The introduction of high resolution PWM support changed the order of the
operations in the calculation of min and max period. The result in both
divisions is in most cases a truncation to 0, which limits the period to
the range of [0, 0].
Both numerators (and denominators) are within 64 bits, so the whole
expression can be put directly into the div64_u64, instead of doing it
partially.
Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM")
Reviewed-by: Caleb Connolly <[email protected]>
Tested-by: Steev Klimaszewski <[email protected]>
Signed-off-by: Bjorn Andersson <[email protected]>
---
Changes since v1:
- Reworded first sentence to express that it's the order and not the
previously non-existent parenthesis that changed...
- Picked up review tags.
drivers/leds/rgb/leds-qcom-lpg.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c
index c9cea797a697..7287fadc00df 100644
--- a/drivers/leds/rgb/leds-qcom-lpg.c
+++ b/drivers/leds/rgb/leds-qcom-lpg.c
@@ -312,14 +312,14 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period)
max_res = LPG_RESOLUTION_9BIT;
}
- min_period = (u64)NSEC_PER_SEC *
- div64_u64((1 << pwm_resolution_arr[0]), clk_rate_arr[clk_len - 1]);
+ min_period = div64_u64((u64)NSEC_PER_SEC * (1 << pwm_resolution_arr[0]),
+ clk_rate_arr[clk_len - 1]);
if (period <= min_period)
return -EINVAL;
/* Limit period to largest possible value, to avoid overflows */
- max_period = (u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV *
- div64_u64((1 << LPG_MAX_M), 1024);
+ max_period = div64_u64((u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV * (1 << LPG_MAX_M),
+ 1024);
if (period > max_period)
period = max_period;
--
2.25.1
On Mon, May 15, 2023 at 09:26:04AM -0700, Bjorn Andersson wrote:
> The introduction of high resolution PWM support changed the order of the
> operations in the calculation of min and max period. The result in both
> divisions is in most cases a truncation to 0, which limits the period to
> the range of [0, 0].
>
> Both numerators (and denominators) are within 64 bits, so the whole
> expression can be put directly into the div64_u64, instead of doing it
> partially.
>
> Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM")
> Reviewed-by: Caleb Connolly <[email protected]>
> Tested-by: Steev Klimaszewski <[email protected]>
> Signed-off-by: Bjorn Andersson <[email protected]>
Tested-by: Johan Hovold <[email protected]>
Pavel or Lee, could you pick this one up for 6.4 as it fixes a
regression (e.g. broken backlight on a number of laptops like the X13s)?
> ---
>
> Changes since v1:
> - Reworded first sentence to express that it's the order and not the
> previously non-existent parenthesis that changed...
> - Picked up review tags.
>
> drivers/leds/rgb/leds-qcom-lpg.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c
> index c9cea797a697..7287fadc00df 100644
> --- a/drivers/leds/rgb/leds-qcom-lpg.c
> +++ b/drivers/leds/rgb/leds-qcom-lpg.c
> @@ -312,14 +312,14 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period)
> max_res = LPG_RESOLUTION_9BIT;
> }
>
> - min_period = (u64)NSEC_PER_SEC *
> - div64_u64((1 << pwm_resolution_arr[0]), clk_rate_arr[clk_len - 1]);
> + min_period = div64_u64((u64)NSEC_PER_SEC * (1 << pwm_resolution_arr[0]),
> + clk_rate_arr[clk_len - 1]);
> if (period <= min_period)
> return -EINVAL;
>
> /* Limit period to largest possible value, to avoid overflows */
> - max_period = (u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV *
> - div64_u64((1 << LPG_MAX_M), 1024);
> + max_period = div64_u64((u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV * (1 << LPG_MAX_M),
> + 1024);
> if (period > max_period)
> period = max_period;
Johan
On 15/05/2023 18:26, Bjorn Andersson wrote:
> The introduction of high resolution PWM support changed the order of the
> operations in the calculation of min and max period. The result in both
> divisions is in most cases a truncation to 0, which limits the period to
> the range of [0, 0].
>
> Both numerators (and denominators) are within 64 bits, so the whole
> expression can be put directly into the div64_u64, instead of doing it
> partially.
