clk: add clk_rate_exclusive api
Using clock rate protection, we can now provide a way for clock consumer to claim exclusive control over the rate of a producer So far, rate change operations have been a "last write wins" affair. This changes allows drivers to explicitly protect against this behavior, if required. Of course, if exclusivity over a producer is claimed more than once, the rate is effectively locked as exclusivity cannot be preempted 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/20171201215200.23523-10-jbrunet@baylibre.com
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@ -87,6 +87,7 @@ struct clk {
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const char *con_id;
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unsigned long min_rate;
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unsigned long max_rate;
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unsigned int exclusive_count;
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struct hlist_node clks_node;
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};
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@ -565,6 +566,45 @@ static int clk_core_rate_nuke_protect(struct clk_core *core)
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return ret;
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}
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/**
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* clk_rate_exclusive_put - release exclusivity over clock rate control
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* @clk: the clk over which the exclusivity is released
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*
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* clk_rate_exclusive_put() completes a critical section during which a clock
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* consumer cannot tolerate any other consumer making any operation on the
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* clock which could result in a rate change or rate glitch. Exclusive clocks
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* cannot have their rate changed, either directly or indirectly due to changes
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* further up the parent chain of clocks. As a result, clocks up parent chain
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* also get under exclusive control of the calling consumer.
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*
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* If exlusivity is claimed more than once on clock, even by the same consumer,
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* the rate effectively gets locked as exclusivity can't be preempted.
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*
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* Calls to clk_rate_exclusive_put() must be balanced with calls to
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* clk_rate_exclusive_get(). Calls to this function may sleep, and do not return
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* error status.
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*/
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void clk_rate_exclusive_put(struct clk *clk)
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{
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if (!clk)
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return;
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clk_prepare_lock();
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/*
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* if there is something wrong with this consumer protect count, stop
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* here before messing with the provider
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*/
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if (WARN_ON(clk->exclusive_count <= 0))
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goto out;
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clk_core_rate_unprotect(clk->core);
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clk->exclusive_count--;
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out:
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clk_prepare_unlock();
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}
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EXPORT_SYMBOL_GPL(clk_rate_exclusive_put);
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static void clk_core_rate_protect(struct clk_core *core)
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{
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lockdep_assert_held(&prepare_lock);
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@ -592,6 +632,38 @@ static void clk_core_rate_restore_protect(struct clk_core *core, int count)
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core->protect_count = count;
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}
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/**
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* clk_rate_exclusive_get - get exclusivity over the clk rate control
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* @clk: the clk over which the exclusity of rate control is requested
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*
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* clk_rate_exlusive_get() begins a critical section during which a clock
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* consumer cannot tolerate any other consumer making any operation on the
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* clock which could result in a rate change or rate glitch. Exclusive clocks
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* cannot have their rate changed, either directly or indirectly due to changes
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* further up the parent chain of clocks. As a result, clocks up parent chain
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* also get under exclusive control of the calling consumer.
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*
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* If exlusivity is claimed more than once on clock, even by the same consumer,
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* the rate effectively gets locked as exclusivity can't be preempted.
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*
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* Calls to clk_rate_exclusive_get() should be balanced with calls to
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* clk_rate_exclusive_put(). Calls to this function may sleep.
