From 405cacc947f7b58969b2a8ab1568c2d98b245308 Mon Sep 17 00:00:00 2001
From: Hans de Goede <j.w.r.degoede@gmail.com>
Date: Wed, 20 Dec 2017 11:50:17 +0100
Subject: [PATCH] drm/i915/vlv: Add cdclk workaround for DSI
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Git-commit: 405cacc947f7b58969b2a8ab1568c2d98b245308
Patch-mainline: v4.16-rc2
No-fix: c8dae55a8ced625038d52d26e48273707fab2688
References: FATE#322643 bsc#1055900
At least on the Chuwi Vi8 (non pro/plus) the LCD panel will show an image
shifted aprox. 20% to the left (with wraparound) and sometimes also wrong
colors, showing that the panel controller is starting with sampling the
datastream somewhere mid-line. This happens after the first blanking and
re-init of the panel.
After looking at drm.debug output I noticed that initially we inherit the
cdclk of 333333 KHz set by the GOP, but after the re-init we picked 266667
KHz, which turns out to be the cause of this problem, a quick hack to hard
code the cdclk to 333333 KHz makes the problem go away.
I've tested this on various Bay Trail devices, to make sure this not does
cause regressions on other devices and the higher cdclk does not cause
any problems on the following devices:
-GP-electronic T701 1024x600 333333 KHz cdclk after this patch
-PEAQ C1010 1920x1200 333333 KHz cdclk after this patch
-PoV mobii-wintab-800w 800x1280 333333 KHz cdclk after this patch
-Asus Transformer-T100TA 1368x768 320000 KHz cdclk after this patch
Also interesting wrt this is the comment in vlv_calc_cdclk about the
existing workaround to avoid 200 Mhz as clock because that causes issues
in some cases.
This commit extends the "do not use 200 Mhz" workaround with an extra
check to require atleast 320000 KHz (avoiding 266667 KHz) when a DSI
panel is active.
Changes in v2:
-Change the commit message and the code comment to not treat the GOP as
a reference, the GOP should not be treated as a reference
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171220105017.11259-1-hdegoede@redhat.com
(cherry picked from commit c8dae55a8ced625038d52d26e48273707fab2688)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/intel_cdclk.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/drivers/gpu/drm/i915/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/intel_cdclk.c
@@ -1952,6 +1952,14 @@ int intel_crtc_compute_min_cdclk(const s
if (crtc_state->has_audio && INTEL_GEN(dev_priv) >= 9)
min_cdclk = max(2 * 96000, min_cdclk);
+ /*
+ * On Valleyview some DSI panels lose (v|h)sync when the clock is lower
+ * than 320000KHz.
+ */
+ if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DSI) &&
+ IS_VALLEYVIEW(dev_priv))
+ min_cdclk = max(320000, min_cdclk);
+
if (min_cdclk > dev_priv->max_cdclk_freq) {
DRM_DEBUG_KMS("required cdclk (%d kHz) exceeds max (%d kHz)\n",
min_cdclk, dev_priv->max_cdclk_freq);