Messages in this thread | | | Date | Thu, 27 Jun 2019 20:37:52 +0200 | From | Sebastian Reichel <> | Subject | Re: [PATCH v4 1/2] power: supply: add input power and voltage limit properties |
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Hi,
I just queued both patches. Thanks for the detailed description and documentation.
-- Sebastian
On Tue, Jun 25, 2019 at 12:04:13PM +0200, Enric Balletbo Serra wrote: > Hi Sebastian, Pavel, > > Missatge de Benson Leung <bleung@google.com> del dia dj., 23 de maig > 2019 a les 21:55: > > > > Hi Enric, > > > > On Tue, May 07, 2019 at 11:52:47AM +0200, Enric Balletbo i Serra wrote: > > > For thermal management strategy you might be interested on limit the > > > input power for a power supply. We already have current limit but > > > basically what we probably want is to limit power. So, introduce the > > > input_power_limit property. > > > > > > Although the common use case is limit the input power, in some > > > specific cases it is the voltage that is problematic (i.e some regulators > > > have different efficiencies at higher voltage resulting in more heat). > > > So introduce also the input_voltage_limit property. > > > > > > This happens in one Chromebook and is used on the Pixel C's thermal > > > management strategy to effectively limit the input power to 5V 3A when > > > the screen is on. When the screen is on, the display, the CPU, and the GPU > > > all contribute more heat to the system than while the screen is off, and > > > we made a tradeoff to throttle the charger in order to give more of the > > > thermal budget to those other components. > > > > > > So there's nothing fundamentally broken about the hardware that would > > > cause the Pixel C to malfunction if we were charging at 9V or 12V instead > > > of 5V when the screen is on, i.e. if userspace doesn't change this. > > > > > > What would happen is that you wouldn't meet Google's skin temperature > > > targets on the system if the charger was allowed to run at 9V or 12V with > > > the screen on. > > > > > > For folks hacking on Pixel Cs (which is now outside of Google's official > > > support window for Android) and customizing their own kernel and userspace > > > this would be acceptable, but we wanted to expose this feature in the > > > power supply properties because the feature does exist in the Emedded > > > Controller firmware of the Pixel C and all of Google's Chromebooks with > > > USB-C made since 2015 in case someone running an up to date kernel wanted > > > to limit the charging power for thermal or other reasons. > > > > > > This patch exposes a new property, similar to input current limit, to > > > re-configure the maximum voltage from the external supply at runtime > > > based on system-level knowledge or user input. > > > > > > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> > > > Reviewed-by: Guenter Roeck <groeck@chromium.org> > > > Acked-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com> > > > > Reviewed-by: Benson Leung <bleung@chromium.org> > > > > We're close to the merge window so I'm wondering if there are more > concerns on this patchset? > > Thanks, > ~ Enric > > > > --- > > > > > > Changes in v4: > > > - Add also input_power_limit. > > > > > > Changes in v3: > > > - Improve commit log and documentation with Benson comments. > > > > > > Changes in v2: > > > - Document the new property in ABI/testing/sysfs-class-power. > > > - Add the Reviewed-by Guenter Roeck tag. > > > > > > Documentation/ABI/testing/sysfs-class-power | 32 +++++++++++++++++++++ > > > Documentation/power/power_supply_class.txt | 4 +++ > > > drivers/power/supply/power_supply_sysfs.c | 2 ++ > > > include/linux/power_supply.h | 2 ++ > > > 4 files changed, 40 insertions(+) > > > > > > diff --git a/Documentation/ABI/testing/sysfs-class-power b/Documentation/ABI/testing/sysfs-class-power > > > index 5e23e22dce1b..962a27a1daf8 100644 > > > --- a/Documentation/ABI/testing/sysfs-class-power > > > +++ b/Documentation/ABI/testing/sysfs-class-power > > > @@ -331,10 +331,42 @@ Description: > > > supply. Normally this is configured based on the type of > > > connection made (e.g. A configured SDP should output a maximum > > > of 500mA so the