diff options
| author | Uwe Kleine-König <u.kleine-koenig@baylibre.com> | 2025-07-28 18:00:18 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-28 16:30:58 +0200 |
| commit | d10700cbd1f082398764df1829f3f65af51aef07 (patch) | |
| tree | 5cb60558e0e4a96c5820a6ad1a4dc3105b88ac4a /drivers/pwm/pwm-mediatek.c | |
| parent | 6dff1cf891f53d6ed654f56e0c05a1f8a8e13215 (diff) | |
pwm: mediatek: Fix duty and period setting
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/6d1fa87a76f8020bfe3171529b8e19baffceab10.1753717973.git.u.kleine-koenig@baylibre.com
Cc: stable@vger.kernel.org
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/pwm/pwm-mediatek.c')
| -rw-r--r-- | drivers/pwm/pwm-mediatek.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c index f0afbabb7dc1..bfbfe7f2917b 100644 --- a/drivers/pwm/pwm-mediatek.c +++ b/drivers/pwm/pwm-mediatek.c @@ -164,7 +164,10 @@ 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, @@ -187,9 +190,16 @@ 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); @@ -218,11 +228,8 @@ 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; } |