Måns Rullgård mans@mansr.com writes:
Frank Oltmanns frank@oltmanns.dev writes:
Hi Måns,
21.05.2024 15:43:10 Måns Rullgård mans@mansr.com:
Frank Oltmanns frank@oltmanns.dev writes:
The Allwinner SoC's typically have an upper and lower limit for their clocks' rates. Up until now, support for that has been implemented separately for each clock type.
Implement that functionality in the sunxi-ng's common part making use of the CCF rate liming capabilities, so that it is available for all clock types.
Suggested-by: Maxime Ripard mripard@kernel.org Signed-off-by: Frank Oltmanns frank@oltmanns.dev Cc: stable@vger.kernel.org
drivers/clk/sunxi-ng/ccu_common.c | 19 +++++++++++++++++++ drivers/clk/sunxi-ng/ccu_common.h | 3 +++ 2 files changed, 22 insertions(+)
This just landed in 6.6 stable, and it broke HDMI output on an A20 based device, the clocks ending up all wrong as seen in this diff of /sys/kernel/debug/clk/clk_summary:
[...]
Reverting this commit makes it work again.
Thank you for your detailed report!
I've had a first look at hdmi-tmds and hdmi-ddc, and neither seems to be calling ccu_is_better_rate() in their determine_rate() functions. Their parents have the exact same rates in your diff, so, my current working assumption is that they can't be the cause either.
I'll have a more detailed look over the weekend. Until then, if anyone has some ideas where I should have a look next, please share your thoughts.
In case it's relevant, this system doesn't use the HDMI DDC, the physical DDC pins being connected to a different I2C adapter for various reasons.
From the clk_summary diff, I see a few things:
- hdmi-tmds has changed parent from pll-video1-2x to pll-video0-2x.
- The ratio of hdmi-tmds to its parent has changed from 1/8 to 1.
- The resulting rate bears no relation to the pixel clock from EDID.
I tried kernel 6.9.1 as well, and that doesn't work either. I'll keep digging and try to narrow it down.
It turns out HDMI output is broken in v6.9 for a different reason. However, this commit (b914ec33b391 clk: sunxi-ng: common: Support minimum and maximum rate) requires two others as well in order not to break things on the A20:
cedb7dd193f6 drm/sun4i: hdmi: Convert encoder to atomic 9ca6bc246035 drm/sun4i: hdmi: Move mode_set into enable
With those two (the second depends on the first) cherry-picked on top of v6.6.31, the HDMI output is working again. Likewise on v6.8.10.