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* [PATCH v7] drm/dp: clamp PWM bit count to advertised MIN and MAX capabilities
@ 2025-08-14 14:16 Neil Armstrong
  2025-08-14 19:55 ` Christopher Obbard
  2025-08-15 22:11 ` Dmitry Baryshkov
  0 siblings, 2 replies; 3+ messages in thread
From: Neil Armstrong @ 2025-08-14 14:16 UTC (permalink / raw)
  To: Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, David Airlie,
	Simona Vetter
  Cc: dri-devel, linux-kernel, johan, dmitry.baryshkov, linux-arm-msm,
	Christopher Obbard, Rui Miguel Silva, Neil Armstrong

From: Christopher Obbard <christopher.obbard@linaro.org>

According to the eDP specification (VESA Embedded DisplayPort Standard
v1.4b, Section 3.3.10.2), if the value of DP_EDP_PWMGEN_BIT_COUNT is
less than DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, the sink is required to use
the MIN value as the effective PWM bit count.

This commit updates the logic to clamp the reported
DP_EDP_PWMGEN_BIT_COUNT to the range defined by _CAP_MIN and _CAP_MAX.

As part of this change, the behavior is modified such that reading both
_CAP_MIN and _CAP_MAX registers is now required to succeed, otherwise
bl->max value could end up being not set although
drm_edp_backlight_probe_max() returned success.

This ensures correct handling of eDP panels that report a zero PWM
bit count but still provide valid non-zero MIN and MAX capability
values. Without this clamping, brightness values may be interpreted
incorrectly, leading to a dim or non-functional backlight.

For example, the Samsung ATNA40YK20 OLED panel used in the Lenovo
ThinkPad T14s Gen6 (Snapdragon) reports a PWM bit count of 0, but
supports AUX backlight control and declares a valid 11-bit range.
Clamping ensures brightness scaling works as intended on such panels.

Co-developed-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Christopher Obbard <christopher.obbard@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
---
Changes in v7:
- Take in account invalid bit_count
- Write bit_count back if clamped within BIT_COUNT_CAP_MIN & BIT_COUNT_CAP_MAX 
- Link to v6: https://lore.kernel.org/all/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v6-1-84ad1cd1078a@linaro.org 

Changes in v6:
- Update commit message around chaning reading PWMGEN_BIT_COUNT_CAP_MIN
  and _CAP_MAX to be required.
- Link to v5: https://lore.kernel.org/r/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v5-1-25083d9732fc@linaro.org

Changes in v5:
- Correctly check return value when reading PWMGEN_BIT_COUNT_CAP_MIN
  and _CAP_MAX.
- Link to v4: https://lore.kernel.org/r/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v4-1-85ef0991bdf8@linaro.org

Changes in v4:
- Remove unrelated whitespace changes.
- Remove unrelated commit change.
- Add note to commit message about changing read of PWMGEN_BIT_COUNT_CAP_MIN
  and _CAP__MAX from optional to required.
- Link to v3: https://lore.kernel.org/r/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v3-1-156801d97a8a@linaro.org

Changes in v3:
- Properly rebase patch on top of latest version of drm-misc-next.
- Make patch more generic by clamping PWM bit count to advertised MIN
  and MAX capabilities (suggested by Dmitry).
- Link to v2: https://lore.kernel.org/r/20250327-wip-obbardc-qcom-t14s-oled-panel-brightness-v2-1-16dc3ee00276@linaro.org

