From f7a00ea959be31f9b742042294a359d508edce94 Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Fri, 20 Mar 2015 23:45:23 -0700 Subject: [PATCH] clk: Add safe switch hook Sometimes clocks can't accept their parent source turning off while the source is reprogrammed to a different rate. Most notably CPU clocks require a way to switch away from the current PLL they're running on, reprogram that PLL to a new rate, and then switch back to the PLL with the new rate once they're done. Add a hook that drivers can implement allowing them to return a 'safe parent' that they can switch their parent to while the upstream source is reprogrammed to support this. Signed-off-by: Stephen Boyd Signed-off-by: Ram Chandra Jangir --- drivers/clk/clk.c | 61 ++++++++++++++++++++++++++++++++++++++------ include/linux/clk-provider.h | 1 + 2 files changed, 54 insertions(+), 8 deletions(-) --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -51,9 +51,12 @@ struct clk_core { struct clk_core **parents; u8 num_parents; u8 new_parent_index; + u8 safe_parent_index; unsigned long rate; unsigned long req_rate; + unsigned long old_rate; unsigned long new_rate; + struct clk_core *safe_parent; struct clk_core *new_parent; struct clk_core *new_child; unsigned long flags; @@ -1271,7 +1274,8 @@ out: static void clk_calc_subtree(struct clk_core *core, unsigned long new_rate, struct clk_core *new_parent, u8 p_index) { - struct clk_core *child; + struct clk_core *child, *parent; + struct clk_hw *parent_hw; core->new_rate = new_rate; core->new_parent = new_parent; @@ -1281,6 +1285,18 @@ static void clk_calc_subtree(struct clk_ if (new_parent && new_parent != core->parent) new_parent->new_child = core; + if (core->ops->get_safe_parent) { + parent_hw = core->ops->get_safe_parent(core->hw); + if (parent_hw) { + parent = parent_hw->core; + p_index = clk_fetch_parent_index(core, parent); + core->safe_parent_index = p_index; + core->safe_parent = parent; + } + } else { + core->safe_parent = NULL; + } + hlist_for_each_entry(child, &core->children, child_node) { child->new_rate = clk_recalc(child, new_rate); clk_calc_subtree(child, child->new_rate, NULL, 0); @@ -1393,14 +1409,43 @@ static struct clk_core *clk_propagate_ra unsigned long event) { struct clk_core *child, *tmp_clk, *fail_clk = NULL; + struct clk_core *old_parent; int ret = NOTIFY_DONE; - if (core->rate == core->new_rate) + if (core->rate == core->new_rate && event != POST_RATE_CHANGE) return NULL; + switch (event) { + case PRE_RATE_CHANGE: + if (core->safe_parent) + core->ops->set_parent(core->hw, core->safe_parent_index); + core->old_rate = core->rate; + break; + case POST_RATE_CHANGE: + if (core->safe_parent) { + old_parent = __clk_set_parent_before(core, + core->new_parent); + if (core->ops->set_rate_and_parent) { + core->ops->set_rate_and_parent(core->hw, + core->new_rate, + core->new_parent ? + core->new_parent->rate : 0, + core->new_parent_index); + } else if (core->ops->set_parent) { + core->ops->set_parent(core->hw, + core->new_parent_index); + } + __clk_set_parent_after(core, core->new_parent, + old_parent); + } + break; + } + if (core->notifier_count) { - ret = __clk_notify(core, event, core->rate, core->new_rate); - if (ret & NOTIFY_STOP_MASK) + if (event != POST_RATE_CHANGE || core->old_rate != core->rate) + ret = __clk_notify(core, event, core->old_rate, + core->new_rate); + if (ret & NOTIFY_STOP_MASK && event != POST_RATE_CHANGE) fail_clk = core; } @@ -1446,7 +1491,8 @@ clk_change_rate(struct clk_core *core, u old_rate = core->rate; - if (core->new_parent && core->new_parent != core->parent) { + if (core->new_parent && core->new_parent != core->parent && + !core->safe_parent) { old_parent = __clk_set_parent_before(core, core->new_parent); trace_clk_set_parent(core, core->new_parent); @@ -1472,9 +1518,6 @@ clk_change_rate(struct clk_core *core, u core->rate = core->new_rate; - if (core->notifier_count && old_rate != core->rate) - __clk_notify(core, POST_RATE_CHANGE, old_rate, core->rate); - if (core->flags & CLK_RECALC_NEW_RATES) (void)clk_calc_new_rates(core, core->new_rate); @@ -1537,6 +1580,8 @@ static int clk_core_set_rate_nolock(stru core->req_rate = req_rate; + clk_propagate_rate_change(top, POST_RATE_CHANGE); + return ret; } --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -202,6 +202,7 @@ struct clk_ops { struct clk_rate_request *req); int (*set_parent)(struct clk_hw *hw, u8 index); u8 (*get_parent)(struct clk_hw *hw); + struct clk_hw *(*get_safe_parent)(struct clk_hw *hw); int (*set_rate)(struct clk_hw *hw, unsigned long rate, unsigned long parent_rate); int (*set_rate_and_parent)(struct clk_hw *hw,