696861761a
On Odroid XU3/4 and other Exynos5422 based boards there is a case, that different devices on the board are supplied by different regulators with non-fixed voltages. If one of these devices temporarily requires higher voltage, there might occur a situation that the spread between two devices' voltages is so high, that there is a risk of changing 'high' and 'low' states on the interconnection between devices powered by those regulators. Introduce new function regulator_balance_voltage(), which keeps max_spread constraint fulfilled between a group of coupled regulators. It should be called if a regulator changes its voltage or after disabling or enabling. Disabled regulators should follow changes of the enabled ones, but their consumers' demands shouldn't be taken into account while calculating voltage of other coupled regulators. Find voltages, which are closest to suiting all the consumers' demands, while fulfilling max_spread constraint, keeping the following rules: - if one regulator is about to rise its voltage, rise others voltages in order to keep the max_spread - if a regulator, which has caused rising other regulators, is lowered, lower other regulators if possible - if one regulator is about to lower its voltage, but it hasn't caused rising other regulators, don't change its voltage if it breaks the max_spread Change regulators' voltages step by step, keeping max_spread constraint fulfilled all the time. Function regulator_get_optimal_voltage() should find the best possible change for the regulator, which doesn't break max_spread constraint. In function regulator_balance_voltage() optimize number of steps by finding highest voltage difference on each iteration. If a regulator, which is about to change its voltage, is not coupled, method regulator_get_optimal_voltage() should simply return the lowest voltage fulfilling consumers' demands. Coupling should be checked only if the system is in PM_SUSPEND_ON state. Signed-off-by: Maciej Purski <m.purski@samsung.com> Signed-off-by: Mark Brown <broonie@kernel.org> |
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.