From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9542C10F12 for ; Mon, 15 Apr 2019 22:01:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1343218D3 for ; Mon, 15 Apr 2019 22:01:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727962AbfDOWBA (ORCPT ); Mon, 15 Apr 2019 18:01:00 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:47066 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725786AbfDOWBA (ORCPT ); Mon, 15 Apr 2019 18:01:00 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: eballetbo) with ESMTPSA id BEB6A281AC2 From: Enric Balletbo i Serra To: linux-pm@vger.kernel.org, sre@kernel.org Cc: Sameer Nanda , bleung@chromium.org, rjw@rjwysocki.net, gwendal@chromium.org, linux-kernel@vger.kernel.org, Len Brown , groeck@chromium.org, Adam.Thomson.Opensource@diasemi.com, kernel@collabora.com, Pavel Machek Subject: [RESEND PATCH v3 1/2] power: supply: add input voltage limit property Date: Tue, 16 Apr 2019 00:00:48 +0200 Message-Id: <20190415220049.14924-1-enric.balletbo@collabora.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is part of 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, ie 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 Reviewed-by: Guenter Roeck Acked-by: Adam Thomson --- 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 | 15 +++++++++++++++ Documentation/power/power_supply_class.txt | 2 ++ drivers/power/supply/power_supply_sysfs.c | 1 + include/linux/power_supply.h | 1 + 4 files changed, 19 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-class-power b/Documentation/ABI/testing/sysfs-class-power index 5e23e22dce1b..6dee5c105a28 100644 --- a/Documentation/ABI/testing/sysfs-class-power +++ b/Documentation/ABI/testing/sysfs-class-power @@ -335,6 +335,21 @@ Description: Access: Read, Write Valid values: Represented in microamps +What: /sys/class/power_supply//input_voltage_limit +Date: Nov 2018 +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. + + Access: Read, Write + Valid values: Represented in microvolts + What: /sys/class/power_supply//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..7b4be615b4f8 100644 --- a/Documentation/power/power_supply_class.txt +++ b/Documentation/power/power_supply_class.txt @@ -137,6 +137,8 @@ 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. 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 dce24f596160..5848742ebb59 100644 --- a/drivers/power/supply/power_supply_sysfs.c +++ b/drivers/power/supply/power_supply_sysfs.c @@ -275,6 +275,7 @@ 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(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..5cb0d0b5eb19 100644 --- a/include/linux/power_supply.h +++ b/include/linux/power_supply.h @@ -122,6 +122,7 @@ 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_ENERGY_FULL_DESIGN, POWER_SUPPLY_PROP_ENERGY_EMPTY_DESIGN, POWER_SUPPLY_PROP_ENERGY_FULL, -- 2.20.1