linux-kernel - Re: [PATCH 0/3] ARM: sun8i: a33: Audio codec improvements

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Date:   Wed, 5 Dec 2018 12:09:39 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH 0/3] ARM: sun8i: a33: Audio codec improvements

On Wed, Dec 05, 2018 at 06:11:49PM +0800, Chen-Yu Tsai wrote:
> Hi everyone,
> 
> This series improves audio support on the A33. Like other Allwinner
> SoCs, the A33 requires the use of a sigma-delta modulation fractional-N
> PLL to generate the correct clock used for audio playback. Otherwise the
> pitch would be slightly off.
> 
> Patch 1 enables sigma-delta modulation for the audio PLL on the A33.
> 
> Patch 2 is only slightly related. It sets the CLK_SET_RATE_PARENT flag
> for all audio-related module clocks
> 
> Patch 3 lowers the audio codec's oversampling rate, so that it can
> play back audio sampled at beyond 48 KHz.
> 
> This is the same as what has recently been done for the A64, which
> shares the same audio codec hardware design.
> 
> However, on the A33 it seems the PLL doesn't always immediately lock on
> to the new clock frequency when there is a rate change. Also since the
> codec is only put in standby instead of turned off, runtime PM never
> kicks in, and the audio related clocks never get turned off. I'm still
> looking into this.
> 
> On an unrelated note, if you get pops when playing back audio on sunxi,
> it might be related to cpufreq. Try setting the governor to performance
> and see if that removes the pops.

Applied all 3 patches, thanks!
Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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