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

Ian Campbell
2015-01-28T12:05:56Z

On Wed, 2015-01-28 at 11:47 +0100, Hans de Goede wrote:
> 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>

Acked-by: Ian Campbell <ijc@hellion.org.uk>

Although I might have been tempted to adjust mode->sync in the caller or
the place which populates it in the first place, just due to a general
dislike of boolean params to functions (which are opaque at the caller)
and to keep mode in sync with reality (if that matters).

Ian.

> ---
> 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();