The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x f21d136caf8171f94159d975ea4620c164431bd9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025082142-splotchy-hypocrite-964a@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f21d136caf8171f94159d975ea4620c164431bd9 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= u.kleine-koenig@baylibre.com Date: Mon, 28 Jul 2025 18:00:18 +0200 Subject: [PATCH] pwm: mediatek: Fix duty and period setting MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
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
diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c index b6560e52c803..e4b595fc5a5e 100644 --- a/drivers/pwm/pwm-mediatek.c +++ b/drivers/pwm/pwm-mediatek.c @@ -170,7 +170,10 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm, 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, @@ -193,9 +196,16 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm, }
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); @@ -224,11 +234,8 @@ static int pwm_mediatek_apply(struct pwm_chip *chip, struct pwm_device *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; }