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drm/sun4i: Handle DRM_BUS_FLAG_PIXDATA_*EDGE 

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.

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/1520963677-124239-1-git-send-email-giulio.benetti@micronovasrl.com
This commit is contained in:
Giulio Benetti 2018-03-13 18:54:37 +01:00 committed by Maxime Ripard
parent e4e4b7ad50
commit 2c17a4368a
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GPG Key ID: D2B4C094214DAF74
1 changed files with 25 additions and 0 deletions
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25
drivers/gpu/drm/sun4i/sun4i_tcon.c
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@ -17,6 +17,7 @@
#include <drm/drm_encoder.h>
#include <drm/drm_modes.h>
#include <drm/drm_of.h>
#include <drm/drm_panel.h>
#include <uapi/drm/drm_mode.h>
@ -343,6 +344,9 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
const struct drm_display_mode *mode)
{
struct drm_panel *panel = tcon->panel;
struct drm_connector *connector = panel->connector;
struct drm_display_info display_info = connector->display_info;
unsigned int bp, hsync, vsync;
u8 clk_delay;
u32 val = 0;
@ -400,6 +404,27 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
if (mode->flags & DRM_MODE_FLAG_PVSYNC)
val |= SUN4I_TCON0_IO_POL_VSYNC_POSITIVE;
/*
* 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 (display_info.bus_flags & DRM_BUS_FLAG_PIXDATA_POSEDGE)
clk_set_phase(tcon->dclk, 240);
if (display_info.bus_flags & DRM_BUS_FLAG_PIXDATA_NEGEDGE)
clk_set_phase(tcon->dclk, 0);
regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
SUN4I_TCON0_IO_POL_HSYNC_POSITIVE | SUN4I_TCON0_IO_POL_VSYNC_POSITIVE,
val);