[0/2] dts: Add CEC clock to DW HDMI

Message

Jernej Škrabec Nov. 20, 2021, 7:34 a.m. UTC

Experimentation proved that CEC controller in H3-like DW-HDMI core
depends on 32 kHz clock output from RTC. If board has external 32768 Hz
crystal, HDMI CEC always work. However, if external crystal is missing
and 32 kHz clock is generated by internal oscillator, CEC communication
may or may not work, depending on accuracy. Changing internal oscillator
prescaler can make CEC work.

This was totally missed when implementing HDMI support, because user
manual has no CEC information besides the fact that it exists.

Please take a look.

Best regards,
Jernej

Jernej Skrabec (2):
  arm64: dts: allwinner: a64: Add CEC clock to HDMI
  ARM: dts: sunxi: Add CEC clock to DW-HDMI

 arch/arm/boot/dts/sun8i-r40.dtsi              | 4 ++--
 arch/arm/boot/dts/sunxi-h3-h5.dtsi            | 4 ++--
 arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

Comments

Maxime Ripard Nov. 22, 2021, 9:07 a.m. UTC | #1

On Sat, 20 Nov 2021 08:34:46 +0100, Jernej Skrabec wrote:
> Experimentation proved that CEC controller in H3-like DW-HDMI core
> depends on 32 kHz clock output from RTC. If board has external 32768 Hz
> crystal, HDMI CEC always work. However, if external crystal is missing
> and 32 kHz clock is generated by internal oscillator, CEC communication
> may or may not work, depending on accuracy. Changing internal oscillator
> prescaler can make CEC work.
> 
> [...]

Applied to sunxi/linux.git (sunxi/dt-for-5.17).

Thanks!
Maxime