Changes in v2:
- Split backlight brightness patch from T14s OLED enablement series.
- Use PWMGEN_CAP_MIN rather than MAX (Dmitry).
- Rework commit message to reference eDP spec.
- Rebase on drm-misc-next.
- Link to v1: https://lore.kernel.org/all/20250325-wip-obbardc-qcom-t14s-oled-panel-v2-4-e9bc7c9d30cc@linaro.org/
---
 drivers/gpu/drm/display/drm_dp_helper.c | 68 ++++++++++++++++++++++++---------
 1 file changed, 49 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
index 1ecc3df7e3167d13636e194c4aab44ee8979aa11..011a493f06d4871074832ec954a05697103466b2 100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -29,6 +29,7 @@
 #include <linux/init.h>
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
+#include <linux/minmax.h>
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>
@@ -4126,22 +4127,61 @@ drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct drm_edp_backlight_inf
 {
 	int fxp, fxp_min, fxp_max, fxp_actual, f = 1;
 	int ret;
-	u8 pn, pn_min, pn_max;
+	u8 pn, pn_min, pn_max, bit_count;
 
 	if (!bl->aux_set)
 		return 0;
 
-	ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT, &pn);
+	ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT, &bit_count);
 	if (ret < 0) {
 		drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap: %d\n",
 			    aux->name, ret);
 		return -ENODEV;
 	}
 
-	pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+	bit_count &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+
+	ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min);
+	if (ret < 0) {
+		drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap min: %d\n",
+			    aux->name, ret);
+		return -ENODEV;
+	}
+	pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+
+	ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max);
+	if (ret < 0) {
+		drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap max: %d\n",
+			    aux->name, ret);
+		return -ENODEV;
+	}
+	pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+
+	if (unlikely(pn_min > pn_max)) {
+		drm_dbg_kms(aux->drm_dev, "%s: Invalid pwmgen bit count cap min/max returned: %d %d\n",
+			    aux->name, pn_min, pn_max);
+		return -EINVAL;
+	}
+
+	/*
+	 * Per VESA eDP Spec v1.4b, section 3.3.10.2:
+	 * If DP_EDP_PWMGEN_BIT_COUNT is less than DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN,
+	 * the sink must use the MIN value as the effective PWM bit count.
+	 * Clamp the reported value to the [MIN, MAX] capability range to ensure
+	 * correct brightness scaling on compliant eDP panels.
+	 * Only enable this logic if the [MIN, MAX] range is valid in regard to Spec.
+	 */
+	pn = bit_count;
+	if (bit_count < pn_min)
+		pn = clamp(bit_count, pn_min, pn_max);
+
 	bl->max = (1 << pn) - 1;
-	if (!driver_pwm_freq_hz)
+	if (!driver_pwm_freq_hz) {
+		if (pn != bit_count)
+			goto bit_count_write_back;
+
 		return 0;
+	}
 
 	/*
 	 * Set PWM Frequency divider to match desired frequency provided by the driver.
@@ -4165,21 +4205,6 @@ drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct drm_edp_backlight_inf
 	 * - FxP is within 25% of desired value.
 	 *   Note: 25% is arbitrary value and may need some tweak.
 	 */
-	ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min);
-	if (ret < 0) {
-		drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap min: %d\n",
-			    aux->name, ret);
-		return 0;
-	}
-	ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max);
-	if (ret < 0) {
-		drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap max: %d\n",
-			    aux->name, ret);
-		return 0;
-	}
-	pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
-	pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
-
 	/* Ensure frequency is within 25% of desired value */
 	fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4);
 	fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4);
@@ -4197,12 +4222,17 @@ drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct drm_edp_backlight_inf
 			break;
 	}
 
+bit_count_write_back:
 	ret = drm_dp_dpcd_write_byte(aux, DP_EDP_PWMGEN_BIT_COUNT, pn);
 	if (ret < 0) {
 		drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux pwmgen bit count: %d\n",
 			    aux->name, ret);
 		return 0;
 	}
+
+	if (!driver_pwm_freq_hz)
+		return 0;
+
 	bl->pwmgen_bit_count = pn;
 	bl->max = (1 << pn) - 1;
 

---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250724-topic-x1e80100-t14s-oled-dp-brightness-0190e5201d02

