Currently, upowerd is unable to turn off the battery preservation mode[1]
on Qualcomm laptops, because it does that by setting the start threshold to
zero and the driver returns an error:

pmic_glink.power-supply.0: charge control start threshold exceed range: [50 - 95]

Kernel documentation says the end threshold must be clamped[2] but does
not say anything about the start threshold.

In this proposal I've special-cased start==0 to actually disable the
functionality via the enable bit, and otherwise made both start and
end thresholds be clamped to the acceptable range. Hopefully that's
fine? Or should the [1 - 49] range for start actually be rejected?

[1]: https://gitlab.freedesktop.org/upower/upower/-/issues/327
[2]: https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-power

Thanks,
~val

Val Packett (2):
  power: supply: qcom_battmgr: clamp charge control thresholds
  power: supply: qcom_battmgr: support disabling charge control

 drivers/power/supply/qcom_battmgr.c | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

-- 
2.51.0

On 10/13/2025 7:32 AM, Val Packett wrote:
> Currently, upowerd is unable to turn off the battery preservation mode[1]
> on Qualcomm laptops, because it does that by setting the start threshold to
> zero and the driver returns an error:
>
> pmic_glink.power-supply.0: charge control start threshold exceed range: [50 - 95]
>
> Kernel documentation says the end threshold must be clamped[2] but does
> not say anything about the start threshold.
>
> In this proposal I've special-cased start==0 to actually disable the
> functionality via the enable bit, and otherwise made both start and
> end thresholds be clamped to the acceptable range. Hopefully that's
> fine?
It is fine to clamping the threshold to the acceptable range. Thank you 
for making the changes.
> Or should the [1 - 49] range for start actually be rejected?
The minimum charging start threshold was set to 50 to improve user 
experience. If the threshold is too low and the system keeps drawing 
power from the battery frequently due to a large system load and a weak 
charger, the laptop will only begin charging when the battery level 
falls below that threshold. If the user disconnects the charger at that 
time, then the device would be only having a battery below 50%. Setting 
the threshold at 50 ensures the battery always stays above 50%.
> [1]: https://gitlab.freedesktop.org/upower/upower/-/issues/327
> [2]: https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-power
>
> Thanks,
> ~val
>
> Val Packett (2):
>    power: supply: qcom_battmgr: clamp charge control thresholds
>    power: supply: qcom_battmgr: support disabling charge control
>
>   drivers/power/supply/qcom_battmgr.c | 26 ++++++++++----------------
>   1 file changed, 10 insertions(+), 16 deletions(-)
>

On 11/17/25 6:12 AM, Fenglin Wu wrote:
> 
> On 10/13/2025 7:32 AM, Val Packett wrote:
>> Currently, upowerd is unable to turn off the battery preservation mode[1]
>> on Qualcomm laptops, because it does that by setting the start threshold to
>> zero and the driver returns an error:
>>
>> pmic_glink.power-supply.0: charge control start threshold exceed range: [50 - 95]
>>
>> Kernel documentation says the end threshold must be clamped[2] but does
>> not say anything about the start threshold.
>>
>> In this proposal I've special-cased start==0 to actually disable the
>> functionality via the enable bit, and otherwise made both start and
>> end thresholds be clamped to the acceptable range. Hopefully that's
>> fine?
> It is fine to clamping the threshold to the acceptable range. Thank you for making the changes.
>> Or should the [1 - 49] range for start actually be rejected?
> The minimum charging start threshold was set to 50 to improve user experience. If the threshold is too low and the system keeps drawing power from the battery frequently due to a large system load and a weak charger, the laptop will only begin charging when the battery level falls below that threshold. If the user disconnects the charger at that time, then the device would be only having a battery below 50%. Setting the threshold at 50 ensures the battery always stays above 50%.

So can we set it lower?

