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authorJerome Brunet <jbrunet@baylibre.com>2017-12-01 22:52:00 +0100
committerMichael Turquette <mturquette@baylibre.com>2017-12-19 16:35:35 -0800
commit6562fbcf3ad5ffa56f1fc79bb1afae909cf3627b (patch)
treed378f55d810afab8770c25d7c78b7361ce14ddf4 /drivers/clk
parent55e9b8b7b806ec3f9a8817e13596682a5981c19c (diff)
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 <maxime.ripard@free-electrons.com> Acked-by: Michael Turquette <mturquette@baylibre.com> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> Signed-off-by: Michael Turquette <mturquette@baylibre.com> Link: lkml.kernel.org/r/20171201215200.23523-11-jbrunet@baylibre.com
Diffstat (limited to 'drivers/clk')
-rw-r--r--drivers/clk/clk.c37
1 files 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)

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