From: Maximilian Weigand <hidden> Date: 2023-06-14 19:09:19
For certain brightness settings the Pine64 PineNote exhibits quite
visible flickering of the led backlights, leading to an unpleasant user
experience. It is understood that flickering is caused by certain power
line ripples interacting with the led driver, inherent to the
specific hardware. The lm3630a led driver is able to change the boost
converter switching frequency. Among other things, changing the boost
frequency can also greatly improve visible flickering issues.
This patchset enables dts control of two frequency modifications that the
hardware is capable of: Switch from a base frequency of 500 kHz to 1
MHz, and activate a frequency shift to 560 kHz or 1.12 MHz,
respectively.
As flickering characteristics are mainly hardware dependent, this should
warrant the inclusion of two dts entries for the lm3630a led driver to
control the boost frequency of the chip on a per-device basis.
Changes were tested on a Pine64 PineNote. The following brightness
settings were found to exhibit serious flickering without either the
frequency shift or the higher boost frequency:
echo 186 > /sys/class/backlight/backlight_warm/brightness
echo 255 > /sys/class/backlight/backlight_cool/brightness
Signed-off-by: Maximilian Weigand <redacted>
---
Maximilian Weigand (3):
backlight: lm3630a: add support for changing the boost frequency
dt-bindings: backlight: lm3630a: add entries to control boost frequency
arm64: dts: rockchip: shift boost frequency for rk3566-pinenote backlight
.../bindings/leds/backlight/lm3630a-backlight.yaml | 12 ++++++++++++
arch/arm64/boot/dts/rockchip/rk3566-pinenote.dtsi | 1 +
drivers/video/backlight/lm3630a_bl.c | 9 ++++++++-
include/linux/platform_data/lm3630a_bl.h | 5 +++++
4 files changed, 26 insertions(+), 1 deletion(-)
---
base-commit: 858fd168a95c5b9669aac8db6c14a9aeab446375
change-id: 20230602-lm3630a_boost_frequency-bae9656ec759
Best regards,
--
Maximilian Weigand [off-list ref]
From: Maximilian Weigand <hidden> Date: 2023-06-14 19:09:26
From: Maximilian Weigand <redacted>
The led driver supports changing the switching frequency of the boost
converter by two means: the base switching frequency can be changed from
500 kHz to 1 MHz, and a frequency shift can be activated, leading to
switching frequencies of 560 kHz or 1.12 Mhz, respectively.
Add this functionality to the led driver by introducing two dts entries
that control the boost frequency (500 kHz by default) and the frequency
shift (no shift by default).
Signed-off-by: Maximilian Weigand <redacted>
---
drivers/video/backlight/lm3630a_bl.c | 9 ++++++++-
include/linux/platform_data/lm3630a_bl.h | 5 +++++
2 files changed, 13 insertions(+), 1 deletion(-)
@@ -92,7 +92,7 @@ static int lm3630a_chip_init(struct lm3630a_chip *pchip)/* set Cofig. register */rval|=lm3630a_update(pchip,REG_CONFIG,0x07,pdata->pwm_ctrl);/* set boost control */-rval|=lm3630a_write(pchip,REG_BOOST,0x38);+rval|=lm3630a_write(pchip,REG_BOOST,pdata->boost_ctrl);/* set current A */rval|=lm3630a_update(pchip,REG_I_A,0x1F,0x1F);/* set current B */
@@ -528,6 +528,13 @@ static int lm3630a_probe(struct i2c_client *client)pdata->ledb_max_brt=LM3630A_MAX_BRIGHTNESS;pdata->leda_init_brt=LM3630A_MAX_BRIGHTNESS;pdata->ledb_init_brt=LM3630A_MAX_BRIGHTNESS;+pdata->boost_ctrl=LM3630A_BOOST_CTRL_DEFAULT;++if(device_property_read_bool(pchip->dev,"ti,boost_frequency_shift"))+pdata->boost_ctrl|=LM3630A_BOOST_SHIFT_FREQ;++if(device_property_read_bool(pchip->dev,"ti,boost_use_1mhz"))+pdata->boost_ctrl|=LM3630A_BOOST_USE_1MHZ;rval=lm3630a_parse_node(pchip,pdata);if(rval){
From: Daniel Thompson <hidden> Date: 2023-06-26 14:39:54
On Wed, Jun 14, 2023 at 09:08:52PM +0200, Maximilian Weigand wrote:
From: Maximilian Weigand <redacted>
The led driver supports changing the switching frequency of the boost
converter by two means: the base switching frequency can be changed from
500 kHz to 1 MHz, and a frequency shift can be activated, leading to
switching frequencies of 560 kHz or 1.12 Mhz, respectively.
