Introduce a new helper that recursively walks through all children and their descendants, calculating the lowest common multiple (LCM) of their rates. For the requesting child, it uses the requested rate; for other enabled children, it uses their current rate. This is useful for determining what parent rate can satisfy all children through simple integer dividers.
Link: https://lore.kernel.org/linux-clk/[email protected]/ Link: https://lpc.events/event/19/contributions/2152/ Signed-off-by: Brian Masney <[email protected]> --- drivers/clk/clk.c | 49 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/clk-provider.h | 2 ++ 2 files changed, 51 insertions(+) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 47093cda9df32223c1120c3710261296027c4cd3..f1afd6c93eba49b9fc6c5c0e1db11d46c79069e9 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -14,6 +14,7 @@ #include <linux/err.h> #include <linux/hashtable.h> #include <linux/init.h> +#include <linux/lcm.h> #include <linux/list.h> #include <linux/module.h> #include <linux/mutex.h> @@ -838,6 +839,54 @@ void clk_hw_set_rate_range(struct clk_hw *hw, unsigned long min_rate, } EXPORT_SYMBOL_GPL(clk_hw_set_rate_range); +/** + * clk_hw_get_children_lcm - Calculate LCM of all children's rates recursively + * @hw: The parent clock hardware + * @requesting_hw: The child clock that is requesting a rate change (can be NULL) + * @requesting_rate: The target rate for the requesting clock + * + * This helper recursively walks through all children and their descendants, + * calculating the lowest common multiple (LCM) of their rates. For the + * requesting child, it uses the requested rate; for other enabled children, it + * uses their current rate. This is useful for determining what parent rate can + * satisfy all children through simple integer dividers. + * + * Returns: The LCM of all non-zero rates found in the subtree, or 0 if no valid rates. + */ +unsigned long clk_hw_get_children_lcm(struct clk_hw *hw, struct clk_hw *requesting_hw, + unsigned long requesting_rate) +{ + unsigned long lcm_rate = 0; + unsigned long child_rate; + struct clk_core *child; + + hlist_for_each_entry(child, &hw->core->children, child_node) { + /* Use requesting rate for the requesting child, current rate for others */ + if (child->hw == requesting_hw) { + child_rate = requesting_rate; + } else { + if (!clk_hw_is_enabled(child->hw)) + continue; + + child_rate = clk_hw_get_rate(child->hw); + } + + if (lcm_rate == 0) + lcm_rate = child_rate; + else + lcm_rate = lcm(lcm_rate, child_rate); + + /* Recursively get LCM of this child's children */ + child_rate = clk_hw_get_children_lcm(child->hw, requesting_hw, + requesting_rate); + if (child_rate > 0) + lcm_rate = lcm(lcm_rate, child_rate); + } + + return lcm_rate; +} +EXPORT_SYMBOL_GPL(clk_hw_get_children_lcm); + /* * __clk_mux_determine_rate - clk_ops::determine_rate implementation for a mux type clk * @hw: mux type clk to determine rate on diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index 630705a47129453c241f1b1755f2c2f2a7ed8f77..2699b9759e13d0c1f0b54f4fa4f7f7bdd42e8dde 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -1430,6 +1430,8 @@ void clk_hw_get_rate_range(struct clk_hw *hw, unsigned long *min_rate, unsigned long *max_rate); void clk_hw_set_rate_range(struct clk_hw *hw, unsigned long min_rate, unsigned long max_rate); +unsigned long clk_hw_get_children_lcm(struct clk_hw *hw, struct clk_hw *requesting_hw, + unsigned long requesting_rate); static inline void __clk_hw_set_clk(struct clk_hw *dst, struct clk_hw *src) { -- 2.53.0
