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sunxi: video: Force h/vsync active high when using ext. vga dac on some boards

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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>
This commit is contained in:
Hans de Goede
2015-01-25 15:33:07 +01:00
parent 8d0df9be92
commit fb75d972ea
4 changed files with 21 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/video/sunxi_display.c
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@@ -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();