Add this functionality to the led driver by introducing two dts entries
that control the boost frequency (500 kHz by default) and the frequency
shift (no shift by default).
Signed-off-by: Maximilian Weigand <redacted>
From: Maximilian Weigand <hidden> Date: 2023-06-14 19:09:37
From: Maximilian Weigand <redacted>
Add 'ti,boost_use_1mhz' to switch between 500 kHz and 1 MHz boost
converter switching frequency, and add 'ti,boost_frequency_shift' to
activate a frequency shift to 560 kHz or 1.12 MHz, respectively.
Signed-off-by: Maximilian Weigand <redacted>
---
.../bindings/leds/backlight/lm3630a-backlight.yaml | 12 ++++++++++++
1 file changed, 12 insertions(+)
@@ -33,6 +33,18 @@ properties:description:GPIO to use to enable/disable the backlight (HWEN pin).maxItems:1+ti,boost_use_1mhz:+description:|+If present, change the boost converter switching frequency from the+default 500 kHz to 1 MHz. Refer to data sheet for hardware requirements.+type:boolean++ti,boost_frequency_shift:+description:|+If present, change boost converter switching frequency from 500 kHz to+560 kHz or from 1 Mhz to 1.12 Mhz, respectively.+type:boolean+required:-compatible-reg
From: Krzysztof Kozlowski <hidden> Date: 2023-06-17 10:12:33
On 14/06/2023 21:08, Maximilian Weigand wrote:
quoted hunk
From: Maximilian Weigand <redacted>
Add 'ti,boost_use_1mhz' to switch between 500 kHz and 1 MHz boost
converter switching frequency, and add 'ti,boost_frequency_shift' to
activate a frequency shift to 560 kHz or 1.12 MHz, respectively.
Signed-off-by: Maximilian Weigand <redacted>
---
.../bindings/leds/backlight/lm3630a-backlight.yaml | 12 ++++++++++++
1 file changed, 12 insertions(+)
@@ -33,6 +33,18 @@ properties:description:GPIO to use to enable/disable the backlight (HWEN pin).maxItems:1+ti,boost_use_1mhz:
No underscores in property names.
+ description: |
Do not need '|' unless you need to preserve formatting.
+ If present, change the boost converter switching frequency from the
+ default 500 kHz to 1 MHz. Refer to data sheet for hardware requirements.
+ type: boolean
+
+ ti,boost_frequency_shift:
+ description: |
+ If present, change boost converter switching frequency from 500 kHz to
+ 560 kHz or from 1 Mhz to 1.12 Mhz, respectively.
So just make it a property choosing the frequency, not bools, with
proper unit suffix.
Best regards,
Krzysztof
Am Samstag, 17. Juni 2023, 12:12:17 CEST schrieb Krzysztof Kozlowski:
On 14/06/2023 21:08, Maximilian Weigand wrote:
quoted
From: Maximilian Weigand <redacted>
Add 'ti,boost_use_1mhz' to switch between 500 kHz and 1 MHz boost
converter switching frequency, and add 'ti,boost_frequency_shift' to
activate a frequency shift to 560 kHz or 1.12 MHz, respectively.
Signed-off-by: Maximilian Weigand <redacted>
---
.../bindings/leds/backlight/lm3630a-backlight.yaml | 12 ++++++++++++
1 file changed, 12 insertions(+)
@@ -33,6 +33,18 @@ properties:description:GPIO to use to enable/disable the backlight (HWEN pin).maxItems:1+ti,boost_use_1mhz:
No underscores in property names.
quoted
+ description: |
Do not need '|' unless you need to preserve formatting.
quoted
+ If present, change the boost converter switching frequency from the
+ default 500 kHz to 1 MHz. Refer to data sheet for hardware requirements.
+ type: boolean
+
+ ti,boost_frequency_shift:
+ description: |
+ If present, change boost converter switching frequency from 500 kHz to
+ 560 kHz or from 1 Mhz to 1.12 Mhz, respectively.
So just make it a property choosing the frequency, not bools, with
proper unit suffix.
i.e.
ti,boost-frequency-hz = <x>;
with x being 500000, 560000, 1000000, 1120000
with the driver failing when the frequency is not achievable
with the two knobs of 1mhz and shift.
