linux-kernel - Re: [PATCH v4 2/2] clk: bcm2835: Minimise clock jitter for PCM clock

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Message-ID: <20170602224526.GC20170@codeaurora.org>
Date:   Fri, 2 Jun 2017 15:45:26 -0700
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Phil Elwell <phil@...pberrypi.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Eric Anholt <eric@...olt.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        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 v4 2/2] clk: bcm2835: Minimise clock jitter for PCM clock

On 06/01, Phil Elwell wrote:
> Fractional clock dividers generate accurate average frequencies but
> with jitter, particularly when the integer divisor is small.
> 
> Introduce a new metric of clock accuracy to penalise clocks with a good
> average but worse jitter compared to clocks with an average which is no
> better but with lower jitter. The metric is the ideal rate minus the
> worse deviation from that ideal using the nearest integer divisors.
> 
> Use this metric for parent selection for clocks requiring low jitter
> (currently just PCM).
> 
> Signed-off-by: Phil Elwell <phil@...pberrypi.org>
> Reviewed-by: Eric Anholt <eric@...olt.net>
> Acked-by: Stefan Wahren <stefan.wahren@...e.com>
> ---

Applied to clk-next

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