mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-09-29 22:02:02 +00:00
Code Issues Releases Wiki Activity

drm/sun4i: tcon: fix inverted DCLK polarity

Browse source 
During commit 88bc417856 ("drm: Use new
DRM_BUS_FLAG_*_(DRIVE|SAMPLE)_(POS|NEG)EDGE flags") DRM_BUS_FLAG_*
macros have been changed to avoid ambiguity but just because of this
ambiguity previous DRM_BUS_FLAG_PIXDATA_(POS/NEG)EDGE were used meaning
_SAMPLE_ not _DRIVE_. This leads to DLCK inversion and need to fix but
instead of swapping phase values, let's adopt an easier approach Maxime
suggested:
It turned out that bit 26 of SUN4I_TCON0_IO_POL_REG is dedicated to
invert DCLK polarity and this makes things really easier than before. So
let's handle DCLK polarity by adding SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE
as bit 26 and activating according to bus_flags the same way it is done
for all the other signals polarity.

Fixes: 88bc417856 ("drm: Use new DRM_BUS_FLAG_*_(DRIVE|SAMPLE)_(POS|NEG)EDGE flags")
Suggested-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20210114081732.9386-1-giulio.benetti@benettiengineering.com
This commit is contained in:
Giulio Benetti 2021-01-14 09:17:32 +01:00 committed by Maxime Ripard
parent 657b65058b
commit 67f4aeb2b4
No known key found for this signature in database
GPG key ID: E3EF0D6F671851C5
2 changed files with 3 additions and 19 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

21
drivers/gpu/drm/sun4i/sun4i_tcon.c
View file

@ -569,30 +569,13 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
if (info->bus_flags & DRM_BUS_FLAG_DE_LOW)
val |= SUN4I_TCON0_IO_POL_DE_NEGATIVE;
/*
* 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.
* Following code is a way to avoid quirks all around TCON
* and DOTCLOCK drivers.
*/
if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_POSEDGE)
clk_set_phase(tcon->dclk, 240);
if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
clk_set_phase(tcon->dclk, 0);
val |= SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE;
regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
SUN4I_TCON0_IO_POL_HSYNC_POSITIVE |
SUN4I_TCON0_IO_POL_VSYNC_POSITIVE |
SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE |
SUN4I_TCON0_IO_POL_DE_NEGATIVE,
val);

1
drivers/gpu/drm/sun4i/sun4i_tcon.h
View file

@ -113,6 +113,7 @@
#define SUN4I_TCON0_IO_POL_REG 0x88
#define SUN4I_TCON0_IO_POL_DCLK_PHASE(phase) ((phase & 3) << 28)
#define SUN4I_TCON0_IO_POL_DE_NEGATIVE BIT(27)
#define SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE BIT(26)
#define SUN4I_TCON0_IO_POL_HSYNC_POSITIVE BIT(25)
#define SUN4I_TCON0_IO_POL_VSYNC_POSITIVE BIT(24)