Previously 1 is unconditionally taken as current brightness value. This causes problems since it's required to restore brightness settings on resumption, and a value that doesn't match EC's state before suspension will cause surprising changes of screen brightness.
Let's get brightness from EC and take it as the current brightness on probe of the laptop driver to avoid the surprising behavior. Tested on TongFang L860-T2 3A5000 laptop.
Cc: stable@vger.kernel.org Fixes: 6246ed09111f ("LoongArch: Add ACPI-based generic laptop driver") Signed-off-by: Yao Zi ziyao@disroot.org --- drivers/platform/loongarch/loongson-laptop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/loongarch/loongson-laptop.c b/drivers/platform/loongarch/loongson-laptop.c index 99203584949d..828bd62e3596 100644 --- a/drivers/platform/loongarch/loongson-laptop.c +++ b/drivers/platform/loongarch/loongson-laptop.c @@ -392,7 +392,7 @@ static int laptop_backlight_register(void) if (!acpi_evalf(hotkey_handle, &status, "ECLL", "d")) return -EIO;
- props.brightness = 1; + props.brightness = ec_get_brightness(); props.max_brightness = status; props.type = BACKLIGHT_PLATFORM;
On Sat, May 31, 2025 at 7:39 PM Yao Zi ziyao@disroot.org wrote:
Previously 1 is unconditionally taken as current brightness value. This causes problems since it's required to restore brightness settings on resumption, and a value that doesn't match EC's state before suspension will cause surprising changes of screen brightness.
laptop_backlight_register() isn't called at resuming, so I think your problem has nothing to do with suspend (S3).
But there is really a problem about hibernation (S4): the brightness is 1 during booting, but when switching to the target kernel, the brightness may jump to the old value.
If the above case is what you meet, please update the commit message.
Huacai
Let's get brightness from EC and take it as the current brightness on probe of the laptop driver to avoid the surprising behavior. Tested on TongFang L860-T2 3A5000 laptop.
Cc: stable@vger.kernel.org Fixes: 6246ed09111f ("LoongArch: Add ACPI-based generic laptop driver") Signed-off-by: Yao Zi ziyao@disroot.org
drivers/platform/loongarch/loongson-laptop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/loongarch/loongson-laptop.c b/drivers/platform/loongarch/loongson-laptop.c index 99203584949d..828bd62e3596 100644 --- a/drivers/platform/loongarch/loongson-laptop.c +++ b/drivers/platform/loongarch/loongson-laptop.c @@ -392,7 +392,7 @@ static int laptop_backlight_register(void) if (!acpi_evalf(hotkey_handle, &status, "ECLL", "d")) return -EIO;
props.brightness = 1;
props.brightness = ec_get_brightness(); props.max_brightness = status; props.type = BACKLIGHT_PLATFORM;-- 2.49.0
On Tue, Jun 03, 2025 at 12:11:48PM +0800, Huacai Chen wrote:
On Sat, May 31, 2025 at 7:39 PM Yao Zi ziyao@disroot.org wrote:
Previously 1 is unconditionally taken as current brightness value. This causes problems since it's required to restore brightness settings on resumption, and a value that doesn't match EC's state before suspension will cause surprising changes of screen brightness.
laptop_backlight_register() isn't called at resuming, so I think your problem has nothing to do with suspend (S3).
It does have something to do with it. In loongson_hotkey_resume() which is called when leaving S3 (suspension), the brightness is restored according to props.brightness,
bd = backlight_device_get_by_type(BACKLIGHT_PLATFORM); if (bd) { loongson_laptop_backlight_update(bd) ? pr_warn("Loongson_backlight: resume brightness failed") : pr_info("Loongson_backlight: resume brightness %d\n", bd->props .brightness); }
and without this patch, props.brightness is always set to 1 when the driver probes, but actually (at least with the firmware on my laptop) the screen brightness is set to 80 instead of 1 on cold boot, IOW, a brightness value that doesn't match hardware state is set to props.brightness.