Best regards,
-- 
Neil Armstrong <neil.armstrong@linaro.org>


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [PATCH v7] drm/dp: clamp PWM bit count to advertised MIN and MAX capabilities
  2025-08-14 14:16 [PATCH v7] drm/dp: clamp PWM bit count to advertised MIN and MAX capabilities Neil Armstrong
@ 2025-08-14 19:55 ` Christopher Obbard
  2025-08-15 22:11 ` Dmitry Baryshkov
  1 sibling, 0 replies; 3+ messages in thread
From: Christopher Obbard @ 2025-08-14 19:55 UTC (permalink / raw)
  To: Neil Armstrong
  Cc: Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, David Airlie,
	Simona Vetter, dri-devel, linux-kernel, johan, dmitry.baryshkov,
	linux-arm-msm, Rui Miguel Silva

Hi Neil,

On Thu, 14 Aug 2025 at 15:16, Neil Armstrong <neil.armstrong@linaro.org> wrote:
>
> From: Christopher Obbard <christopher.obbard@linaro.org>
>
> According to the eDP specification (VESA Embedded DisplayPort Standard
> v1.4b, Section 3.3.10.2), if the value of DP_EDP_PWMGEN_BIT_COUNT is
> less than DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, the sink is required to use
> the MIN value as the effective PWM bit count.
>
> This commit updates the logic to clamp the reported
> DP_EDP_PWMGEN_BIT_COUNT to the range defined by _CAP_MIN and _CAP_MAX.
>
> As part of this change, the behavior is modified such that reading both
> _CAP_MIN and _CAP_MAX registers is now required to succeed, otherwise
> bl->max value could end up being not set although
> drm_edp_backlight_probe_max() returned success.
>
> This ensures correct handling of eDP panels that report a zero PWM
> bit count but still provide valid non-zero MIN and MAX capability
> values. Without this clamping, brightness values may be interpreted
> incorrectly, leading to a dim or non-functional backlight.
>
> For example, the Samsung ATNA40YK20 OLED panel used in the Lenovo
> ThinkPad T14s Gen6 (Snapdragon) reports a PWM bit count of 0, but
> supports AUX backlight control and declares a valid 11-bit range.
> Clamping ensures brightness scaling works as intended on such panels.
>
> Co-developed-by: Rui Miguel Silva <rui.silva@linaro.org>
> Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
> Signed-off-by: Christopher Obbard <christopher.obbard@linaro.org>
> Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

Thank you for taking this patch over. I guess there is no need to add
my tags; but here they are anyway:

Tested-by: Christopher Obbard <christopher.obbard@linaro.org>
Reviewed-by: Christopher Obbard <christopher.obbard@linaro.org>

