From: Maxime Ripard <maxime@cerno.tech> To: Mike Turquette <mturquette@baylibre.com>, Stephen Boyd <sboyd@kernel.org> Cc: Dave Stevenson <dave.stevenson@raspberrypi.com>, Phil Elwell <phil@raspberrypi.com>, Tim Gover <tim.gover@raspberrypi.com>, Dom Cobley <dom@raspberrypi.com>, dri-devel@lists.freedesktop.org, linux-clk@vger.kernel.org, Maxime Ripard <maxime@cerno.tech> Subject: [PATCH v7 03/12] clk: Enforce that disjoints limits are invalid Date: Fri, 25 Feb 2022 15:35:25 +0100 [thread overview] Message-ID: <20220225143534.405820-4-maxime@cerno.tech> (raw) In-Reply-To: <20220225143534.405820-1-maxime@cerno.tech> 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> --- drivers/clk/clk.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) 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); -- 2.35.1
WARNING: multiple messages have this Message-ID (diff)
From: Maxime Ripard <maxime@cerno.tech> To: Mike Turquette <mturquette@baylibre.com>, Stephen Boyd <sboyd@kernel.org> Cc: Dom Cobley <dom@raspberrypi.com>, Tim Gover <tim.gover@raspberrypi.com>, Dave Stevenson <dave.stevenson@raspberrypi.com>, dri-devel@lists.freedesktop.org, Phil Elwell <phil@raspberrypi.com>, Maxime Ripard <maxime@cerno.tech>, linux-clk@vger.kernel.org Subject: [PATCH v7 03/12] clk: Enforce that disjoints limits are invalid Date: Fri, 25 Feb 2022 15:35:25 +0100 [thread overview] Message-ID: <20220225143534.405820-4-maxime@cerno.tech> (raw) In-Reply-To: <20220225143534.405820-1-maxime@cerno.tech> 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> --- drivers/clk/clk.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) 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); -- 2.35.1
next prev parent reply other threads:[~2022-02-25 14:35 UTC|newest] Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-02-25 14:35 [PATCH v7 00/12] clk: Improve clock range handling Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 01/12] clk: Fix clk_hw_get_clk() when dev is NULL Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 02/12] clk: Introduce Kunit Tests for the framework Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard [this message] 2022-02-25 14:35 ` [PATCH v7 03/12] clk: Enforce that disjoints limits are invalid Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 04/12] clk: Always clamp the rounded rate Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 05/12] clk: Use clamp instead of open-coding our own Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 06/12] clk: Always set the rate on clk_set_range_rate Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-03-22 19:05 ` Dmitry Osipenko 2022-03-22 19:05 ` Dmitry Osipenko 2022-03-23 8:51 ` Maxime Ripard 2022-03-23 8:51 ` Maxime Ripard 2022-03-24 19:09 ` Stephen Boyd 2022-03-24 19:09 ` Stephen Boyd 2022-03-24 19:25 ` Dmitry Osipenko 2022-03-24 19:25 ` Dmitry Osipenko 2022-02-25 14:35 ` [PATCH v7 07/12] clk: Add clk_drop_range Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 08/12] clk: bcm: rpi: Add variant structure Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 09/12] clk: bcm: rpi: Set a default minimum rate Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 10/12] clk: bcm: rpi: Run some clocks at the minimum rate allowed Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-02-25 14:35 ` [PATCH v7 11/12] drm/vc4: Add logging and comments Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-04-06 8:50 ` Thomas Zimmermann 2022-04-06 8:50 ` Thomas Zimmermann 2022-02-25 14:35 ` [PATCH v7 12/12] drm/vc4: hdmi: Remove clock rate initialization Maxime Ripard 2022-02-25 14:35 ` Maxime Ripard 2022-04-06 8:53 ` Thomas Zimmermann 2022-04-06 8:53 ` Thomas Zimmermann 2022-03-12 3:08 ` [PATCH v7 00/12] clk: Improve clock range handling Stephen Boyd 2022-03-12 3:08 ` Stephen Boyd 2022-03-16 8:37 ` Maxime Ripard 2022-03-16 8:37 ` Maxime Ripard 2022-04-06 10:42 ` Maxime Ripard 2022-04-06 10:42 ` Maxime Ripard
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