Re: [PATCH V2 2/2] pwm: tegra: Ensure the clock rate is not less than needed

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

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On Fri, Oct 28, 2022 at 01:33:56PM +0100, Jon Hunter wrote:
> When dynamically scaling the PWM clock, the function
> dev_pm_opp_set_rate() may set the PWM clock to a rate that is lower than
> what is required. The clock rate requested when calling
> dev_pm_opp_set_rate() is the minimum clock rate that is needed to drive
> the PWM to achieve the required period. Hence, if the actual clock
> rate is less than the requested clock rate, then the required period
> cannot be achieved and configuring the PWM fails. Fix this by
> calling clk_round_rate() to check if the clock rate that will be provided
> is sufficient and if not, double the required clock rate to ensure the
> required period can be attained.
> 
> Fixes: 8c193f4714df ("pwm: tegra: Optimize period calculation")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> ---
> Changes since V1:
> - Multiplied the required_clk_rate by 2 instead of adding 1 to the
>   PWM_DUTY_WIDTH and recalculating the rate. Overall rate should be
>   similar.
> - Updated comment based upon Uwe's feedback.
> 
>  drivers/pwm/pwm-tegra.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)

Uwe, any objections to this? I'm assuming not, since you proposed this
variant yourself, but would be good to get your Acked-by nevertheless.

Thanks,
Thierry

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