The PWM allow configuring the PWM resolution from 8 bits PWM values up to 15 bits values, for the Hi-Res PWMs, and then either 6-bit or 9-bit for the normal PWMs. The current implementation loops through all possible resolutions (PWM sizes), for the PWM subtype, on top of the already existing process of determining the prediv, exponent and refclk.
The first and second issues are related to capping the computed PWM value.
The third issue is that it uses the wrong maximum possible PWM value for determining the best matched period.
Fix all of them.
Signed-off-by: Abel Vesa abel.vesa@linaro.org --- Changes in v3: - Added a new patch that fixes the normal PWMs, since they now support 6-bit resolution as well. Added it as first patch. - Re-worded the second patch. Included Bjorn's suggestion and R-b tag. - Link to v2: https://lore.kernel.org/r/20250226-leds-qcom-lpg-fix-max-pwm-on-hi-res-v2-0-...
Changes in v2: - Re-worded the commit to drop the details that are not important w.r.t. what the patch is fixing. - Added another patch which fixes the resolution used for determining best matched period and PWM config. - Link to v1: https://lore.kernel.org/r/20250220-leds-qcom-lpg-fix-max-pwm-on-hi-res-v1-1-...
--- Abel Vesa (3): leds: rgb: leds-qcom-lpg: Fix pwm resolution max for normal PWMs leds: rgb: leds-qcom-lpg: Fix pwm resolution max for Hi-Res PWMs leds: rgb: leds-qcom-lpg: Fix calculation of best period Hi-Res PWMs
drivers/leds/rgb/leds-qcom-lpg.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) --- base-commit: cd3215bbcb9d4321def93fea6cfad4d5b42b9d1d change-id: 20250220-leds-qcom-lpg-fix-max-pwm-on-hi-res-067e8782a79b
Best regards,
Ideally, the requested duty cycle should never translate to a PWM value higher than the selected resolution (PWM size), but currently the best matched period is never reported back to the PWM consumer, so the consumer will still be using the requested period which is higher than the best matched one. This will result in PWM consumer requesting duty cycle values higher than the allowed PWM value.
In case of Hi-Res PWMs, the current implementation is capping the PWM value at a 15-bit resolution, even when the lower resolutions are selected.
Fix the issue by capping the PWM value to the maximum value allowed by the selected resolution.
Cc: stable@vger.kernel.org # 6.4 Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM") Reviewed-by: Bjorn Andersson andersson@kernel.org Signed-off-by: Abel Vesa abel.vesa@linaro.org --- drivers/leds/rgb/leds-qcom-lpg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c index 4454fc6a38480b61916318dd170f3eddc32976d6..0b6310184988c299d82ee7181982c03d306407a4 100644 --- a/drivers/leds/rgb/leds-qcom-lpg.c +++ b/drivers/leds/rgb/leds-qcom-lpg.c @@ -530,7 +530,7 @@ static void lpg_calc_duty(struct lpg_channel *chan, uint64_t duty) unsigned int clk_rate;
if (chan->subtype == LPG_SUBTYPE_HI_RES_PWM) { - max = LPG_RESOLUTION_15BIT - 1; + max = BIT(lpg_pwm_resolution_hi_res[chan->pwm_resolution_sel]) - 1; clk_rate = lpg_clk_rates_hi_res[chan->clk_sel]; } else { max = BIT(lpg_pwm_resolution[chan->pwm_resolution_sel]) - 1;
Hi,
On Mon, Mar 03, 2025 at 01:52:51PM +0200, Abel Vesa wrote:
Ideally, the requested duty cycle should never translate to a PWM value higher than the selected resolution (PWM size), but currently the best matched period is never reported back to the PWM consumer, so the consumer will still be using the requested period which is higher than the best matched one. This will result in PWM consumer requesting duty cycle values higher than the allowed PWM value.
In case of Hi-Res PWMs, the current implementation is capping the PWM value at a 15-bit resolution, even when the lower resolutions are selected.
Fix the issue by capping the PWM value to the maximum value allowed by the selected resolution.
Cc: stable@vger.kernel.org # 6.4 Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM") Reviewed-by: Bjorn Andersson andersson@kernel.org Signed-off-by: Abel Vesa abel.vesa@linaro.org
Reviewed-by: Sebastian Reichel sre@kernel.org
Greetings,
-- Sebastian
drivers/leds/rgb/leds-qcom-lpg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c index 4454fc6a38480b61916318dd170f3eddc32976d6..0b6310184988c299d82ee7181982c03d306407a4 100644 --- a/drivers/leds/rgb/leds-qcom-lpg.c +++ b/drivers/leds/rgb/leds-qcom-lpg.c @@ -530,7 +530,7 @@ static void lpg_calc_duty(struct lpg_channel *chan, uint64_t duty) unsigned int clk_rate; if (chan->subtype == LPG_SUBTYPE_HI_RES_PWM) {
max = LPG_RESOLUTION_15BIT - 1;
max = BIT(lpg_pwm_resolution_hi_res[chan->pwm_resolution_sel]) - 1;-- 2.34.1
When determining the actual best period by looping through all possible PWM configs, the resolution currently used is based on bit shift value which is off-by-one above the possible maximum PWM value allowed.
