[PATCH v2] arm64: dts: rockchip: Adjust the HDMI DDC IO driver strength for rk3588

[Nicolas Frattaroli]

On Thursday, 22 May 2025 04:05:24 Central European Summer Time Andy Yan wrote:
> From: Andy Yan <andy.yan at rock-chips.com>
> 
> For the RK3588 HDMI controller, the falling edge of DDC SDA and SCL
> almost coincide and cannot be adjusted by HDMI registrer, resulting
> in poor compatibility of DDC communication.
> 
> An improvement of the compatibility of DDC can be done by increasing
> the driver strength of SCL and decreasing the driver strength of SDA
> to increase the slope of the falling edge.
> 
> It should be noted that the maximum driving strength of hdmim0_tx1_scl
> is only 3, which is different from that of the other IOs.
> 
> Signed-off-by: Andy Yan <andy.yan at rock-chips.com>
> 
> ---
> 
> Changes in v2:
> - Correct the max drive level of hdmim0_tx1_scl.
> 
>  .../dts/rockchip/rk3588-base-pinctrl.dtsi     | 20 +++++------
>  .../dts/rockchip/rk3588-extra-pinctrl.dtsi    |  5 +--
>  .../boot/dts/rockchip/rockchip-pinconf.dtsi   | 35 +++++++++++++++++++
>  3 files changed, 48 insertions(+), 12 deletions(-)
> 

Tested-by: Nicolas Frattaroli <nicolas.frattaroli at collabora.com>

Quickly tested this on both HDMI ports of a ROCK 5T with an HDMI capture
card on the other end. While I didn't originally have any issues to begin
with, this patch does not introduce any new ones, so seems good to me.