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authorMaxime Ripard <maxime@cerno.tech>2022-02-25 15:35:25 +0100
committerStephen Boyd <sboyd@kernel.org>2022-03-11 19:14:39 -0800
commit10c46f2ea914202482d19cf80dcc9c321c9ff59b (patch)
tree7d657b99d5b5b488a051a9a687ed511f85d71b1f /drivers/clk/clk.c
parent723d0530d9d778cdceab4ebd0d0efc2d3a021c3c (diff)
clk: Enforce that disjoints limits are invalid
If we were to have two users of the same clock, doing something like: clk_set_rate_range(user1, 1000, 2000); clk_set_rate_range(user2, 3000, 4000); The second call would fail with -EINVAL, preventing from getting in a situation where we end up with impossible limits. However, this is never explicitly checked against and enforced, and works by relying on an undocumented behaviour of clk_set_rate(). Indeed, on the first clk_set_rate_range will make sure the current clock rate is within the new range, so it will be between 1000 and 2000Hz. On the second clk_set_rate_range(), it will consider (rightfully), that our current clock is outside of the 3000-4000Hz range, and will call clk_core_set_rate_nolock() to set it to 3000Hz. clk_core_set_rate_nolock() will then call clk_calc_new_rates() that will eventually check that our rate 3000Hz rate is outside the min 3000Hz max 2000Hz range, will bail out, the error will propagate and we'll eventually return -EINVAL. This solely relies on the fact that clk_calc_new_rates(), and in particular clk_core_determine_round_nolock(), won't modify the new rate allowing the error to be reported. That assumption won't be true for all drivers, and most importantly we'll break that assumption in a later patch. It can also be argued that we shouldn't even reach the point where we're calling clk_core_set_rate_nolock(). Let's make an explicit check for disjoints range before we're doing anything. Signed-off-by: Maxime Ripard <maxime@cerno.tech> Link: https://lore.kernel.org/r/20220225143534.405820-4-maxime@cerno.tech Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Diffstat (limited to 'drivers/clk/clk.c')
-rw-r--r--drivers/clk/clk.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index fff5edb89d6d..112911138a7b 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -632,6 +632,24 @@ static void clk_core_get_boundaries(struct clk_core *core,
*max_rate = min(*max_rate, clk_user->max_rate);
}
+static bool clk_core_check_boundaries(struct clk_core *core,
+ unsigned long min_rate,
+ unsigned long max_rate)
+{
+ struct clk *user;
+
+ lockdep_assert_held(&prepare_lock);
+
+ if (min_rate > core->max_rate || max_rate < core->min_rate)
+ return false;
+
+ hlist_for_each_entry(user, &core->clks, clks_node)
+ if (min_rate > user->max_rate || max_rate < user->min_rate)
+ return false;
+
+ return true;
+}
+
void clk_hw_set_rate_range(struct clk_hw *hw, unsigned long min_rate,
unsigned long max_rate)
{
@@ -2348,6 +2366,11 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
clk->min_rate = min;
clk->max_rate = max;
+ if (!clk_core_check_boundaries(clk->core, min, max)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
rate = clk_core_get_rate_nolock(clk->core);
if (rate < min || rate > max) {
/*
@@ -2376,6 +2399,7 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
}
}
+out:
if (clk->exclusive_count)
clk_core_rate_protect(clk->core);