[U-Boot] [PATCH v2] sunxi: video: Force h/vsync active high when using ext. vga dac on some boards

Hans de Goede
2015-01-28T10:47:21Z

On both my A13-OLinuxIno and my A13-OLinuxIno-Micro, the vga output gives an
unstable image when active low v or hsync is used.

The problem seems to be specific to the OLinuxIno A13 (normal & micro)
boards. I've just looked up the schematics and they use an opendrain driver
for the vga sync lines, and with sync pulses it is the logical high->low
edge of the pulse which counts for the timing, which with an active low
sync is being driven by the pull-up, and that simply seems to not drive
it hard enough to get a stable image.

So force v and hsync active high on these boards. independent of what the
modeline says. This fixes the unstable image.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
board/sunxi/Kconfig | 10 ++++++++++
configs/A13-OLinuXinoM_defconfig | 1 +
configs/A13-OLinuXino_defconfig | 1 +
drivers/video/sunxi_display.c | 12 +++++++++---
4 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig
index 8b94311..ab884dc 100644
--- a/board/sunxi/Kconfig
+++ b/board/sunxi/Kconfig
@@ -190,6 +190,16 @@ config VIDEO_VGA_VIA_LCD
LCD interface driving a VGA connector, such as found on the
Olimex A13 boards.

+config VIDEO_VGA_VIA_LCD_FORCE_SYNC_ACTIVE_HIGH
+ boolean "Force sync active high for VGA via LCD controller support"
+ depends on VIDEO_VGA_VIA_LCD
+ default n
+ ---help---
+ Say Y here if you've a board which uses opendrain drivers for the vga
+ hsync and vsync signals. Opendrain drivers cannot generate steep enough
+ positive edges for a stable video output, so on boards with opendrain
+ drivers the sync signals must always be active high.
+
config VIDEO_VGA_EXTERNAL_DAC_EN
string "LCD panel power enable pin"
depends on VIDEO_VGA_VIA_LCD
diff --git a/configs/A13-OLinuXinoM_defconfig b/configs/A13-OLinuXinoM_defconfig
index 1c3fc3a..a04f2b3 100644
--- a/configs/A13-OLinuXinoM_defconfig
+++ b/configs/A13-OLinuXinoM_defconfig
@@ -4,6 +4,7 @@ CONFIG_FDTFILE="sun5i-a13-olinuxino-micro.dtb"
CONFIG_USB1_VBUS_PIN="PG11"
CONFIG_VIDEO_HDMI=n
CONFIG_VIDEO_VGA_VIA_LCD=y
+CONFIG_VIDEO_VGA_VIA_LCD_FORCE_SYNC_ACTIVE_HIGH=y
# For use with the Olimex 7" LCD module, adjust timings for other displays
# Set video-mode=sunxi:800x600-24 at 60,monitor=lcd in the env. to enable
CONFIG_VIDEO_LCD_MODE="x:800,y:480,depth:18,pclk_khz:33000,le:16,ri:209,up:22,lo:22,hs:30,vs:1,sync:3,vmode:0"
diff --git a/configs/A13-OLinuXino_defconfig b/configs/A13-OLinuXino_defconfig
index 0daaaae..806d5b7 100644
--- a/configs/A13-OLinuXino_defconfig
+++ b/configs/A13-OLinuXino_defconfig
@@ -4,6 +4,7 @@ CONFIG_FDTFILE="sun5i-a13-olinuxino.dtb"
CONFIG_USB1_VBUS_PIN="PG11"
CONFIG_VIDEO_HDMI=n
CONFIG_VIDEO_VGA_VIA_LCD=y
+CONFIG_VIDEO_VGA_VIA_LCD_FORCE_SYNC_ACTIVE_HIGH=y
# For use with the Olimex 7" LCD module, adjust timings for other displays
# Set video-mode=sunxi:800x600-24 at 60,monitor=lcd in the env. to enable
CONFIG_VIDEO_LCD_MODE="x:800,y:480,depth:18,pclk_khz:33000,le:16,ri:209,up:22,lo:22,hs:30,vs:1,sync:3,vmode:0"
diff --git a/drivers/video/sunxi_display.c b/drivers/video/sunxi_display.c
index af728b5..f5f24fc 100644
--- a/drivers/video/sunxi_display.c
+++ b/drivers/video/sunxi_display.c
@@ -645,7 +645,8 @@ static int sunxi_lcdc_get_clk_delay(const struct ctfb_res_modes *mode)
return (delay > 30) ? 30 : delay;
}

-static void sunxi_lcdc_tcon0_mode_set(const struct ctfb_res_modes *mode)
+static void sunxi_lcdc_tcon0_mode_set(const struct ctfb_res_modes *mode,
+ bool for_ext_vga_dac)
{
struct sunxi_lcdc_reg * const lcdc =
(struct sunxi_lcdc_reg *)SUNXI_LCD0_BASE;
@@ -719,6 +720,11 @@ static void sunxi_lcdc_tcon0_mode_set(const struct ctfb_res_modes *mode)
val |= SUNXI_LCDC_TCON_HSYNC_MASK;
if (!(mode->sync & FB_SYNC_VERT_HIGH_ACT))
val |= SUNXI_LCDC_TCON_VSYNC_MASK;
+
+#ifdef CONFIG_VIDEO_VGA_VIA_LCD_FORCE_SYNC_ACTIVE_HIGH
+ if (for_ext_vga_dac)
+ val = 0;
+#endif
writel(val, &lcdc->tcon0_io_polarity);

writel(0, &lcdc->tcon0_io_tristate);
@@ -1015,7 +1021,7 @@ static void sunxi_mode_set(const struct ctfb_res_modes *mode,
hitachi_tx18d42vm_init();
}
sunxi_composer_mode_set(mode, address);
- sunxi_lcdc_tcon0_mode_set(mode);
+ sunxi_lcdc_tcon0_mode_set(mode, false);
sunxi_composer_enable();
sunxi_lcdc_enable();
#ifdef CONFIG_VIDEO_LCD_SSD2828
@@ -1033,7 +1039,7 @@ static void sunxi_mode_set(const struct ctfb_res_modes *mode,
sunxi_vga_enable();
#elif defined CONFIG_VIDEO_VGA_VIA_LCD
sunxi_composer_mode_set(mode, address);
- sunxi_lcdc_tcon0_mode_set(mode);
+ sunxi_lcdc_tcon0_mode_set(mode, true);
sunxi_composer_enable();
sunxi_lcdc_enable();
sunxi_vga_external_dac_enable();
--
2.1.0