OpenWrt – Rev 4
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From 7f98947db09ad419ca73082230ade1f29f18bd82 Mon Sep 17 00:00:00 2001
From: Eric Anholt <eric@anholt.net>
Date: Mon, 6 Mar 2017 12:17:16 -0800
Subject: [PATCH 128/454] panel-raspberrypi-touchscreen: Round up clk rate to
fix DSI panel.
Commit 488f9bc8e3def93e0baef53cee2026c2cb0d8956 slightly increased the
reported rate of PLLD, so the clk driver decided that PLLD/3/8 was now
higher than our requested pixel clock rate and rejected it in favor of
PLLD/4/8, which then ran the pixel clock way out of spec.
By bumping the requested clock rate just slightly, we get back to
PLLD/3/8 like we wanted and the panel displays content again.
Signed-off-by: Eric Anholt <eric@anholt.net>
---
drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
+++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
@@ -220,7 +220,12 @@ static const struct drm_display_mode rpi
#define HBP 46
#define HFP ((PIXEL_CLOCK / (VTOTAL * VREFRESH)) - (HACT + HSW + HBP))
- .clock = PIXEL_CLOCK / 1000,
+ /* Round up the pixel clock a bit (10khz), so that the
+ * "don't run things faster than the requested clock
+ * rate" rule of the clk driver doesn't reject the
+ * divide-by-3 mode due to rounding error.
+ */
+ .clock = PIXEL_CLOCK / 1000 + 10,
.hdisplay = HACT,
.hsync_start = HACT + HFP,
.hsync_end = HACT + HFP + HSW,