>
> Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM")
> Reviewed-by: Caleb Connolly <[email protected]>
> Tested-by: Steev Klimaszewski <[email protected]>
> Signed-off-by: Bjorn Andersson <[email protected]>
> ---
>
> Changes since v1:
> - Reworded first sentence to express that it's the order and not the
> previously non-existent parenthesis that changed...
> - Picked up review tags.
>
> drivers/leds/rgb/leds-qcom-lpg.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c
> index c9cea797a697..7287fadc00df 100644
> --- a/drivers/leds/rgb/leds-qcom-lpg.c
> +++ b/drivers/leds/rgb/leds-qcom-lpg.c
> @@ -312,14 +312,14 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period)
> max_res = LPG_RESOLUTION_9BIT;
> }
>
> - min_period = (u64)NSEC_PER_SEC *
> - div64_u64((1 << pwm_resolution_arr[0]), clk_rate_arr[clk_len - 1]);
> + min_period = div64_u64((u64)NSEC_PER_SEC * (1 << pwm_resolution_arr[0]),
> + clk_rate_arr[clk_len - 1]);
> if (period <= min_period)
> return -EINVAL;
>
> /* Limit period to largest possible value, to avoid overflows */
> - max_period = (u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV *
> - div64_u64((1 << LPG_MAX_M), 1024);
> + max_period = div64_u64((u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV * (1 << LPG_MAX_M),
> + 1024);
> if (period > max_period)
> period = max_period;
>
Tested-by: Neil Armstrong <[email protected]> # on SM8550-QRD
On Wed, 24 May 2023, Johan Hovold wrote:
> On Mon, May 15, 2023 at 09:26:04AM -0700, Bjorn Andersson wrote:
> > The introduction of high resolution PWM support changed the order of the
> > operations in the calculation of min and max period. The result in both
> > divisions is in most cases a truncation to 0, which limits the period to
> > the range of [0, 0].
> >
> > Both numerators (and denominators) are within 64 bits, so the whole
> > expression can be put directly into the div64_u64, instead of doing it
> > partially.
> >
> > Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM")
> > Reviewed-by: Caleb Connolly <[email protected]>
> > Tested-by: Steev Klimaszewski <[email protected]>
> > Signed-off-by: Bjorn Andersson <[email protected]>
>
> Tested-by: Johan Hovold <[email protected]>
>
> Pavel or Lee, could you pick this one up for 6.4 as it fixes a
> regression (e.g. broken backlight on a number of laptops like the X13s)?
I don't presently have any plans for a -fixes submission.
If anyone else would like to submit it, please be my guest:
Acked-by: Lee Jones <[email protected]>
--
Lee Jones [李琼斯]
On Fri, Jun 02, 2023 at 10:19:28AM +0100, Lee Jones wrote:
> On Wed, 24 May 2023, Johan Hovold wrote:
> > Pavel or Lee, could you pick this one up for 6.4 as it fixes a
> > regression (e.g. broken backlight on a number of laptops like the X13s)?
>
> I don't presently have any plans for a -fixes submission.
>
> If anyone else would like to submit it, please be my guest:
>
> Acked-by: Lee Jones <[email protected]>
That was not the answer I expected, but sure, I've sent it on to Linus:
https://lore.kernel.org/lkml/[email protected]/
Johan
On Sat, 03 Jun 2023, Johan Hovold wrote:
> On Fri, Jun 02, 2023 at 10:19:28AM +0100, Lee Jones wrote:
> > On Wed, 24 May 2023, Johan Hovold wrote:
>
> > > Pavel or Lee, could you pick this one up for 6.4 as it fixes a
> > > regression (e.g. broken backlight on a number of laptops like the X13s)?
> >
> > I don't presently have any plans for a -fixes submission.
> >
> > If anyone else would like to submit it, please be my guest:
> >
> > Acked-by: Lee Jones <[email protected]>
>
> That was not the answer I expected, but sure, I've sent it on to Linus:
Sorry, soooo busy right now. Trying not to drop too many plates.
> https://lore.kernel.org/lkml/[email protected]/
*fist bump*
--
Lee Jones [李琼斯]