[PATCH v2 05/11] clk: add support for clock protection
Michael Turquette
mturquette at baylibre.com
Thu May 25 13:58:52 PDT 2017
Quoting Jerome Brunet (2017-05-21 14:59:52)
> The patch adds clk_protect and clk_unprotect to the CCF API. These
> functions allow a consumer to inform the system that the rate of clock is
> critical to for its operations and it can't tolerate other consumers
> changing the rate or introducing glitches while the clock is protected.
>
> Signed-off-by: Jerome Brunet <jbrunet at baylibre.com>
> ---
> drivers/clk/clk.c | 207 +++++++++++++++++++++++++++++++++++++++++--
> include/linux/clk-provider.h | 1 +
> include/linux/clk.h | 29 ++++++
> 3 files changed, 230 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 1a8c0d013238..a0524e3bfaca 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -60,6 +60,7 @@ struct clk_core {
> bool orphan;
> unsigned int enable_count;
> unsigned int prepare_count;
> + unsigned int protect_count;
> unsigned long min_rate;
> unsigned long max_rate;
> unsigned long accuracy;
> @@ -84,6 +85,7 @@ struct clk {
> const char *con_id;
> unsigned long min_rate;
> unsigned long max_rate;
> + unsigned long protect_count;
> struct hlist_node clks_node;
> };
>
> @@ -160,6 +162,11 @@ static bool clk_core_is_prepared(struct clk_core *core)
> return core->ops->is_prepared(core->hw);
> }
>
> +static bool clk_core_rate_is_protected(struct clk_core *core)
> +{
> + return core->protect_count;
> +}
> +
> static bool clk_core_is_enabled(struct clk_core *core)
> {
> /*
> @@ -328,6 +335,11 @@ bool clk_hw_is_prepared(const struct clk_hw *hw)
> return clk_core_is_prepared(hw->core);
> }
>
> +bool clk_hw_rate_is_protected(const struct clk_hw *hw)
> +{
> + return clk_core_rate_is_protected(hw->core);
> +}
> +
> bool clk_hw_is_enabled(const struct clk_hw *hw)
> {
> return clk_core_is_enabled(hw->core);
> @@ -584,6 +596,102 @@ int clk_prepare(struct clk *clk)
> }
> EXPORT_SYMBOL_GPL(clk_prepare);
>
> +static void clk_core_rate_unprotect(struct clk_core *core)
> +{
> + lockdep_assert_held(&prepare_lock);
> +
> + if (!core)
> + return;
> +
> + if (WARN_ON(core->protect_count == 0))
> + return;
> +
> + if (--core->protect_count > 0)
> + return;
> +
> + clk_core_rate_unprotect(core->parent);
> +}
> +
> +/**
> + * clk_rate_unprotect - unprotect the rate of a clock source
> + * @clk: the clk being unprotected
> + *
> + * clk_unprotect completes a critical section during which the clock
> + * consumer cannot tolerate any change to the clock rate. If no other clock
> + * consumers have protected clocks in the parent chain, then calls to this
> + * function will allow the clocks in the parent chain to change rates
> + * freely.
> + *
> + * Unlike the clk_set_rate_range method, which allows the rate to change
> + * within a given range, protected clocks cannot have their rate changed,
> + * either directly or indirectly due to changes further up the parent chain
> + * of clocks.
> + *
> + * Calls to clk_unprotect must be balanced with calls to clk_protect. Calls
> + * to this function may sleep, and do not return error status.
> + */
> +void clk_rate_unprotect(struct clk *clk)
> +{
> + if (!clk)
> + return;
> +
> + clk_prepare_lock();
> +
> + /*
> + * if there is something wrong with this consumer protect count, stop
> + * here before messing with the provider
> + */
> + if (WARN_ON(clk->protect_count <= 0))
> + goto out;
> +
> + clk_core_rate_unprotect(clk->core);
> + clk->protect_count--;
> +out:
> + clk_prepare_unlock();
> +}
> +EXPORT_SYMBOL_GPL(clk_rate_unprotect);
> +
> +static void clk_core_rate_protect(struct clk_core *core)
> +{
> + lockdep_assert_held(&prepare_lock);
> +
> + if (!core)
> + return;
> +
> + if (core->protect_count == 0)
> + clk_core_rate_protect(core->parent);
> +
> + core->protect_count++;
> +}
> +
> +/**
> + * clk_rate_protect - protect a clock source
> + * @clk: the clk being protected
> + *
> + * clk_protect begins a critical section during which the clock consumer
> + * cannot tolerate any change to the clock rate. This results in all clocks
> + * up the parent chain to also be rate-protected.
> + *
> + * Unlike the clk_set_rate_range method, which allows the rate to change
> + * within a given range, protected clocks cannot have their rate changed,
> + * either directly or indirectly due to changes further up the parent chain
> + * of clocks.
