Re: [PATCH] drm/bridge: dw-hdmi: Use automatic CTS generation mode when using non-AHB audio

From: Doug Anderson
Date: Wed Jun 19 2019 - 17:28:18 EST


On Wed, Jun 12, 2019 at 1:51 AM Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote:
> When using an I2S source using a different clock source (usually the I2S
> audio HW uses dedicated PLLs, different from the HDMI PHY PLL), fixed
> CTS values will cause some frequent audio drop-out and glitches as
> reported on Amlogic, Allwinner and Rockchip SoCs setups.
> Setting the CTS in automatic mode will let the HDMI controller generate
> automatically the CTS value to match the input audio clock.
> The DesignWare DW-HDMI User Guide explains:
> For Automatic CTS generation
> Write "0" on the bit field "CTS_manual", Register 0x3205: AUD_CTS3
> The DesignWare DW-HDMI Databook explains :
> If "CTS_manual" bit equals 0b this registers contains "audCTS[19:0]"
> generated by the Cycle time counter according to specified timing.
> Cc: Jernej Skrabec <jernej.skrabec@xxxxxxxx>
> Cc: Maxime Ripard <maxime.ripard@xxxxxxxxxxx>
> Cc: Jonas Karlman <jonas@xxxxxxxxx>
> Cc: Heiko Stuebner <heiko@xxxxxxxxx>
> Cc: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 44 +++++++++++++++--------
> 1 file changed, 29 insertions(+), 15 deletions(-)

Tested-by: Douglas Anderson <dianders@xxxxxxxxxxxx>