[PATCH 2/2] drm/sun4i: tcon: improve DCLK polarity handling

Giulio Benetti
2021-01-06T19:31:54Z

It turned out(Maxime suggestion) that bit 26 of SUN4I_TCON0_IO_POL_REG is
dedicated to invert DCLK polarity and this makes thing really easier than
before. So let's handle DCLK polarity by adding
SUN4I_TCON0_IO_POL_DCLK_POSITIVE as bit 26 and activating according to
bus_flags the same way is done for all the other signals.

Cc: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
---
drivers/gpu/drm/sun4i/sun4i_tcon.c | 20 +-------------------
drivers/gpu/drm/sun4i/sun4i_tcon.h | 1 +
2 files changed, 2 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 52598bb0fb0b..30171ccd87e5 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -569,26 +569,8 @@ 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, 0);
-
- if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
- clk_set_phase(tcon->dclk, 240);
+ val |= SUN4I_TCON0_IO_POL_DCLK_POSITIVE;

regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
SUN4I_TCON0_IO_POL_HSYNC_POSITIVE |
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h
index cfbf4e6c1679..0ce71d10a31b 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.h
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h
@@ -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_POSITIVE BIT(26)
#define SUN4I_TCON0_IO_POL_HSYNC_POSITIVE BIT(25)
#define SUN4I_TCON0_IO_POL_VSYNC_POSITIVE BIT(24)

--
2.25.1