> + *
> + * Calls to clk_protect should be balanced with calls to clk_unprotect.
> + * Calls to this function may sleep, and do not return error status.
> + */
> +void clk_rate_protect(struct clk *clk)
> +{
> + if (!clk)
> + return;
> +
> + clk_prepare_lock();
> + clk_core_rate_protect(clk->core);
> + clk->protect_count++;
> + clk_prepare_unlock();
> +}
> +EXPORT_SYMBOL_GPL(clk_rate_protect);
> +
> static void clk_core_disable(struct clk_core *core)
> {
> lockdep_assert_held(&enable_lock);
> @@ -838,7 +946,15 @@ static int clk_core_determine_round(struct clk_core *core,
> {
> long rate;
>
> - if (core->ops->determine_rate) {
> + /*
> + * At this point, core protection will be disabled if
> + * - if the provider is not protected at all
> + * - if the calling consumer is the only one protecting the
> + * provider (and only once)
> + */
> + if (clk_core_rate_is_protected(core)) {
> + req->rate = core->rate;
> + } else if (core->ops->determine_rate) {
> return core->ops->determine_rate(core->hw, req);
> } else if (core->ops->round_rate) {
> rate = core->ops->round_rate(core->hw, req->rate,
> @@ -944,10 +1060,17 @@ long clk_round_rate(struct clk *clk, unsigned long rate)
>
> clk_prepare_lock();
>
> + if (clk->protect_count)
> + clk_core_rate_unprotect(clk->core);
> +
> clk_core_get_boundaries(clk->core, &req.min_rate, &req.max_rate);
> req.rate = rate;
>
> ret = clk_core_round_rate_nolock(clk->core, &req);
> +
> + if (clk->protect_count)
> + clk_core_rate_protect(clk->core);
> +
> clk_prepare_unlock();
>
> if (ret)
> @@ -1575,15 +1698,24 @@ static unsigned long clk_core_req_round_rate_nolock(struct clk_core *core,
There are way too many round_rate and determine_rate functions.
Here is a list of round_rate and determine_rate "helpers":
static int clk_core_determine_round(struct clk_core *core,
struct clk_rate_request *req)
(called by clk_core_round_rate_nolock and clk_calc_new_rates)
static int clk_core_round_rate_nolock(struct clk_core *core,
struct clk_rate_request *req)
(called in several places)
int __clk_determine_rate(struct clk_hw *hw, struct clk_rate_request *req)
(called by a few provider drivers. Should probably be renamed as I
mentioned in my previous response)
unsigned long clk_hw_round_rate(struct clk_hw *hw, unsigned long rate)
(used a whole lot)
static unsigned long clk_core_req_round_rate_nolock(struct clk_core *core,
unsigned long req_rate)
(only called by clk_core_set_rate_nolock. Can we replace with one of the
options above? Probably clk_core_round_rate_nolock)
> {
> int ret;
> struct clk_rate_request req;
> + unsigned int cnt = core->protect_count;
>
> if (!core)
> return 0;
>
> + /* simulate what the rate would be if it could be freely set */
> + while (core->protect_count)
> + clk_core_rate_unprotect(core);
Gross. Why do this here and not in similar functions like
clk_core_round_rate_nolock?
> +
> clk_core_get_boundaries(core, &req.min_rate, &req.max_rate);
> req.rate = req_rate;
>
> ret = clk_core_round_rate_nolock(core, &req);
>
> + /* restore the protection */
> + while (core->protect_count < cnt)
> + clk_core_rate_protect(core);
> +
> return ret ? 0 : req.rate;
> }
>
> @@ -1602,6 +1734,10 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
> if (rate == clk_core_get_rate_nolock(core))
> return 0;
>
> + /* fail on a direct rate set of a protected provider */
> + if (clk_core_rate_is_protected(core))
> + return -EBUSY;
Again, why bother unrolling the protected clocks in
clk_core_req_round_rate_nolock if any protection will cause the
operation to fail here?
