linux-kernel - [PATCH] drm/panel-simple: Fix dotclock for Ortustech COM37H3M

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Date:   Tue, 10 Mar 2020 08:43:19 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Ville Syrjala <ville.syrjala@...ux.intel.com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Sam Ravnborg <sam@...nborg.org>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, letux-kernel@...nphoenux.org,
        "H. Nikolaus Schaller" <hns@...delico.com>
Subject: [PATCH] drm/panel-simple: Fix dotclock for Ortustech COM37H3M

The currently listed dotclock disagrees with the currently
listed vrefresh rate. Change the dotclock to match the vrefresh.

There are two variants of the COM37H3M panel.
The older one's COM37H3M05DTC data sheet specifies:

                         MIN      TYP     MAX
CLK frequency    fCLK     --       22.4    26.3 MHz (in VGA mode)
VSYNC Frequency  fVSYNC   54       60      66   Hz
VSYNC cycle time tv       --      650      --   H
HSYNC frequency  fHSYNC   --       39.3    --   kHz
HSYNC cycle time th       --      570      --   CLK

The newer one's COM37H3M99DTC data sheet says:

                         MIN      TYP     MAX
CLK frequency    fCLK     18       19.8    27   MHz
VSYNC Frequency  fVSYNC   54       60      66   Hz
VSYNC cycle time tv      646      650     700   H
HSYNC frequency  fHSYNC  --        39.0    50.0 kHz
HSYNC cycle time th      504      508     630   CLK

So we choose a parameter set that lies within the specs
of both variants. We start at .vrefresh = 60,
choose .htotal = 570 and .vtotal = 650 and end up
in a clock of 22.230 MHz.

Reported-by: Ville Syrjala <ville.syrjala@...ux.intel.com>
Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
---
 drivers/gpu/drm/panel/panel-simple.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index e14c14ac62b5..b4cb23d4898d 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -2390,15 +2390,15 @@ static const struct panel_desc ontat_yx700wv03 = {
 };
 
 static const struct drm_display_mode ortustech_com37h3m_mode  = {
-	.clock = 22153,
+	.clock = 22230,
 	.hdisplay = 480,
-	.hsync_start = 480 + 8,
-	.hsync_end = 480 + 8 + 10,
-	.htotal = 480 + 8 + 10 + 10,
+	.hsync_start = 480 + 40,
+	.hsync_end = 480 + 40 + 10,
+	.htotal = 480 + 40 + 10 + 40,
 	.vdisplay = 640,
 	.vsync_start = 640 + 4,
-	.vsync_end = 640 + 4 + 3,
-	.vtotal = 640 + 4 + 3 + 4,
+	.vsync_end = 640 + 4 + 2,
+	.vtotal = 640 + 4 + 2 + 4,
 	.vrefresh = 60,
 	.flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
 };
-- 
2.23.0