> ---
> Changes in v7:
> - Take in account invalid bit_count
> - Write bit_count back if clamped within BIT_COUNT_CAP_MIN & BIT_COUNT_CAP_MAX
> - Link to v6: https://lore.kernel.org/all/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v6-1-84ad1cd1078a@linaro.org
>
> Changes in v6:
> - Update commit message around chaning reading PWMGEN_BIT_COUNT_CAP_MIN
>   and _CAP_MAX to be required.
> - Link to v5: https://lore.kernel.org/r/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v5-1-25083d9732fc@linaro.org
>
> Changes in v5:
> - Correctly check return value when reading PWMGEN_BIT_COUNT_CAP_MIN
>   and _CAP_MAX.
> - Link to v4: https://lore.kernel.org/r/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v4-1-85ef0991bdf8@linaro.org
>
> Changes in v4:
> - Remove unrelated whitespace changes.
> - Remove unrelated commit change.
> - Add note to commit message about changing read of PWMGEN_BIT_COUNT_CAP_MIN
>   and _CAP__MAX from optional to required.
> - Link to v3: https://lore.kernel.org/r/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v3-1-156801d97a8a@linaro.org
>
> Changes in v3:
> - Properly rebase patch on top of latest version of drm-misc-next.
> - Make patch more generic by clamping PWM bit count to advertised MIN
>   and MAX capabilities (suggested by Dmitry).
> - Link to v2: https://lore.kernel.org/r/20250327-wip-obbardc-qcom-t14s-oled-panel-brightness-v2-1-16dc3ee00276@linaro.org
>
> Changes in v2:
> - Split backlight brightness patch from T14s OLED enablement series.
> - Use PWMGEN_CAP_MIN rather than MAX (Dmitry).
> - Rework commit message to reference eDP spec.
> - Rebase on drm-misc-next.
> - Link to v1: https://lore.kernel.org/all/20250325-wip-obbardc-qcom-t14s-oled-panel-v2-4-e9bc7c9d30cc@linaro.org/
> ---
>  drivers/gpu/drm/display/drm_dp_helper.c | 68 ++++++++++++++++++++++++---------
>  1 file changed, 49 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> index 1ecc3df7e3167d13636e194c4aab44ee8979aa11..011a493f06d4871074832ec954a05697103466b2 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -29,6 +29,7 @@
>  #include <linux/init.h>
>  #include <linux/iopoll.h>
>  #include <linux/kernel.h>
> +#include <linux/minmax.h>
>  #include <linux/module.h>
>  #include <linux/sched.h>
>  #include <linux/seq_file.h>
> @@ -4126,22 +4127,61 @@ drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct drm_edp_backlight_inf
>  {
>         int fxp, fxp_min, fxp_max, fxp_actual, f = 1;
>         int ret;
> -       u8 pn, pn_min, pn_max;
> +       u8 pn, pn_min, pn_max, bit_count;
>
>         if (!bl->aux_set)
>                 return 0;
>
> -       ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT, &pn);
> +       ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT, &bit_count);
>         if (ret < 0) {
>                 drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap: %d\n",
>                             aux->name, ret);
>                 return -ENODEV;
>         }
>
> -       pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> +       bit_count &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> +
> +       ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min);
> +       if (ret < 0) {
> +               drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap min: %d\n",
> +                           aux->name, ret);
> +               return -ENODEV;
> +       }
> +       pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> +
> +       ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max);
> +       if (ret < 0) {
> +               drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap max: %d\n",
> +                           aux->name, ret);
> +               return -ENODEV;
> +       }
> +       pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> +
> +       if (unlikely(pn_min > pn_max)) {
> +               drm_dbg_kms(aux->drm_dev, "%s: Invalid pwmgen bit count cap min/max returned: %d %d\n",
> +                           aux->name, pn_min, pn_max);
> +               return -EINVAL;
> +       }
> +
> +       /*
> +        * Per VESA eDP Spec v1.4b, section 3.3.10.2:
> +        * If DP_EDP_PWMGEN_BIT_COUNT is less than DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN,
> +        * the sink must use the MIN value as the effective PWM bit count.
> +        * Clamp the reported value to the [MIN, MAX] capability range to ensure
> +        * correct brightness scaling on compliant eDP panels.
> +        * Only enable this logic if the [MIN, MAX] range is valid in regard to Spec.
> +        */
> +       pn = bit_count;
> +       if (bit_count < pn_min)
> +               pn = clamp(bit_count, pn_min, pn_max);
> +
>         bl->max = (1 << pn) - 1;
> -       if (!driver_pwm_freq_hz)
> +       if (!driver_pwm_freq_hz) {
> +               if (pn != bit_count)
> +                       goto bit_count_write_back;
> +
>                 return 0;
> +       }
>
>         /*
>          * Set PWM Frequency divider to match desired frequency provided by the driver.
> @@ -4165,21 +4205,6 @@ drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct drm_edp_backlight_inf
>          * - FxP is within 25% of desired value.
>          *   Note: 25% is arbitrary value and may need some tweak.
>          */
> -       ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min);
> -       if (ret < 0) {
> -               drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap min: %d\n",
> -                           aux->name, ret);
> -               return 0;
> -       }
> -       ret = drm_dp_dpcd_read_byte(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max);
> -       if (ret < 0) {
> -               drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap max: %d\n",
> -                           aux->name, ret);
> -               return 0;
> -       }
> -       pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> -       pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> -
>         /* Ensure frequency is within 25% of desired value */
>         fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4);
>         fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4);
> @@ -4197,12 +4222,17 @@ drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct drm_edp_backlight_inf
>                         break;
>         }
>
> +bit_count_write_back:
>         ret = drm_dp_dpcd_write_byte(aux, DP_EDP_PWMGEN_BIT_COUNT, pn);
>         if (ret < 0) {
>                 drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux pwmgen bit count: %d\n",
>                             aux->name, ret);
>                 return 0;
>         }
> +
> +       if (!driver_pwm_freq_hz)
> +               return 0;
> +
>         bl->pwmgen_bit_count = pn;
>         bl->max = (1 << pn) - 1;
>
>
> ---
> base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
> change-id: 20250724-topic-x1e80100-t14s-oled-dp-brightness-0190e5201d02
>
> Best regards,
> --
> Neil Armstrong <neil.armstrong@linaro.org>
>

