linux-kernel - Re: [PATCH v2 0/2] clk: bcm2835: PCM clock improvements

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Message-ID: <d9c1303d-a170-bb83-f9a9-94f201e4ac2c@i2se.com>
Date:   Wed, 31 May 2017 16:58:01 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Phil Elwell <phil@...pberrypi.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Eric Anholt <eric@...olt.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        linux-clk@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] clk: bcm2835: PCM clock improvements

Am 31.05.2017 um 11:18 schrieb Phil Elwell:
> The switch to using the upstream bcm2835_cprman clock driver caused a
> few problems for users of PCM (I2S) peripherals. Audio applications
> require accurate, stable clocks, and the cprman driver wasn't
> conservative enough in its choice of clock sources.
>
> These patches restrict the clock sources for the PCM peripheral in two
> ways: the first causes all possible sources except OSC and PLLD_PER
> to be ignored, while the second allows clocks to be specified as
> "low_jitter", causing the effects of fractional divisors to be taken
> into account when comparing potential clocks for accuracy. In practice,
> the combined effect of the two patches is to choose OSC as a source if
> an integer divisor can be used, otherwise PLLD_PER is chosen.
>
> Changes in v2:
> * Extended bcm2835_pcm_per_parents to cover the pllh_aux slot, and gave
>   it a comment in patch 1.
> * Added a REGISTER_PCM_CLK analagous to REGISTER_PER_CLK in patch 1.
> * Renamed temporary variable idiv to int_div in patch 2.
>
> Phil Elwell (2):
>   clk: bcm2835: Limit PCM clock to OSC and PLLD_PER
>   clk: bcm2835: Minimise clock jitter for PCM clock
>
>  drivers/clk/bcm/clk-bcm2835.c | 50 ++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 45 insertions(+), 5 deletions(-)
>
For the whole series:

Acked-by: Stefan Wahren <stefan.wahren@...e.com>

I hope Eric as the author of the driver has a chance to look over the
patches.

Stefan