input current limit is set to the same value). > > > + Use preferably input_power_limit, and for problems that can be > > > + solved using power limit use input_current_limit. > > > > > > Access: Read, Write > > > Valid values: Represented in microamps > > > > > > +What: /sys/class/power_supply/<supply_name>/input_voltage_limit > > > +Date: May 2019 > > > +Contact: linux-pm@vger.kernel.org > > > +Description: > > > + This entry configures the incoming VBUS voltage limit currently > > > + set in the supply. Normally this is configured based on > > > + system-level knowledge or user input (e.g. This is part of the > > > + Pixel C's thermal management strategy to effectively limit the > > > + input power to 5V when the screen is on to meet Google's skin > > > + temperature targets). Note that this feature should not be > > > + used for safety critical things. > > > + Use preferably input_power_limit, and for problems that can be > > > + solved using power limit use input_voltage_limit. > > > + > > > + Access: Read, Write > > > + Valid values: Represented in microvolts > > > + > > > +What: /sys/class/power_supply/<supply_name>/input_power_limit > > > +Date: May 2019 > > > +Contact: linux-pm@vger.kernel.org > > > +Description: > > > + This entry configures the incoming power limit currently set > > > + in the supply. Normally this is configured based on > > > + system-level knowledge or user input. Use preferably this > > > + feature to limit the incoming power and use current/voltage > > > + limit only for problems that can be solved using power limit. > > > + > > > + Access: Read, Write > > > + Valid values: Represented in microwatts > > > + > > > What: /sys/class/power_supply/<supply_name>/online, > > > Date: May 2007 > > > Contact: linux-pm@vger.kernel.org > > > diff --git a/Documentation/power/power_supply_class.txt b/Documentation/power/power_supply_class.txt > > > index 300d37896e51..1e3c705111db 100644 > > > --- a/Documentation/power/power_supply_class.txt > > > +++ b/Documentation/power/power_supply_class.txt > > > @@ -137,6 +137,10 @@ power supply object. > > > > > > INPUT_CURRENT_LIMIT - input current limit programmed by charger. Indicates > > > the current drawn from a charging source. > > > +INPUT_VOLTAGE_LIMIT - input voltage limit programmed by charger. Indicates > > > +the voltage limit from a charging source. > > > +INPUT_POWER_LIMIT - input power limit programmed by charger. Indicates > > > +the power limit from a charging source. > > > > > > CHARGE_CONTROL_LIMIT - current charge control limit setting > > > CHARGE_CONTROL_LIMIT_MAX - maximum charge control limit setting > > > diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c > > > index 5358a80d854f..860db617d241 100644 > > > --- a/drivers/power/supply/power_supply_sysfs.c > > > +++ b/drivers/power/supply/power_supply_sysfs.c > > > @@ -275,6 +275,8 @@ static struct device_attribute power_supply_attrs[] = { > > > POWER_SUPPLY_ATTR(charge_control_limit), > > > POWER_SUPPLY_ATTR(charge_control_limit_max), > > > POWER_SUPPLY_ATTR(input_current_limit), > > > + POWER_SUPPLY_ATTR(input_voltage_limit), > > > + POWER_SUPPLY_ATTR(input_power_limit), > > > POWER_SUPPLY_ATTR(energy_full_design), > > > POWER_SUPPLY_ATTR(energy_empty_design), > > > POWER_SUPPLY_ATTR(energy_full), > > > diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h > > > index 2f9c201a54d1..ba135a5d8996 100644 > > > --- a/include/linux/power_supply.h > > > +++ b/include/linux/power_supply.h > > > @@ -122,6 +122,8 @@ enum power_supply_property { > > > POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT, > > > POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX, > > > POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT, > > > + POWER_SUPPLY_PROP_INPUT_VOLTAGE_LIMIT, > > > + POWER_SUPPLY_PROP_INPUT_POWER_LIMIT, > > > POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN, > > > POWER_SUPPLY_PROP_ENERGY_EMPTY_DESIGN, > > > POWER_SUPPLY_PROP_ENERGY_FULL, > > > -- > > > 2.20.1 > > > > > > > -- > > Benson Leung > > Staff Software Engineer > > Chrome OS Kernel > > Google Inc. > > bleung@google.com > > Chromium OS Project > > bleung@chromium.org [unhandled content-type:application/pgp-signature] | |