I received a report that 4K resolution doesn't work if U-Boot video driver is disabled. It turns out that HDMI PHY clock driver was initialized prematurely, before reset line was deasserted and clocks enabled. U-Boot video driver masked the issue because it set pixel clock correctly.
In the process of researching the bug, I also found out that few bits in HDMI PHY registers were not set correctly. While there is no noticeable change (4K resolution works with both settings), I've added fix anyway, to be conformant with vendor documentation. Please check it out. Best regards, Jernej Jernej Skrabec (2): drm/sun4i: Fix sun8i HDMI PHY clock initialization drm/sun4i: Fix sun8i HDMI PHY configuration for > 148.5 MHz drivers/gpu/drm/sun4i/sun8i_hdmi_phy.c | 29 ++++++++++++++------------ 1 file changed, 16 insertions(+), 13 deletions(-) -- 2.21.0 -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/linux-sunxi/20190514204337.11068-1-jernej.skrabec%40siol.net. For more options, visit https://groups.google.com/d/optout.
