Re: [PATCH V2 1/2] pwm: tegra: Improve required rate calculation

[Thierry Reding <thierry.reding@gmail.com>]

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On Fri, Oct 28, 2022 at 01:33:55PM +0100, Jon Hunter wrote:
> For the case where dev_pm_opp_set_rate() is called to set the PWM clock
> rate, the requested rate is calculated as ...
> 
>  required_clk_rate = (NSEC_PER_SEC / period_ns) << PWM_DUTY_WIDTH;
> 
> The above calculation may lead to rounding errors because the
> NSEC_PER_SEC is divided by 'period_ns' before applying the
> PWM_DUTY_WIDTH multiplication factor. For example, if the period is
> 45334ns, the above calculation yields a rate of 5646848Hz instead of
> 5646976Hz. Fix this by applying the multiplication factor before
> dividing and using the DIV_ROUND_UP macro which yields the expected
> result of 5646976Hz.
> 
> Fixes: 1d7796bdb63a ("pwm: tegra: Support dynamic clock frequency configuration")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
> Changes since V1:
> - Dropped extra parenthesis
> 
>  drivers/pwm/pwm-tegra.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Applied, thanks.

Thierry

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