linux/drivers/gpu
Giulio Benetti 490cda5a3c
drm/sun4i: Handle DRM_BUS_FLAG_PIXDATA_*EDGE checking if panel is used.
Handle both positive and negative dclk polarity,
according to bus_flags, taking care of this:

On A20 and similar SoCs, the only way to achieve Positive Edge
(Rising Edge), is setting dclk clock phase to 2/3(240°).
By default TCON works in Negative Edge(Falling Edge), this is why phase
is set to 0 in that case.
Unfortunately there's no way to logically invert dclk through IO_POL
register.
The only acceptable way to work, triple checked with scope,
is using clock phase set to 0° for Negative Edge and set to 240° for
Positive Edge.
On A33 and similar SoCs there would be a 90° phase option, but it divides
also dclk by 2.
This patch is a way to avoid quirks all around TCON and DOTCLOCK drivers
for using A33 90° phase divided by 2 and consequently increase code
complexity.

Check if panel is used. TCON can also handle VGA DAC, then panel could
be empty.

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180718142357.120998-1-giulio.benetti@micronovasrl.com
2018-07-19 17:01:52 +02:00
..
drm drm/sun4i: Handle DRM_BUS_FLAG_PIXDATA_*EDGE checking if panel is used. 2018-07-19 17:01:52 +02:00
host1x drm for v4.18-rc1 2018-06-06 08:16:33 -07:00
ipu-v3 gpu: ipu-v3: prg: avoid possible array underflow 2018-03-15 17:52:08 +01:00
vga docs: Fix some broken references 2018-06-15 18:10:01 -03:00
Makefile