HDMI/DVI spurious failure

[Maxime Ripard]

Hi,

(Sending those kind of bug reports to linux-sunxi doesn't really work,
you should Cc at least the ML involved in the development of the
driver at fault).

On Mon, Jan 14, 2019 at 01:29:34PM +0000, Priit Laes wrote:
> I have a somewhat curious case with one HDMI/DVI screen that fails
> to initialize properly every 6-7 boots. The display itself is also
> somewhat flawed (missing HPD pin and the VSYNC/HSYNC pulse width
> is set to 0 in EDID), but I suspect there could be some issues
> regarding timing in A20 HDMI driver in Linux.
> 
> HW: Olinuxino Lime2 eMMC
> 
> The same display works out of the box on Raspberry Pi. And I
> haven't seen it failing in u-boot on A20 Lime2 hw.
> 
> I have disabled HDMI support in U-boot (there's another issue
> with simplefb handover to modesetting, but I currently try to
> leave u-boot out of the equation), so kernel itselfs sets up
> the display.
> Basically the only differences I have found are some timing
> differences in DRM logs and following discrepancey in clock
> tree when comparing failing and working boots:
> 
> --- clks-failing.dump	2019-01-14 14:45:24.026279493 +0200
> +++ clks-ok.dump	2019-01-14 14:29:59.799715126 +0200
> @@ -6,7 +6,7 @@
>   mii_phy_tx               0        0        0    25000000          0     0  50000
>   osc32k                   0        0        0       32768          0     0  50000
>   osc24M                   2        2        1    24000000          0     0  50000
> -    hosc                  5        5        1    24000000          0     0  50000
> +    hosc                  6        6        1    24000000          0     0  50000
>         out-b              0        0        0       32000          0     0  50000
>         out-a              0        0        0       32000          0     0  50000
>         hdmi1-slow         0        0        0    24000000          0     0  50000
> @@ -52,10 +52,10 @@
>            apb1-i2c1       1        1        0    24000000          0     0  50000
>            apb1-i2c0       1        1        0    24000000          0     0  50000
>         pll-gpu            0        0        0  1200000000          0     0  50000
> -       pll-video1         0        0        0   327000000          0     0  50000
> -          pll-video1-2x   0        0        0   654000000          0     0  50000
> -             hdmi-tmds    0        0        0    25153846          0     0  50000
> -                hdmi-ddc  0        0        0       89835          0     0  50000
> +       pll-video1         1        1        0   327000000          0     0  50000
> +          pll-video1-2x   1        1        0   654000000          0     0  50000
> +             hdmi-tmds    1        1        0    25153846          0     0  50000
> +                hdmi-ddc  1        1        0       89835          0     0  50000
>         pll-periph-base    3        3        0  1200000000          0     0  50000
>            mbus            1        1        0   300000000          0     0  50000
>            pll-periph-sata 1        1        0   100000000          0     0  50000
> 
> 
> Any hints what else to debug?

It doesn't look related to the clock rate itself, since it doesn't
change between the two cases. However, in one case the DDC clock is
enabled and in the other it's disabled.

Was it taken at the same time? Maybe you can try with that patch?
http://code.bulix.org/z7jmkm-555344?raw

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com