So subtract one from the resolution before determining the best period so that the maximum duty cycle requested by the PWM user won't result in a value above the maximum allowed.
Cc: stable@vger.kernel.org # 6.4 Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM") Signed-off-by: Abel Vesa abel.vesa@linaro.org --- drivers/leds/rgb/leds-qcom-lpg.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c index 0b6310184988c299d82ee7181982c03d306407a4..4f2a178e3d265a2cc88e651d3e2ca6ae3dfac2e2 100644 --- a/drivers/leds/rgb/leds-qcom-lpg.c +++ b/drivers/leds/rgb/leds-qcom-lpg.c @@ -462,7 +462,7 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period) max_res = LPG_RESOLUTION_9BIT; }
- min_period = div64_u64((u64)NSEC_PER_SEC * (1 << pwm_resolution_arr[0]), + min_period = div64_u64((u64)NSEC_PER_SEC * ((1 << pwm_resolution_arr[0]) - 1), clk_rate_arr[clk_len - 1]); if (period <= min_period) return -EINVAL; @@ -483,7 +483,7 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period) */
for (i = 0; i < pwm_resolution_count; i++) { - resolution = 1 << pwm_resolution_arr[i]; + resolution = (1 << pwm_resolution_arr[i]) - 1; for (clk_sel = 1; clk_sel < clk_len; clk_sel++) { u64 numerator = period * clk_rate_arr[clk_sel];
@@ -1292,7 +1292,7 @@ static int lpg_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, if (ret) return ret;
- state->period = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC * (1 << resolution) * + state->period = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC * ((1 << resolution) - 1) * pre_div * (1 << m), refclk); state->duty_cycle = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC * pwm_value * pre_div * (1 << m), refclk); } else {
Hi,
On Mon, Mar 03, 2025 at 01:52:52PM +0200, Abel Vesa wrote:
When determining the actual best period by looping through all possible PWM configs, the resolution currently used is based on bit shift value which is off-by-one above the possible maximum PWM value allowed.
So subtract one from the resolution before determining the best period so that the maximum duty cycle requested by the PWM user won't result in a value above the maximum allowed.
Cc: stable@vger.kernel.org # 6.4 Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM") Signed-off-by: Abel Vesa abel.vesa@linaro.org
Reviewed-by: Sebastian Reichel sre@kernel.org
Greetings,
-- Sebastian
drivers/leds/rgb/leds-qcom-lpg.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c index 0b6310184988c299d82ee7181982c03d306407a4..4f2a178e3d265a2cc88e651d3e2ca6ae3dfac2e2 100644 --- a/drivers/leds/rgb/leds-qcom-lpg.c +++ b/drivers/leds/rgb/leds-qcom-lpg.c @@ -462,7 +462,7 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period) max_res = LPG_RESOLUTION_9BIT; }
- min_period = div64_u64((u64)NSEC_PER_SEC * (1 << pwm_resolution_arr[0]),
- min_period = div64_u64((u64)NSEC_PER_SEC * ((1 << pwm_resolution_arr[0]) - 1), clk_rate_arr[clk_len - 1]); if (period <= min_period) return -EINVAL;
@@ -483,7 +483,7 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period) */ for (i = 0; i < pwm_resolution_count; i++) {
resolution = 1 << pwm_resolution_arr[i];
resolution = (1 << pwm_resolution_arr[i]) - 1;@@ -1292,7 +1292,7 @@ static int lpg_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, if (ret) return ret;
state->period = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC * (1 << resolution) *
state->period = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC * ((1 << resolution) - 1) * pre_div * (1 << m), refclk);-- 2.34.1
Hello,
On Mon, Mar 03, 2025 at 01:52:49PM +0200, Abel Vesa wrote:
The PWM allow configuring the PWM resolution from 8 bits PWM values up to 15 bits values, for the Hi-Res PWMs, and then either 6-bit or 9-bit for the normal PWMs. The current implementation loops through all possible resolutions (PWM sizes), for the PWM subtype, on top of the already existing process of determining the prediv, exponent and refclk.
The first and second issues are related to capping the computed PWM value.
I just took a very quick look. I'd say squash the first and second patch into a single one. Splitting a change that fixes the same issue in the two branches of an if condition has no benefit.
Other than that this patch set would also benefit from what I wrote in the review of the other patch you send: Please mention a request where the result becomes wrong. This considerably simplifies understanding your changes.
Thanks Uwe
linux-stable-mirror@lists.linaro.org
-
Abel Vesa -
Sebastian Reichel -
Uwe Kleine-König