Such decisions are best deferred to userspace and/or the user, which can
limit what the kernel exposes as necessary/deemed useful

Konrad

On 11/17/2025 8:45 PM, Konrad Dybcio wrote:
> On 11/17/25 6:12 AM, Fenglin Wu wrote:
>> On 10/13/2025 7:32 AM, Val Packett wrote:
>>> Currently, upowerd is unable to turn off the battery preservation mode[1]
>>> on Qualcomm laptops, because it does that by setting the start threshold to
>>> zero and the driver returns an error:
>>>
>>> pmic_glink.power-supply.0: charge control start threshold exceed range: [50 - 95]
>>>
>>> Kernel documentation says the end threshold must be clamped[2] but does
>>> not say anything about the start threshold.
>>>
>>> In this proposal I've special-cased start==0 to actually disable the
>>> functionality via the enable bit, and otherwise made both start and
>>> end thresholds be clamped to the acceptable range. Hopefully that's
>>> fine?
>> It is fine to clamping the threshold to the acceptable range. Thank you for making the changes.
>>> Or should the [1 - 49] range for start actually be rejected?
>> The minimum charging start threshold was set to 50 to improve user experience. If the threshold is too low and the system keeps drawing power from the battery frequently due to a large system load and a weak charger, the laptop will only begin charging when the battery level falls below that threshold. If the user disconnects the charger at that time, then the device would be only having a battery below 50%. Setting the threshold at 50 ensures the battery always stays above 50%.
> So can we set it lower?
>
> Such decisions are best deferred to userspace and/or the user, which can
> limit what the kernel exposes as necessary/deemed useful
>
> Konrad

Yes, it can be set to a lower value.

However, I am still having concerns that the inappropriate start and end 
threshold settings would cause a very bad user experience if they are 
misused, since these thresholds are stored in nvmem and they won't be 
reset until battery is unplugged or completely drained. For example, if 
someone intentionally sets the start threshold to 1 and end threshold to 
6, and if the laptop was shutdown with a battery SoC less than the end 
threshold, I am not sure if <6% percent battery level would be good 
enough to boot up the laptop successfully, if it is not, then the laptop 
may not have chance to charge up until you hot plug the battery.

Also, from battery management firmware point of view, the charge control 
feature was mainly designed for battery health management, to slow the 
aging of Li-ion battery by preventing it from being frequently charged 
to full state. Having a too low minimum start threshold setting won't 
help anything on that.

Thanks

Fenglin

On 11/18/25 3:29 AM, Fenglin Wu wrote:
> 
> On 11/17/2025 8:45 PM, Konrad Dybcio wrote:
>> On 11/17/25 6:12 AM, Fenglin Wu wrote:
>>> On 10/13/2025 7:32 AM, Val Packett wrote:
>>>> Currently, upowerd is unable to turn off the battery preservation mode[1]
>>>> on Qualcomm laptops, because it does that by setting the start threshold to
>>>> zero and the driver returns an error:
>>>>
>>>> pmic_glink.power-supply.0: charge control start threshold exceed range: [50 - 95]
>>>>
>>>> Kernel documentation says the end threshold must be clamped[2] but does
>>>> not say anything about the start threshold.
>>>>
>>>> In this proposal I've special-cased start==0 to actually disable the
>>>> functionality via the enable bit, and otherwise made both start and
>>>> end thresholds be clamped to the acceptable range. Hopefully that's
>>>> fine?
>>> It is fine to clamping the threshold to the acceptable range. Thank you for making the changes.
>>>> Or should the [1 - 49] range for start actually be rejected?
>>> The minimum charging start threshold was set to 50 to improve user experience. If the threshold is too low and the system keeps drawing power from the battery frequently due to a large system load and a weak charger, the laptop will only begin charging when the battery level falls below that threshold. If the user disconnects the charger at that time, then the device would be only having a battery below 50%. Setting the threshold at 50 ensures the battery always stays above 50%.
>> So can we set it lower?
>>
>> Such decisions are best deferred to userspace and/or the user, which can
>> limit what the kernel exposes as necessary/deemed useful
>>
>> Konrad
> 
> Yes, it can be set to a lower value.
> 
> However, I am still having concerns that the inappropriate start and end threshold settings would cause a very bad user experience if they are misused, since these thresholds are stored in nvmem and they won't be reset until battery is unplugged or completely drained. For example, if someone intentionally sets the start threshold to 1 and end threshold to 6, and if the laptop was shutdown with a battery SoC less than the end threshold, I am not sure if <6% percent battery level would be good enough to boot up the laptop successfully, if it is not, then the laptop may not have chance to charge up until you hot plug the battery.
> 
> Also, from battery management firmware point of view, the charge control feature was mainly designed for battery health management, to slow the aging of Li-ion battery by preventing it from being frequently charged to full state. Having a too low minimum start threshold setting won't help anything on that.

