From 4e88f3de89fbb7b5a5a0aca20376b276d26732ac Mon Sep 17 00:00:00 2001 From: Thierry Reding Date: Wed, 21 Jan 2015 17:13:00 +0100 Subject: [PATCH] clk: Introduce clk_has_parent() This new function is similar to clk_set_parent(), except that it doesn't actually change the parent. It merely checks that the given parent clock can be a parent for the given clock. A situation where this is useful is to check that a particular setup is valid before switching to it. One specific use-case for this is atomic modesetting in the DRM framework where setting a mode is divided into a check phase where a given configuration is validated before applying changes to the hardware. Cc: Russell King Signed-off-by: Thierry Reding Reviewed-by: Stephen Boyd Signed-off-by: Michael Turquette --- drivers/clk/clk.c | 30 ++++++++++++++++++++++++++++++ include/linux/clk.h | 17 +++++++++++++++++ 2 files changed, 47 insertions(+) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index f4963b7d4e17..5272ad71929f 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1651,6 +1651,36 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent) __clk_recalc_rates(clk, POST_RATE_CHANGE); } +/** + * clk_has_parent - check if a clock is a possible parent for another + * @clk: clock source + * @parent: parent clock source + * + * This function can be used in drivers that need to check that a clock can be + * the parent of another without actually changing the parent. + * + * Returns true if @parent is a possible parent for @clk, false otherwise. + */ +bool clk_has_parent(struct clk *clk, struct clk *parent) +{ + unsigned int i; + + /* NULL clocks should be nops, so return success if either is NULL. */ + if (!clk || !parent) + return true; + + /* Optimize for the case where the parent is already the parent. */ + if (clk->parent == parent) + return true; + + for (i = 0; i < clk->num_parents; i++) + if (strcmp(clk->parent_names[i], parent->name) == 0) + return true; + + return false; +} +EXPORT_SYMBOL_GPL(clk_has_parent); + /** * clk_set_parent - switch the parent of a mux clk * @clk: the mux clk whose input we are switching diff --git a/include/linux/clk.h b/include/linux/clk.h index c7f258a81761..ba7e9eda4347 100644 --- a/include/linux/clk.h +++ b/include/linux/clk.h @@ -301,6 +301,18 @@ long clk_round_rate(struct clk *clk, unsigned long rate); */ int clk_set_rate(struct clk *clk, unsigned long rate); +/** + * clk_has_parent - check if a clock is a possible parent for another + * @clk: clock source + * @parent: parent clock source + * + * This function can be used in drivers that need to check that a clock can be + * the parent of another without actually changing the parent. + * + * Returns true if @parent is a possible parent for @clk, false otherwise. + */ +bool clk_has_parent(struct clk *clk, struct clk *parent); + /** * clk_set_parent - set the parent clock source for this clock * @clk: clock source @@ -374,6 +386,11 @@ static inline long clk_round_rate(struct clk *clk, unsigned long rate) return 0; } +static inline bool clk_has_parent(struct clk *clk, struct clk *parent) +{ + return true; +} + static inline int clk_set_parent(struct clk *clk, struct clk *parent) { return 0; -- 2.20.1