From 0bfa0820c274b019583b3454c6c889c99c24558d Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Mon, 25 Jan 2021 14:29:18 -0500 Subject: PM: clk: make PM clock layer compatible with clocks that must sleep The clock API splits its interface into sleepable ant atomic contexts: - clk_prepare/clk_unprepare for stuff that might sleep - clk_enable_clk_disable for anything that may be done in atomic context The code handling runtime PM for clocks only calls clk_disable() on suspend requests, and clk_enable on resume requests. This means that runtime PM with clock providers that only have the prepare/unprepare methods implemented is basically useless. Many clock implementations can't accommodate atomic contexts. This is often the case when communication with the clock happens through another subsystem like I2C or SCMI. Let's make the clock PM code useful with such clocks by safely invoking clk_prepare/clk_unprepare upon resume/suspend requests. Of course, when such clocks are registered with the PM layer then pm_runtime_irq_safe() can't be used, and neither pm_runtime_suspend() nor pm_runtime_resume() may be invoked in atomic context. For clocks that do implement the enable and disable methods then everything just works as before. A note on sparse: According to https://lwn.net/Articles/109066/ there are things that sparse can't cope with. In particular, pm_clk_op_lock() and pm_clk_op_unlock() may or may not lock/unlock psd->lock depending on some runtime condition. To work around that we tell it the lock is always untaken for the purpose of static analisys. Thanks to Naresh Kamboju for reporting issues with the initial patch. Signed-off-by: Nicolas Pitre Tested-by: Naresh Kamboju Signed-off-by: Rafael J. Wysocki --- drivers/clk/clk.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'drivers/clk/clk.c') diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 8c1d04db990d..3d751ae5bc70 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1164,6 +1164,27 @@ int clk_enable(struct clk *clk) } EXPORT_SYMBOL_GPL(clk_enable); +/** + * clk_is_enabled_when_prepared - indicate if preparing a clock also enables it. + * @clk: clock source + * + * Returns true if clk_prepare() implicitly enables the clock, effectively + * making clk_enable()/clk_disable() no-ops, false otherwise. + * + * This is of interest mainly to power management code where actually + * disabling the clock also requires unpreparing it to have any material + * effect. + * + * Regardless of the value returned here, the caller must always invoke + * clk_enable() or clk_prepare_enable() and counterparts for usage counts + * to be right. + */ +bool clk_is_enabled_when_prepared(struct clk *clk) +{ + return clk && !(clk->core->ops->enable && clk->core->ops->disable); +} +EXPORT_SYMBOL_GPL(clk_is_enabled_when_prepared); + static int clk_core_prepare_enable(struct clk_core *core) { int ret; -- cgit v1.2.3