From 71472c0c06cf9a3d1540762ea205654c584e3bc4 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Mon, 29 Jul 2013 12:25:00 +0100 Subject: clk: add support for clock reparent on set_rate Add core support to allow clock implementations to select the best parent clock when rounding a rate, e.g. the one which can provide the closest clock rate to that requested. This is by way of adding a new clock op, determine_rate(), which is like round_rate() but has an extra parameter to allow the clock implementation to optionally select a different parent clock. The core then takes care of reparenting the clock when setting the rate. The parent change takes place with the help of some new private data members. struct clk::new_parent specifies a clock's new parent (NULL indicates no change), and struct clk::new_child specifies a clock's new child (whose new_parent member points back to it). The purpose of these are to allow correct walking of the future tree for notifications prior to actually reparenting any clocks, specifically to skip child clocks who are being reparented to another clock (they will be notified via the new parent), and to include any new child clock. These pointers are set by clk_calc_subtree(), and the new_child pointer gets cleared when a child is actually reparented to avoid duplicate POST_RATE_CHANGE notifications. Each place where round_rate() is called, determine_rate() is checked first and called in preference. This restructures a few of the call sites to simplify the logic into if/else blocks. Signed-off-by: James Hogan Reviewed-by: Stephen Boyd Cc: Mike Turquette Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Mike Turquette --- include/linux/clk-provider.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux/clk-provider.h') diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index a83409285a7f..4f525b37c6fd 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -79,6 +79,10 @@ struct clk_hw; * @round_rate: Given a target rate as input, returns the closest rate actually * supported by the clock. * + * @determine_rate: Given a target rate as input, returns the closest rate + * actually supported by the clock, and optionally the parent clock + * that should be used to provide the clock rate. + * * @get_parent: Queries the hardware to determine the parent of a clock. The * return value is a u8 which specifies the index corresponding to * the parent clock. This index can be applied to either the @@ -126,6 +130,9 @@ struct clk_ops { unsigned long parent_rate); long (*round_rate)(struct clk_hw *hw, unsigned long, unsigned long *); + long (*determine_rate)(struct clk_hw *hw, unsigned long rate, + unsigned long *best_parent_rate, + struct clk **best_parent_clk); int (*set_parent)(struct clk_hw *hw, u8 index); u8 (*get_parent)(struct clk_hw *hw); int (*set_rate)(struct clk_hw *hw, unsigned long, -- cgit v1.2.3