Dithering is supported on TCON channel 0 which is used for LCD panels.
Signed-off-by: Jonathan Liu <net147@xxxxxxxxx>
---
drivers/gpu/drm/sun4i/sun4i_tcon.c | 37 +++++++++++++++++++++++++++++++++++++
drivers/gpu/drm/sun4i/sun4i_tcon.h | 18 +++++++++++++++++-
2 files changed, 54 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 68751b999877..cf313ca858b3 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -12,11 +12,13 @@
#include <drm/drmP.h>
#include <drm/drm_atomic_helper.h>
+#include <drm/drm_connector.h>
#include <drm/drm_crtc.h>
#include <drm/drm_crtc_helper.h>
#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>
@@ -168,7 +170,9 @@ void sun4i_tcon0_mode_set(struct sun4i_tcon *tcon,
struct drm_display_mode *mode)
{
unsigned int bp, hsync, vsync;
+ u32 bus_format = 0;
u8 clk_delay;
+ struct drm_connector *connector = tcon->panel->connector;
u32 val = 0;
/* Configure the dot clock */
@@ -230,6 +234,39 @@ void sun4i_tcon0_mode_set(struct sun4i_tcon *tcon,
SUN4I_TCON0_IO_POL_HSYNC_POSITIVE | SUN4I_TCON0_IO_POL_VSYNC_POSITIVE,
val);
+ if (connector->display_info.num_bus_formats)
+ bus_format = connector->display_info.bus_formats[0];
+
+ switch (bus_format) {
+ case MEDIA_BUS_FMT_RGB565_1X16:
+ case MEDIA_BUS_FMT_RGB666_1X18:
+ /* Enable dithering */
+ /* FIXME: Undocumented bits */
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_SEED0_REG, 0x11111111);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_SEED1_REG, 0x11111111);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_SEED2_REG, 0x11111111);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_SEED3_REG, 0x11111111);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_SEED4_REG, 0x11111111);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_SEED5_REG, 0x11111111);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_TAB0_REG, 0x01010000);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_TAB1_REG, 0x15151111);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_TAB2_REG, 0x57575555);
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_TAB3_REG, 0x7f7f7777);
+ val = SUN4I_TCON0_FRM_CTL_ENABLE;
+
+ if (bus_format == MEDIA_BUS_FMT_RGB565_1X16) {
+ val |= SUN4I_TCON0_FRM_CTL_MODE_R;
+ val |= SUN4I_TCON0_FRM_CTL_MODE_B;
+ }
+
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_CTL_REG, val);
+ break;
+ default:
+ /* Disable dithering */
+ regmap_write(tcon->regs, SUN4I_TCON0_FRM_CTL_REG, 0);
+ break;
+ }
+
/* Map output pins to channel 0 */
regmap_update_bits(tcon->regs, SUN4I_TCON_GCTL_REG,
SUN4I_TCON_GCTL_IOMAP_MASK,
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h
index d9e1357cc8ae..d64d45144c91 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.h
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h
@@ -31,7 +31,23 @@
#define SUN4I_TCON_GINT0_VBLANK_INT(pipe) BIT(15 - (pipe))
#define SUN4I_TCON_GINT1_REG 0x8
-#define SUN4I_TCON_FRM_CTL_REG 0x10
+
+#define SUN4I_TCON0_FRM_CTL_REG 0x10
+#define SUN4I_TCON0_FRM_CTL_ENABLE BIT(31)
+#define SUN4I_TCON0_FRM_CTL_MODE_R BIT(6)
+#define SUN4I_TCON0_FRM_CTL_MODE_G BIT(5)
+#define SUN4I_TCON0_FRM_CTL_MODE_B BIT(4)
+
+#define SUN4I_TCON0_FRM_SEED0_REG 0x14
+#define SUN4I_TCON0_FRM_SEED1_REG 0x18
+#define SUN4I_TCON0_FRM_SEED2_REG 0x1c
+#define SUN4I_TCON0_FRM_SEED3_REG 0x20
+#define SUN4I_TCON0_FRM_SEED4_REG 0x24
+#define SUN4I_TCON0_FRM_SEED5_REG 0x28
+#define SUN4I_TCON0_FRM_TAB0_REG 0x2c
+#define SUN4I_TCON0_FRM_TAB1_REG 0x30
+#define SUN4I_TCON0_FRM_TAB2_REG 0x34
+#define SUN4I_TCON0_FRM_TAB3_REG 0x38
#define SUN4I_TCON0_CTL_REG 0x40
#define SUN4I_TCON0_CTL_TCON_ENABLE BIT(31)
--
2.14.2
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