On Fri, Jan 18, 2019 at 02:51:26PM +0000, Priit Laes wrote: > On Fri, Jan 18, 2019 at 03:04:18PM +0100, Maxime Ripard wrote: > > On Fri, Jan 18, 2019 at 10:10:53AM +0000, Priit Laes wrote: > > > > > > > > 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 > > > > > > > > > > > > > > Thanks, after doing ~50+ boots I haven't seen a single failure. > > > > > > > > > > > > > > Previously I had following failure cases which are now both fixed: > > > > > > > > > > > > > > a) Linux without u-boot HDMI, where one in every 6-7 boots failed. > > > > > > > b) u--boot with hdmi enabled switching to simplefb and then switching > > > > > > > to kms, where previously all boots ended up with garbled screen. > > > > > > > > > > > > So it's not really a fix, but it really looks like the clock is not > > > > > > enabled when it should. > > > > > > > > > > > > Can you describe your test scenario a bit more? What are you doing > > > > > > exactly, just booting? When do you start using the display? When did > > > > > > you capture the debugfs output that you pasted? > > > > > > > > > > Display is already connected via HDMI to the board. I don't really > > > > > remove it, I just boot the device and let it start Xorg. > > > > > Meanwhile I just ssh into the device and capture debugfs output. > > > > > See my 3 testing scenarios below. > > > > > > > > > > Kernel also includes one extra patch to fall back to DDC, in case HPD > > > > > fails. Mostly the same I already submitted last November [1]. > > > > > > > > Do you have the same issue without that patch? > > > > > > Can't really test this display without this patch and I do not have other > > > HDMI/DVI screens. And this issue does not happen with other HDMI displays > > > that I have here. > > > > Can't you just force the monitor to be reported as present? It's not > > great and we don't want to merge it, but that would allow you to test > > that setup without too many interferences. > > Baseline is clean u-boot / linux. U-boot does not detect/enable display. > > 1) Booting Linux with drm.debug=0xe > > * Linux does not detect/enable display > > 2) Booting with drm.debug=0xe video=HDMI-A-1:640x480@60e > > * Linux detects display, but display is garbled, and proper edid data is detected: > > [snip] > 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 > [/snip] > > 3) Booting with drm.debug=0xe video=HDMI-A-1:640x480@60e > And also one extra patch for Linux where HDMI DDC clock marked as critical > > Linux detects and initializes display properly: > [snip] > 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 > [/snip] I guess you'll need to track down when the hdmi-tmds and hdmi-ddc are enabled and disabled, and if it makes sense :/ Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
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