From: Krzysztof Kozlowski <hidden> Date: 2023-06-17 17:42:40
On 17/06/2023 18:34, Heiko Stübner wrote:
Am Samstag, 17. Juni 2023, 12:12:17 CEST schrieb Krzysztof Kozlowski:
quoted
On 14/06/2023 21:08, Maximilian Weigand wrote:
quoted
From: Maximilian Weigand <redacted>
Add 'ti,boost_use_1mhz' to switch between 500 kHz and 1 MHz boost
converter switching frequency, and add 'ti,boost_frequency_shift' to
activate a frequency shift to 560 kHz or 1.12 MHz, respectively.
Signed-off-by: Maximilian Weigand <redacted>
---
.../bindings/leds/backlight/lm3630a-backlight.yaml | 12 ++++++++++++
1 file changed, 12 insertions(+)
@@ -33,6 +33,18 @@ properties:description:GPIO to use to enable/disable the backlight (HWEN pin).maxItems:1+ti,boost_use_1mhz:
No underscores in property names.
quoted
+ description: |
Do not need '|' unless you need to preserve formatting.
quoted
+ If present, change the boost converter switching frequency from the
+ default 500 kHz to 1 MHz. Refer to data sheet for hardware requirements.
+ type: boolean
+
+ ti,boost_frequency_shift:
+ description: |
+ If present, change boost converter switching frequency from 500 kHz to
+ 560 kHz or from 1 Mhz to 1.12 Mhz, respectively.
So just make it a property choosing the frequency, not bools, with
proper unit suffix.
i.e.
ti,boost-frequency-hz = <x>;
with x being 500000, 560000, 1000000, 1120000
with the driver failing when the frequency is not achievable
with the two knobs of 1mhz and shift.
Yeah, with a default value (500000, I guess).
Best regards,
Krzysztof
From: Maximilian Weigand <hidden> Date: 2023-06-17 18:16:07
Hi,
On 17.06.23 19:42, Krzysztof Kozlowski wrote:
On 17/06/2023 18:34, Heiko Stübner wrote:
quoted
Am Samstag, 17. Juni 2023, 12:12:17 CEST schrieb Krzysztof Kozlowski:
quoted
On 14/06/2023 21:08, Maximilian Weigand wrote:
quoted
From: Maximilian Weigand <redacted>
Add 'ti,boost_use_1mhz' to switch between 500 kHz and 1 MHz boost
converter switching frequency, and add 'ti,boost_frequency_shift' to
activate a frequency shift to 560 kHz or 1.12 MHz, respectively.
Signed-off-by: Maximilian Weigand <redacted>
---
.../bindings/leds/backlight/lm3630a-backlight.yaml | 12 ++++++++++++
1 file changed, 12 insertions(+)
@@ -33,6 +33,18 @@ properties:description:GPIO to use to enable/disable the backlight (HWEN pin).maxItems:1+ti,boost_use_1mhz:
No underscores in property names.
quoted
+ description: |
Do not need '|' unless you need to preserve formatting.
quoted
+ If present, change the boost converter switching frequency from the
+ default 500 kHz to 1 MHz. Refer to data sheet for hardware requirements.
+ type: boolean
+
+ ti,boost_frequency_shift:
+ description: |
+ If present, change boost converter switching frequency from 500 kHz to
+ 560 kHz or from 1 Mhz to 1.12 Mhz, respectively.
So just make it a property choosing the frequency, not bools, with
proper unit suffix.
i.e.
ti,boost-frequency-hz = <x>;
with x being 500000, 560000, 1000000, 1120000
with the driver failing when the frequency is not achievable
with the two knobs of 1mhz and shift.
Yeah, with a default value (500000, I guess).
Thanks for the feedback, this is quite obviously the better solution! I
will rework the submission accordingly.
Best regards
Maximilian
From: Maximilian Weigand <hidden> Date: 2023-06-14 19:09:41
From: Maximilian Weigand <redacted>
The PineNote exhibits visible flickering of its backlight for certain
brightness settings. Alleviate this by enabling a frequency shift from
500 kHz to 560 kHz for the boost converter of the led driver.
Signed-off-by: Maximilian Weigand <redacted>
---
arch/arm64/boot/dts/rockchip/rk3566-pinenote.dtsi | 1 +
1 file changed, 1 insertion(+)