On resumption, loongson_hotkey_resume() restores the brightness settings according to props.brightness. But as the value isn't what is used by hardware before suspension. the screen brightness will look very different (1 v.s. 80) comparing to the brightness before suspension.
Some dmesg proves this as well, without this patch it says
loongson_laptop: Loongson_backlight: resume brightness 1
but before suspension, reading /sys/class/backlight/loongson3_laptop/actual_brightness yields 80.
But there is really a problem about hibernation (S4): the brightness is 1 during booting, but when switching to the target kernel, the brightness may jump to the old value.
If the above case is what you meet, please update the commit message.
Huacai
Thanks, Yao Zi
Let's get brightness from EC and take it as the current brightness on probe of the laptop driver to avoid the surprising behavior. Tested on TongFang L860-T2 3A5000 laptop.
Cc: stable@vger.kernel.org Fixes: 6246ed09111f ("LoongArch: Add ACPI-based generic laptop driver") Signed-off-by: Yao Zi ziyao@disroot.org
drivers/platform/loongarch/loongson-laptop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/loongarch/loongson-laptop.c b/drivers/platform/loongarch/loongson-laptop.c index 99203584949d..828bd62e3596 100644 --- a/drivers/platform/loongarch/loongson-laptop.c +++ b/drivers/platform/loongarch/loongson-laptop.c @@ -392,7 +392,7 @@ static int laptop_backlight_register(void) if (!acpi_evalf(hotkey_handle, &status, "ECLL", "d")) return -EIO;
props.brightness = 1;
props.brightness = ec_get_brightness(); props.max_brightness = status; props.type = BACKLIGHT_PLATFORM;-- 2.49.0
On Tue, Jun 3, 2025 at 2:44 PM Yao Zi ziyao@disroot.org wrote:
On Tue, Jun 03, 2025 at 12:11:48PM +0800, Huacai Chen wrote:
On Sat, May 31, 2025 at 7:39 PM Yao Zi ziyao@disroot.org wrote:
Previously 1 is unconditionally taken as current brightness value. This causes problems since it's required to restore brightness settings on resumption, and a value that doesn't match EC's state before suspension will cause surprising changes of screen brightness.
laptop_backlight_register() isn't called at resuming, so I think your problem has nothing to do with suspend (S3).
It does have something to do with it. In loongson_hotkey_resume() which is called when leaving S3 (suspension), the brightness is restored according to props.brightness,
bd = backlight_device_get_by_type(BACKLIGHT_PLATFORM); if (bd) { loongson_laptop_backlight_update(bd) ? pr_warn("Loongson_backlight: resume brightness failed") : pr_info("Loongson_backlight: resume brightness %d\n", bd->props.brightness); }
and without this patch, props.brightness is always set to 1 when the driver probes, but actually (at least with the firmware on my laptop) the screen brightness is set to 80 instead of 1 on cold boot, IOW, a brightness value that doesn't match hardware state is set to props.brightness.
On resumption, loongson_hotkey_resume() restores the brightness settings according to props.brightness. But as the value isn't what is used by hardware before suspension. the screen brightness will look very different (1 v.s. 80) comparing to the brightness before suspension.
Some dmesg proves this as well, without this patch it says
loongson_laptop: Loongson_backlight: resume brightness 1but before suspension, reading /sys/class/backlight/loongson3_laptop/actual_brightness yields 80.
OK, that makes sense. But the commit message can still be improved, at least replace suspension/resumption with suspend/resume. You can grep them at Documentation/power.
Huacai
But there is really a problem about hibernation (S4): the brightness is 1 during booting, but when switching to the target kernel, the brightness may jump to the old value.
If the above case is what you meet, please update the commit message.
Huacai
Thanks, Yao Zi
Let's get brightness from EC and take it as the current brightness on probe of the laptop driver to avoid the surprising behavior. Tested on TongFang L860-T2 3A5000 laptop.
