ceresoli Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/bridge/ti-sn65dsi83.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'drivers') diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c index 60d3552aac81..43344c2e15b7 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c @@ -474,6 +474,7 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge, struct drm_atomic_state *state) { struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge); + const unsigned int dual_factor = ctx->lvds_dual_link ? 2 : 1; const struct drm_bridge_state *bridge_state; const struct drm_crtc_state *crtc_state; const struct drm_display_mode *mode; @@ -606,18 +607,18 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge, /* 32 + 1 pixel clock to ensure proper operation */ le16val = cpu_to_le16(32 + 1); regmap_bulk_write(ctx->regmap, REG_VID_CHA_SYNC_DELAY_LOW, &le16val, 2); - le16val = cpu_to_le16(mode->hsync_end - mode->hsync_start); + le16val = cpu_to_le16((mode->hsync_end - mode->hsync_start) / dual_factor); regmap_bulk_write(ctx->regmap, REG_VID_CHA_HSYNC_PULSE_WIDTH_LOW, &le16val, 2); le16val = cpu_to_le16(mode->vsync_end - mode->vsync_start); regmap_bulk_write(ctx->regmap, REG_VID_CHA_VSYNC_PULSE_WIDTH_LOW, &le16val, 2); regmap_write(ctx->regmap, REG_VID_CHA_HORIZONTAL_BACK_PORCH, - mode->htotal - mode->hsync_end); + (mode->htotal - mode->hsync_end) / dual_factor); regmap_write(ctx->regmap, REG_VID_CHA_VERTICAL_BACK_PORCH, mode->vtotal - mode->vsync_end); regmap_write(ctx->regmap, REG_VID_CHA_HORIZONTAL_FRONT_PORCH, - mode->hsync_start - mode->hdisplay); + (mode->hsync_start - mode->hdisplay) / dual_factor); regmap_write(ctx->regmap, REG_VID_CHA_VERTICAL_FRONT_PORCH, mode->vsync_start - mode->vdisplay); regmap_write(ctx->regmap, REG_VID_CHA_TEST_PATTERN, 0x00); -- cgit v1.2.3