From 6562fbcf3ad5ffa56f1fc79bb1afae909cf3627b Mon Sep 17 00:00:00 2001 From: Jerome Brunet Date: Fri, 1 Dec 2017 22:52:00 +0100 Subject: [PATCH] clk: fix set_rate_range when current rate is out of range Calling clk_core_set_rate() with core->req_rate is basically a no-op because of the early bail-out mechanism. This may leave the clock in inconsistent state if the rate is out the requested range. Calling clk_core_set_rate() with the closest rate limit could solve the problem but: - The underlying determine_rate() callback needs to account for this corner case (rounding within the range, if possible) - if only round_rate() is available, we rely on luck unfortunately. Fixes: 1c8e600440c7 ("clk: Add rate constraints to clocks") Tested-by: Maxime Ripard Acked-by: Michael Turquette Signed-off-by: Jerome Brunet Signed-off-by: Michael Turquette Link: lkml.kernel.org/r/20171201215200.23523-11-jbrunet@baylibre.com --- drivers/clk/clk.c | 37 +++++++++++++++++++++++++++++++++---- 1 file changed, 33 insertions(+), 4 deletions(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 8e728f395b54..efbc802da3b3 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -2000,6 +2000,7 @@ EXPORT_SYMBOL_GPL(clk_set_rate_exclusive); int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max) { int ret = 0; + unsigned long old_min, old_max, rate; if (!clk) return 0; @@ -2016,10 +2017,38 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max) if (clk->exclusive_count) clk_core_rate_unprotect(clk->core); - if (min != clk->min_rate || max != clk->max_rate) { - clk->min_rate = min; - clk->max_rate = max; - ret = clk_core_set_rate_nolock(clk->core, clk->core->req_rate); + /* Save the current values in case we need to rollback the change */ + old_min = clk->min_rate; + old_max = clk->max_rate; + clk->min_rate = min; + clk->max_rate = max; + + rate = clk_core_get_rate_nolock(clk->core); + if (rate < min || rate > max) { + /* + * FIXME: + * We are in bit of trouble here, current rate is outside the + * the requested range. We are going try to request appropriate + * range boundary but there is a catch. It may fail for the + * usual reason (clock broken, clock protected, etc) but also + * because: + * - round_rate() was not favorable and fell on the wrong + * side of the boundary + * - the determine_rate() callback does not really check for + * this corner case when determining the rate + */ + + if (rate < min) + rate = min; + else + rate = max; + + ret = clk_core_set_rate_nolock(clk->core, rate); + if (ret) { + /* rollback the changes */ + clk->min_rate = old_min; + clk->max_rate = old_max; + } } if (clk->exclusive_count)