Channel 1 has polarity bits for vsync and hsync signals but driver never sets them. It turns out that with pre-HDMI2 controllers seemingly there is no issue if polarity is not set. However, with HDMI2 controllers (H6) there often comes to de-synchronization due to phase shift. This causes flickering screen. It's safe to assume that similar issues might happen also with pre-HDMI2 controllers.
Solve issue with setting vsync and hsync polarity. Note that display stacks with tcon top have polarity bits actually in tcon0 polarity register.
Fixes: 9026e0d122ac ("drm: Add Allwinner A10 Display Engine support") Tested-by: Andre Heider a.heider@gmail.com Signed-off-by: Jernej Skrabec jernej.skrabec@siol.net --- drivers/gpu/drm/sun4i/sun4i_tcon.c | 24 ++++++++++++++++++++++++ drivers/gpu/drm/sun4i/sun4i_tcon.h | 5 +++++ 2 files changed, 29 insertions(+)
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c index 6b9af4c08cd6..0d132dae58c0 100644 --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c @@ -672,6 +672,29 @@ static void sun4i_tcon1_mode_set(struct sun4i_tcon *tcon, SUN4I_TCON1_BASIC5_V_SYNC(vsync) | SUN4I_TCON1_BASIC5_H_SYNC(hsync));
+ /* Setup the polarity of sync signals */ + if (tcon->quirks->polarity_in_ch0) { + val = 0; + + if (mode->flags & DRM_MODE_FLAG_PHSYNC) + val |= SUN4I_TCON0_IO_POL_HSYNC_POSITIVE; + + if (mode->flags & DRM_MODE_FLAG_PVSYNC) + val |= SUN4I_TCON0_IO_POL_VSYNC_POSITIVE; + + regmap_write(tcon->regs, SUN4I_TCON0_IO_POL_REG, val); + } else { + val = SUN4I_TCON1_IO_POL_UNKNOWN; + + if (mode->flags & DRM_MODE_FLAG_PHSYNC) + val |= SUN4I_TCON1_IO_POL_HSYNC_POSITIVE; + + if (mode->flags & DRM_MODE_FLAG_PVSYNC) + val |= SUN4I_TCON1_IO_POL_VSYNC_POSITIVE; + + regmap_write(tcon->regs, SUN4I_TCON1_IO_POL_REG, val); + } + /* Map output pins to channel 1 */ regmap_update_bits(tcon->regs, SUN4I_TCON_GCTL_REG, SUN4I_TCON_GCTL_IOMAP_MASK, @@ -1500,6 +1523,7 @@ static const struct sun4i_tcon_quirks sun8i_a83t_tv_quirks = {
static const struct sun4i_tcon_quirks sun8i_r40_tv_quirks = { .has_channel_1 = true, + .polarity_in_ch0 = true, .set_mux = sun8i_r40_tcon_tv_set_mux, };
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h index c5ac1b02482c..b504fb2d3de5 100644 --- a/drivers/gpu/drm/sun4i/sun4i_tcon.h +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h @@ -154,6 +154,10 @@ #define SUN4I_TCON1_BASIC5_V_SYNC(height) (((height) - 1) & 0x3ff)
#define SUN4I_TCON1_IO_POL_REG 0xf0 +#define SUN4I_TCON1_IO_POL_UNKNOWN BIT(26) +#define SUN4I_TCON1_IO_POL_HSYNC_POSITIVE BIT(25) +#define SUN4I_TCON1_IO_POL_VSYNC_POSITIVE BIT(24) + #define SUN4I_TCON1_IO_TRI_REG 0xf4
#define SUN4I_TCON_ECC_FIFO_REG 0xf8 @@ -236,6 +240,7 @@ struct sun4i_tcon_quirks { bool needs_de_be_mux; /* sun6i needs mux to select backend */ bool needs_edp_reset; /* a80 edp reset needed for tcon0 access */ bool supports_lvds; /* Does the TCON support an LVDS output? */ + bool polarity_in_ch0; /* some tcon1 channels have polarity bits in tcon0 pol register */ u8 dclk_min_div; /* minimum divider for TCON0 DCLK */
/* callback to handle tcon muxing options */