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Allow platform-code to disable the reset on probe and suspend/resume by setting a "disable-reset" boolean device property on the device. There are several reasons why the platform-code may want to disable the reset on probe and suspend/resume: 1) Resetting the charger should never be necessary it should always have sane values programmed. If it is running with invalid values while we are not running (system turned off or suspended) there is a big problem as that may lead to overcharging the battery. 2) The reset in suspend() is meant to put the charger back into default mode, but this is not necessary and not a good idea. If the charger has been programmed with a higher max charge_current / charge_voltage then putting it back in default-mode will reset those to the safe power-on defaults, leading to slower charging, or charging to a lower voltage (and thus not using the full capacity) while suspended which is undesirable. Reprogramming the max charge_current / charge_voltage after the reset will not help here as that will put the charger back in host mode and start the i2c watchdog if the host then does not do anything for 40s (iow if we're suspended for more then 40s) the watchdog expires resetting the device to default-mode, including resetting all the registers to there safe power-on defaults. So the only way to keep using custom charge settings while suspending is to keep the charger in its normal running state with the i2c watchdog disabled. This is fine as the charger will still automatically switch from constant current to constant voltage and stop charging when the battery is full. 3) Besides never being necessary resetting the charger also causes problems on systems where the charge voltage limit is set higher then the reset value, if this is the case and the charger is reset while charging and the battery voltage is between the 2 voltages, then about half the time the charger gets confused and claims to be charging (REG08 contains 0x64) but in reality the charger has decoupled itself from VBUS (Q1 off) and is drawing 0A from VBUS, leaving the system running from the battery. This last problem is happening on a GPD-win mini PC with a bq24292i charger chip combined with a max17047 fuel-gauge and a LiHV battery. I've checked and TI does not list any errata for the bq24292i which could explain this (there are no errata at all). Cc: Liam Breck <kernel@networkimprov.net> Cc: Tony Lindgren <tony@atomide.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Liam Breck <kernel@networkimprov.net> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk> |
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| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.