6.6-stable review patch. If anyone has any objections, please let me know.
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From: Uwe Kleine-König u.kleine-koenig@baylibre.com
commit f21d136caf8171f94159d975ea4620c164431bd9 upstream.
The period generated by the hardware is
(PWMDWIDTH + 1) << CLKDIV) / freq
according to my tests with a signal analyser and also the documentation.
The current algorithm doesn't consider the `+ 1` part and so configures slightly too high periods. The same issue exists for the duty cycle setting. So subtract 1 from both the register values for period and duty cycle. If period is 0, bail out, if duty_cycle is 0, just disable the PWM which results in a constant low output.
Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support") Signed-off-by: Uwe Kleine-König u.kleine-koenig@baylibre.com Reviewed-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Link: https://lore.kernel.org/r/6d1fa87a76f8020bfe3171529b8e19baffceab10.175371797... Cc: stable@vger.kernel.org Signed-off-by: Uwe Kleine-König ukleinek@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pwm/pwm-mediatek.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
--- a/drivers/pwm/pwm-mediatek.c +++ b/drivers/pwm/pwm-mediatek.c @@ -167,7 +167,10 @@ static int pwm_mediatek_config(struct pw do_div(resolution, clk_rate);
cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000, resolution); - while (cnt_period > 8191) { + if (!cnt_period) + return -EINVAL; + + while (cnt_period > 8192) { resolution *= 2; clkdiv++; cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000, @@ -190,9 +193,16 @@ static int pwm_mediatek_config(struct pw }
cnt_duty = DIV_ROUND_CLOSEST_ULL((u64)duty_ns * 1000, resolution); + pwm_mediatek_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv); - pwm_mediatek_writel(pc, pwm->hwpwm, reg_width, cnt_period); - pwm_mediatek_writel(pc, pwm->hwpwm, reg_thres, cnt_duty); + pwm_mediatek_writel(pc, pwm->hwpwm, reg_width, cnt_period - 1); + + if (cnt_duty) { + pwm_mediatek_writel(pc, pwm->hwpwm, reg_thres, cnt_duty - 1); + pwm_mediatek_enable(chip, pwm); + } else { + pwm_mediatek_disable(chip, pwm); + }
out: pwm_mediatek_clk_disable(chip, pwm); @@ -221,11 +231,8 @@ static int pwm_mediatek_apply(struct pwm if (err) return err;
- if (!pwm->state.enabled) { + if (!pwm->state.enabled) err = pwm_mediatek_clk_enable(chip, pwm); - if (!err) - pwm_mediatek_enable(chip, pwm); - }
return err; }