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* Returns 0 on success, -EERROR otherwise
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*/
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int clk_rate_exclusive_get(struct clk *clk)
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{
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if (!clk)
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return 0;
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clk_prepare_lock();
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clk_core_rate_protect(clk->core);
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clk->exclusive_count++;
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clk_prepare_unlock();
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return 0;
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}
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EXPORT_SYMBOL_GPL(clk_rate_exclusive_get);
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static void clk_core_unprepare(struct clk_core *core)
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{
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lockdep_assert_held(&prepare_lock);
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@ -988,6 +1060,12 @@ static int clk_core_determine_round_nolock(struct clk_core *core,
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if (!core)
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return 0;
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/*
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* At this point, core protection will be disabled if
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* - if the provider is not protected at all
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* - if the calling consumer is the only one which has exclusivity
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* over the provider
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*/
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if (clk_core_rate_is_protected(core)) {
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req->rate = core->rate;
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} else if (core->ops->determine_rate) {
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@ -1104,10 +1182,17 @@ long clk_round_rate(struct clk *clk, unsigned long rate)
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clk_prepare_lock();
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if (clk->exclusive_count)
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clk_core_rate_unprotect(clk->core);
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clk_core_get_boundaries(clk->core, &req.min_rate, &req.max_rate);
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req.rate = rate;
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ret = clk_core_round_rate_nolock(clk->core, &req);
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if (clk->exclusive_count)
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clk_core_rate_protect(clk->core);
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clk_prepare_unlock();
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if (ret)
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@ -1843,14 +1928,67 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
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/* prevent racing with updates to the clock topology */
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clk_prepare_lock();
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if (clk->exclusive_count)
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clk_core_rate_unprotect(clk->core);
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ret = clk_core_set_rate_nolock(clk->core, rate);
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if (clk->exclusive_count)
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clk_core_rate_protect(clk->core);
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clk_prepare_unlock();
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return ret;
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}
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EXPORT_SYMBOL_GPL(clk_set_rate);
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/**
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* clk_set_rate_exclusive - specify a new rate get exclusive control
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* @clk: the clk whose rate is being changed
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* @rate: the new rate for clk
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*
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* This is a combination of clk_set_rate() and clk_rate_exclusive_get()
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* within a critical section
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*
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* This can be used initially to ensure that at least 1 consumer is
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* statisfied when several consumers are competing for exclusivity over the
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* same clock provider.
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*
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* The exclusivity is not applied if setting the rate failed.
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*
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* Calls to clk_rate_exclusive_get() should be balanced with calls to
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* clk_rate_exclusive_put().
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*
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* Returns 0 on success, -EERROR otherwise.
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*/
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int clk_set_rate_exclusive(struct clk *clk, unsigned long rate)
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{
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int ret;
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if (!clk)
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return 0;
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/* prevent racing with updates to the clock topology */
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clk_prepare_lock();
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/*
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* The temporary protection removal is not here, on purpose
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* This function is meant to be used instead of clk_rate_protect,
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* so before the consumer code path protect the clock provider
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*/
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ret = clk_core_set_rate_nolock(clk->core, rate);
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if (!ret) {
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clk_core_rate_protect(clk->core);
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clk->exclusive_count++;
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}
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clk_prepare_unlock();
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return ret;
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}
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EXPORT_SYMBOL_GPL(clk_set_rate_exclusive);
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/**
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* clk_set_rate_range - set a rate range for a clock source
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* @clk: clock source
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@ -1875,12 +2013,18 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
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clk_prepare_lock();
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if (clk->exclusive_count)
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clk_core_rate_unprotect(clk->core);
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if (min != clk->min_rate || max != clk->max_rate) {
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clk->min_rate = min;
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clk->max_rate = max;
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ret = clk_core_set_rate_nolock(clk->core, clk->core->req_rate);
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}
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if (clk->exclusive_count)
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clk_core_rate_protect(clk->core);
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clk_prepare_unlock();
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return ret;
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@ -2091,8 +2235,16 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
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return 0;
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clk_prepare_lock();
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if (clk->exclusive_count)
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clk_core_rate_unprotect(clk->core);
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ret = clk_core_set_parent_nolock(clk->core,