Perhaps 50 makes sense then. Maybe we can encode this reasoning somewhere
in the power supply API docs so it's harder to make the "can't boot anymore"
mistake you mentioned

Konrad

On Sun, 12 Oct 2025 20:32:17 -0300, Val Packett wrote:
> Currently, upowerd is unable to turn off the battery preservation mode[1]
> on Qualcomm laptops, because it does that by setting the start threshold to
> zero and the driver returns an error:
> 
> pmic_glink.power-supply.0: charge control start threshold exceed range: [50 - 95]
> 
> Kernel documentation says the end threshold must be clamped[2] but does
> not say anything about the start threshold.
> 
> [...]

Applied, thanks!

[1/2] power: supply: qcom_battmgr: clamp charge control thresholds
      commit: 8809980fdc8a86070667032fa4005ee83f1c62f3
[2/2] power: supply: qcom_battmgr: support disabling charge control
      commit: 446fcf494691da4e685923e5fad02b163955fc0e

Best regards,
-- 
Sebastian Reichel <sebastian.reichel@collabora.com>

On 11/2/25 9:48 PM, Sebastian Reichel wrote:

> On Sun, 12 Oct 2025 20:32:17 -0300, Val Packett wrote:
>> Currently, upowerd is unable to turn off the battery preservation mode[1]
>> on Qualcomm laptops, because it does that by setting the start threshold to
>> zero and the driver returns an error:
>>
>> pmic_glink.power-supply.0: charge control start threshold exceed range: [50 - 95]
>>
>> Kernel documentation says the end threshold must be clamped[2] but does
>> not say anything about the start threshold.
>>
>> [...]
> Applied, thanks!
>
> [1/2] power: supply: qcom_battmgr: clamp charge control thresholds
>        commit: 8809980fdc8a86070667032fa4005ee83f1c62f3
> [2/2] power: supply: qcom_battmgr: support disabling charge control
>        commit: 446fcf494691da4e685923e5fad02b163955fc0e


Woahh.. please revert the second one.

I'm sorry, I thought this was discussed here but apparently it was only 
on IRC and I must've assumed that the patches weren't going anywhere 
because of the lack of R-b..

The disable bit was acting rather strange after all, we'd need more work 
to figure out if that's even possible. Let's leave it at the clamp only.

~val

Hi,

On Mon, Nov 03, 2025 at 12:46:13AM -0300, Val Packett wrote:
> On 11/2/25 9:48 PM, Sebastian Reichel wrote:
> 
> > On Sun, 12 Oct 2025 20:32:17 -0300, Val Packett wrote:
> > > Currently, upowerd is unable to turn off the battery preservation mode[1]
> > > on Qualcomm laptops, because it does that by setting the start threshold to
> > > zero and the driver returns an error:
> > > 
> > > pmic_glink.power-supply.0: charge control start threshold exceed range: [50 - 95]
> > > 
> > > Kernel documentation says the end threshold must be clamped[2] but does
> > > not say anything about the start threshold.
> > > 
> > > [...]
> > Applied, thanks!
> > 
> > [1/2] power: supply: qcom_battmgr: clamp charge control thresholds
> >        commit: 8809980fdc8a86070667032fa4005ee83f1c62f3
> > [2/2] power: supply: qcom_battmgr: support disabling charge control
> >        commit: 446fcf494691da4e685923e5fad02b163955fc0e
> 
> 
> Woahh.. please revert the second one.
> 
> I'm sorry, I thought this was discussed here but apparently it was only on
> IRC and I must've assumed that the patches weren't going anywhere because of
> the lack of R-b..
> 
> The disable bit was acting rather strange after all, we'd need more work to
> figure out if that's even possible. Let's leave it at the clamp only.

DONE.

Greetings,

-- Sebastian