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

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Date:   Sat, 15 Jun 2019 11:17:10 +0200
From:   Jernej Škrabec <jernej.skrabec@...l.net>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     a.hajda@...sung.com, Laurent.pinchart@...asonboard.com,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Jonas Karlman <jonas@...boo.se>,
        Heiko Stuebner <heiko@...ech.de>,
        Jerome Brunet <jbrunet@...libre.com>
Subject: Re: [PATCH] drm/bridge: dw-hdmi: Use automatic CTS generation mode when using non-AHB audio

Dne sreda, 12. junij 2019 ob 10:51:47 CEST je Neil Armstrong napisal(a):
> 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@...l.net>
> Cc: Maxime Ripard <maxime.ripard@...tlin.com>
> Cc: Jonas Karlman <jonas@...boo.se>
> Cc: Heiko Stuebner <heiko@...ech.de>
> Cc: Jerome Brunet <jbrunet@...libre.com>
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>

Tested-by: Jernej Skrabec <jernej.skrabec@...l.net>
Reviewed-by: Jernej Skrabec <jernej.skrabec@...l.net>

Best regards,
Jernej