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH v7] drm/dp: clamp PWM bit count to advertised MIN and MAX capabilities
  2025-08-14 14:16 [PATCH v7] drm/dp: clamp PWM bit count to advertised MIN and MAX capabilities Neil Armstrong
  2025-08-14 19:55 ` Christopher Obbard
@ 2025-08-15 22:11 ` Dmitry Baryshkov
  1 sibling, 0 replies; 3+ messages in thread
From: Dmitry Baryshkov @ 2025-08-15 22:11 UTC (permalink / raw)
  To: Neil Armstrong
  Cc: Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, David Airlie,
	Simona Vetter, dri-devel, linux-kernel, johan, linux-arm-msm,
	Christopher Obbard, Rui Miguel Silva

On Thu, Aug 14, 2025 at 04:16:09PM +0200, Neil Armstrong wrote:
> From: Christopher Obbard <christopher.obbard@linaro.org>
> 
> According to the eDP specification (VESA Embedded DisplayPort Standard
> v1.4b, Section 3.3.10.2), if the value of DP_EDP_PWMGEN_BIT_COUNT is
> less than DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, the sink is required to use
> the MIN value as the effective PWM bit count.
> 
> This commit updates the logic to clamp the reported
> DP_EDP_PWMGEN_BIT_COUNT to the range defined by _CAP_MIN and _CAP_MAX.
> 
> As part of this change, the behavior is modified such that reading both
> _CAP_MIN and _CAP_MAX registers is now required to succeed, otherwise
> bl->max value could end up being not set although
> drm_edp_backlight_probe_max() returned success.
> 
> This ensures correct handling of eDP panels that report a zero PWM
> bit count but still provide valid non-zero MIN and MAX capability
> values. Without this clamping, brightness values may be interpreted
> incorrectly, leading to a dim or non-functional backlight.
> 
> For example, the Samsung ATNA40YK20 OLED panel used in the Lenovo
> ThinkPad T14s Gen6 (Snapdragon) reports a PWM bit count of 0, but
> supports AUX backlight control and declares a valid 11-bit range.
> Clamping ensures brightness scaling works as intended on such panels.
> 
> Co-developed-by: Rui Miguel Silva <rui.silva@linaro.org>
> Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
> Signed-off-by: Christopher Obbard <christopher.obbard@linaro.org>
> Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
> ---
> Changes in v7:
> - Take in account invalid bit_count
> - Write bit_count back if clamped within BIT_COUNT_CAP_MIN & BIT_COUNT_CAP_MAX 
> - Link to v6: https://lore.kernel.org/all/20250330-wip-obbardc-qcom-t14s-oled-panel-brightness-v6-1-84ad1cd1078a@linaro.org 
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>


-- 
With best wishes
Dmitry

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2025-08-14 14:16 [PATCH v7] drm/dp: clamp PWM bit count to advertised MIN and MAX capabilities Neil Armstrong
2025-08-14 19:55 ` Christopher Obbard
2025-08-15 22:11 ` Dmitry Baryshkov

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