Cc: stable@vger.kernel.org Fixes: 6246ed09111f ("LoongArch: Add ACPI-based generic laptop driver") Signed-off-by: Yao Zi ziyao@disroot.org
drivers/platform/loongarch/loongson-laptop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/loongarch/loongson-laptop.c b/drivers/platform/loongarch/loongson-laptop.c index 99203584949d..828bd62e3596 100644 --- a/drivers/platform/loongarch/loongson-laptop.c +++ b/drivers/platform/loongarch/loongson-laptop.c @@ -392,7 +392,7 @@ static int laptop_backlight_register(void) if (!acpi_evalf(hotkey_handle, &status, "ECLL", "d")) return -EIO;
props.brightness = 1;
props.brightness = ec_get_brightness(); props.max_brightness = status; props.type = BACKLIGHT_PLATFORM;-- 2.49.0
On Wed, Jun 04, 2025 at 09:56:20PM +0800, Huacai Chen wrote:
On Tue, Jun 3, 2025 at 2:44 PM Yao Zi ziyao@disroot.org wrote:
On Tue, Jun 03, 2025 at 12:11:48PM +0800, Huacai Chen wrote:
On Sat, May 31, 2025 at 7:39 PM Yao Zi ziyao@disroot.org wrote:
Previously 1 is unconditionally taken as current brightness value. This causes problems since it's required to restore brightness settings on resumption, and a value that doesn't match EC's state before suspension will cause surprising changes of screen brightness.
laptop_backlight_register() isn't called at resuming, so I think your problem has nothing to do with suspend (S3).
It does have something to do with it. In loongson_hotkey_resume() which is called when leaving S3 (suspension), the brightness is restored according to props.brightness,
bd = backlight_device_get_by_type(BACKLIGHT_PLATFORM); if (bd) { loongson_laptop_backlight_update(bd) ? pr_warn("Loongson_backlight: resume brightness failed") : pr_info("Loongson_backlight: resume brightness %d\n", bd->props.brightness); }
and without this patch, props.brightness is always set to 1 when the driver probes, but actually (at least with the firmware on my laptop) the screen brightness is set to 80 instead of 1 on cold boot, IOW, a brightness value that doesn't match hardware state is set to props.brightness.
On resumption, loongson_hotkey_resume() restores the brightness settings according to props.brightness. But as the value isn't what is used by hardware before suspension. the screen brightness will look very different (1 v.s. 80) comparing to the brightness before suspension.
Some dmesg proves this as well, without this patch it says
loongson_laptop: Loongson_backlight: resume brightness 1but before suspension, reading /sys/class/backlight/loongson3_laptop/actual_brightness yields 80.
OK, that makes sense. But the commit message can still be improved, at least replace suspension/resumption with suspend/resume. You can grep them at Documentation/power.
Oops, thanks for the hint. Seems suspend/resume are wider used, and I will reword the commit message in v2 :)
Huacai
Regards, Yao Zi
But there is really a problem about hibernation (S4): the brightness is 1 during booting, but when switching to the target kernel, the brightness may jump to the old value.
If the above case is what you meet, please update the commit message.
Huacai
Thanks, Yao Zi
Let's get brightness from EC and take it as the current brightness on probe of the laptop driver to avoid the surprising behavior. Tested on TongFang L860-T2 3A5000 laptop.
Cc: stable@vger.kernel.org Fixes: 6246ed09111f ("LoongArch: Add ACPI-based generic laptop driver") Signed-off-by: Yao Zi ziyao@disroot.org
drivers/platform/loongarch/loongson-laptop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/loongarch/loongson-laptop.c b/drivers/platform/loongarch/loongson-laptop.c index 99203584949d..828bd62e3596 100644 --- a/drivers/platform/loongarch/loongson-laptop.c +++ b/drivers/platform/loongarch/loongson-laptop.c @@ -392,7 +392,7 @@ static int laptop_backlight_register(void) if (!acpi_evalf(hotkey_handle, &status, "ECLL", "d")) return -EIO;
props.brightness = 1;
props.brightness = ec_get_brightness(); props.max_brightness = status; props.type = BACKLIGHT_PLATFORM;-- 2.49.0
linux-stable-mirror@lists.linaro.org
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Huacai Chen -
Yao Zi