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parent ? parent->core : NULL);
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if (clk->exclusive_count)
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clk_core_rate_protect(clk->core);
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clk_prepare_unlock();
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return ret;
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@ -2154,7 +2306,15 @@ int clk_set_phase(struct clk *clk, int degrees)
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degrees += 360;
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clk_prepare_lock();
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if (clk->exclusive_count)
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clk_core_rate_unprotect(clk->core);
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ret = clk_core_set_phase_nolock(clk->core, degrees);
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if (clk->exclusive_count)
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clk_core_rate_protect(clk->core);
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clk_prepare_unlock();
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return ret;
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@ -3175,6 +3335,18 @@ void __clk_put(struct clk *clk)
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clk_prepare_lock();
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/*
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* Before calling clk_put, all calls to clk_rate_exclusive_get() from a
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* given user should be balanced with calls to clk_rate_exclusive_put()
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* and by that same consumer
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*/
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if (WARN_ON(clk->exclusive_count)) {
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/* We voiced our concern, let's sanitize the situation */
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clk->core->protect_count -= (clk->exclusive_count - 1);
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clk_core_rate_unprotect(clk->core);
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clk->exclusive_count = 0;
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}
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hlist_del(&clk->clks_node);
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if (clk->min_rate > clk->core->req_rate ||
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clk->max_rate < clk->core->req_rate)
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@ -331,6 +331,38 @@ struct clk *devm_clk_get(struct device *dev, const char *id);
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*/
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struct clk *devm_get_clk_from_child(struct device *dev,
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struct device_node *np, const char *con_id);
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/**
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* clk_rate_exclusive_get - get exclusivity over the rate control of a
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* producer
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* @clk: clock source
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*
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* This function allows drivers to get exclusive control over the rate of a
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* provider. It prevents any other consumer to execute, even indirectly,
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* opereation which could alter the rate of the provider or cause glitches
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*
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* If exlusivity is claimed more than once on clock, even by the same driver,
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* the rate effectively gets locked as exclusivity can't be preempted.
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*
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* Must not be called from within atomic context.
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*
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* Returns success (0) or negative errno.
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*/
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int clk_rate_exclusive_get(struct clk *clk);
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/**
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* clk_rate_exclusive_put - release exclusivity over the rate control of a
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* producer
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* @clk: clock source
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*
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* This function allows drivers to release the exclusivity it previously got
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* from clk_rate_exclusive_get()
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*
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* The caller must balance the number of clk_rate_exclusive_get() and
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* clk_rate_exclusive_put() calls.
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*
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* Must not be called from within atomic context.
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*/
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void clk_rate_exclusive_put(struct clk *clk);
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/**
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* clk_enable - inform the system when the clock source should be running.
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*/
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int clk_set_rate(struct clk *clk, unsigned long rate);
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/**
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* clk_set_rate_exclusive- set the clock rate and claim exclusivity over
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* clock source
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* @clk: clock source
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* @rate: desired clock rate in Hz
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*
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* This helper function allows drivers to atomically set the rate of a producer
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* and claim exclusivity over the rate control of the producer.
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*
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* It is essentially a combination of clk_set_rate() and
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* clk_rate_exclusite_get(). Caller must balance this call with a call to
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* clk_rate_exclusive_put()
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*
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* Returns success (0) or negative errno.
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*/
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int clk_set_rate_exclusive(struct clk *clk, unsigned long rate);
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/**
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* clk_has_parent - check if a clock is a possible parent for another
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* @clk: clock source
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@ -583,6 +632,14 @@ static inline void clk_bulk_put(int num_clks, struct clk_bulk_data *clks) {}
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static inline void devm_clk_put(struct device *dev, struct clk *clk) {}
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static inline int clk_rate_exclusive_get(struct clk *clk)
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{
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return 0;
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}
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static inline void clk_rate_exclusive_put(struct clk *clk) {}
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static inline int clk_enable(struct clk *clk)
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{
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return 0;
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@ -609,6 +666,11 @@ static inline int clk_set_rate(struct clk *clk, unsigned long rate)
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return 0;
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}
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static inline int clk_set_rate_exclusive(struct clk *clk, unsigned long rate)
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{
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return 0;
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}
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static inline long clk_round_rate(struct clk *clk, unsigned long rate)
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{
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return 0;
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