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Subject[PATCH 5.4 26/78] drm/sun4i: tcon: Set RGB DCLK min. divider based on hardware model
Date
From: Chen-Yu Tsai <wens@csie.org>

commit 4396393fb96449c56423fb4b351f76e45a6bcaf6 upstream.

In commit 0b8e7bbde5e7 ("drm/sun4i: tcon: Set min division of TCON0_DCLK
to 1.") it was assumed that all TCON variants support a minimum divider
of 1 if only DCLK was used.

However, the oldest generation of hardware only supports minimum divider
of 4 if only DCLK is used. If a divider of 1 was used on this old
hardware, some scrolling artifact would appear. A divider of 2 seemed
OK, but a divider of 3 had artifacts as well.

Set the minimum divider when outputing to parallel RGB based on the
hardware model, with a minimum of 4 for the oldest (A10/A10s/A13/A20)
hardware, and a minimum of 1 for the rest. A value is not set for the
TCON variants lacking channel 0.

This fixes the scrolling artifacts seen on my A13 tablet.

Fixes: 0b8e7bbde5e7 ("drm/sun4i: tcon: Set min division of TCON0_DCLK to 1.")
Cc: <stable@vger.kernel.org> # 5.4.x
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200107070113.28951-1-wens@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/sun4i/sun4i_tcon.c | 15 ++++++++++++---
drivers/gpu/drm/sun4i/sun4i_tcon.h | 1 +
2 files changed, 13 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -488,7 +488,7 @@ static void sun4i_tcon0_mode_set_rgb(str

WARN_ON(!tcon->quirks->has_channel_0);

- tcon->dclk_min_div = 1;
+ tcon->dclk_min_div = tcon->quirks->dclk_min_div;
tcon->dclk_max_div = 127;
sun4i_tcon0_mode_set_common(tcon, mode);

@@ -1425,12 +1425,14 @@ static int sun8i_r40_tcon_tv_set_mux(str
static const struct sun4i_tcon_quirks sun4i_a10_quirks = {
.has_channel_0 = true,
.has_channel_1 = true,
+ .dclk_min_div = 4,
.set_mux = sun4i_a10_tcon_set_mux,
};

static const struct sun4i_tcon_quirks sun5i_a13_quirks = {
.has_channel_0 = true,
.has_channel_1 = true,
+ .dclk_min_div = 4,
.set_mux = sun5i_a13_tcon_set_mux,
};

@@ -1439,6 +1441,7 @@ static const struct sun4i_tcon_quirks su
.has_channel_1 = true,
.has_lvds_alt = true,
.needs_de_be_mux = true,
+ .dclk_min_div = 1,
.set_mux = sun6i_tcon_set_mux,
};

@@ -1446,11 +1449,13 @@ static const struct sun4i_tcon_quirks su
.has_channel_0 = true,
.has_channel_1 = true,
.needs_de_be_mux = true,
+ .dclk_min_div = 1,
};

static const struct sun4i_tcon_quirks sun7i_a20_quirks = {
.has_channel_0 = true,
.has_channel_1 = true,
+ .dclk_min_div = 4,
/* Same display pipeline structure as A10 */
.set_mux = sun4i_a10_tcon_set_mux,
};
@@ -1458,11 +1463,13 @@ static const struct sun4i_tcon_quirks su
static const struct sun4i_tcon_quirks sun8i_a33_quirks = {
.has_channel_0 = true,
.has_lvds_alt = true,
+ .dclk_min_div = 1,
};

static const struct sun4i_tcon_quirks sun8i_a83t_lcd_quirks = {
.supports_lvds = true,
.has_channel_0 = true,
+ .dclk_min_div = 1,
};

static const struct sun4i_tcon_quirks sun8i_a83t_tv_quirks = {
@@ -1476,11 +1483,13 @@ static const struct sun4i_tcon_quirks su

static const struct sun4i_tcon_quirks sun8i_v3s_quirks = {
.has_channel_0 = true,
+ .dclk_min_div = 1,
};

static const struct sun4i_tcon_quirks sun9i_a80_tcon_lcd_quirks = {
- .has_channel_0 = true,
- .needs_edp_reset = true,
+ .has_channel_0 = true,
+ .needs_edp_reset = true,
+ .dclk_min_div = 1,
};

static const struct sun4i_tcon_quirks sun9i_a80_tcon_tv_quirks = {
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.h
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h
@@ -224,6 +224,7 @@ 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? */
+ u8 dclk_min_div; /* minimum divider for TCON0 DCLK */

/* callback to handle tcon muxing options */
int (*set_mux)(struct sun4i_tcon *, const struct drm_encoder *);

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