From: Jon Hunter jonathanh@nvidia.com
[ Upstream commit f271946117dde2ca8741b8138b347b2d68e6ad56 ]
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 Signed-off-by: Thierry Reding thierry.reding@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pwm/pwm-tegra.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c index 11a10b575ace..2735a97906fd 100644 --- a/drivers/pwm/pwm-tegra.c +++ b/drivers/pwm/pwm-tegra.c @@ -142,8 +142,8 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, * source clock rate as required_clk_rate, PWM controller will * be able to configure the requested period. */ - required_clk_rate = - (NSEC_PER_SEC / period_ns) << PWM_DUTY_WIDTH; + required_clk_rate = DIV_ROUND_UP_ULL(NSEC_PER_SEC << PWM_DUTY_WIDTH, + period_ns);
err = clk_set_rate(pc->clk, required_clk_rate); if (err < 0)