Best regards,
Mike
> +
> if ((core->flags & CLK_SET_RATE_GATE) && core->prepare_count)
> return -EBUSY;
>
> @@ -1658,8 +1794,14 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
> /* prevent racing with updates to the clock topology */
> clk_prepare_lock();
>
> + if (clk->protect_count)
> + clk_core_rate_unprotect(clk->core);
> +
> ret = clk_core_set_rate_nolock(clk->core, rate);
>
> + if (clk->protect_count)
> + clk_core_rate_protect(clk->core);
> +
> clk_prepare_unlock();
>
> return ret;
> @@ -1690,12 +1832,18 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
>
> clk_prepare_lock();
>
> + if (clk->protect_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);
> }
>
> + if (clk->protect_count)
> + clk_core_rate_protect(clk->core);
> +
> clk_prepare_unlock();
>
> return ret;
> @@ -1837,6 +1985,9 @@ static int clk_core_set_parent_nolock(struct clk_core *core,
> if ((core->flags & CLK_SET_PARENT_GATE) && core->prepare_count)
> return -EBUSY;
>
> + if (clk_core_rate_is_protected(core))
> + return -EBUSY;
> +
> /* try finding the new parent index */
> if (parent) {
> p_index = clk_fetch_parent_index(core, parent);
> @@ -1894,8 +2045,16 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
> return 0;
>
> clk_prepare_lock();
> +
> + if (clk->protect_count)
> + clk_core_rate_unprotect(clk->core);
> +
> ret = clk_core_set_parent_nolock(clk->core,
> parent ? parent->core : NULL);
> +
> + if (clk->protect_count)
> + clk_core_rate_protect(clk->core);
> +
> clk_prepare_unlock();
>
> return ret;
> @@ -1909,7 +2068,10 @@ static int clk_core_set_phase_nolock(struct clk_core *core, int degrees)
> if (!core)
> return 0;
>
> - trace_clk_set_phase(clk->core, degrees);
> + if (clk_core_rate_is_protected(core))
> + return -EBUSY;
> +
> + trace_clk_set_phase(core, degrees);
>
> if (core->ops->set_phase)
> ret = core->ops->set_phase(core->hw, degrees);
> @@ -1952,7 +2114,15 @@ int clk_set_phase(struct clk *clk, int degrees)
> degrees += 360;
>
> clk_prepare_lock();
> +
> + if (clk->protect_count)
> + clk_core_rate_unprotect(clk->core);
> +
> ret = clk_core_set_phase_nolock(clk->core, degrees);
> +
> + if (clk->protect_count)
> + clk_core_rate_protect(clk->core);
> +
> clk_prepare_unlock();
>
> return ret;
> @@ -2039,11 +2209,12 @@ static void clk_summary_show_one(struct seq_file *s, struct clk_core *c,
> if (!c)
> return;
>
> - seq_printf(s, "%*s%-*s %11d %12d %11lu %10lu %-3d\n",
> + seq_printf(s, "%*s%-*s %11d %12d %12d %11lu %10lu %-3d\n",
> level * 3 + 1, "",
> 30 - level * 3, c->name,
> - c->enable_count, c->prepare_count, clk_core_get_rate(c),
> - clk_core_get_accuracy(c), clk_core_get_phase(c));
> + c->enable_count, c->prepare_count, c->protect_count,
> + clk_core_get_rate(c), clk_core_get_accuracy(c),
> + clk_core_get_phase(c));
> }
>
> static void clk_summary_show_subtree(struct seq_file *s, struct clk_core *c,
> @@ -2065,8 +2236,8 @@ static int clk_summary_show(struct seq_file *s, void *data)
> struct clk_core *c;
> struct hlist_head **lists = (struct hlist_head **)s->private;
>
> - seq_puts(s, " clock enable_cnt prepare_cnt rate accuracy phase\n");
> - seq_puts(s, "----------------------------------------------------------------------------------------\n");
> + seq_puts(s, " clock enable_cnt prepare_cnt protect_cnt rate accuracy phase\n");
> + seq_puts(s, "----------------------------------------------------------------------------------------------------\n");
>
> clk_prepare_lock();
>
> @@ -2101,6 +2272,7 @@ static void clk_dump_one(struct seq_file *s, struct clk_core *c, int level)
> seq_printf(s, "\"%s\": { ", c->name);
> seq_printf(s, "\"enable_count\": %d,", c->enable_count);
> seq_printf(s, "\"prepare_count\": %d,", c->prepare_count);
> + seq_printf(s, "\"protect_count\": %d,", c->protect_count);
> seq_printf(s, "\"rate\": %lu,", clk_core_get_rate(c));
> seq_printf(s, "\"accuracy\": %lu,", clk_core_get_accuracy(c));
> seq_printf(s, "\"phase\": %d", clk_core_get_phase(c));
> @@ -2231,6 +2403,11 @@ static int clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
> if (!d)
> goto err_out;
>
> + d = debugfs_create_u32("clk_protect_count", S_IRUGO, core->dentry,
> + (u32 *)&core->protect_count);
> + if (!d)
> + goto err_out;
> +
> d = debugfs_create_u32("clk_notifier_count", S_IRUGO, core->dentry,
> (u32 *)&core->notifier_count);
> if (!d)
> @@ -2794,6 +2971,11 @@ void clk_unregister(struct clk *clk)
> if (clk->core->prepare_count)
> pr_warn("%s: unregistering prepared clock: %s\n",
> __func__, clk->core->name);
> +
> + if (clk->core->protect_count)
> + pr_warn("%s: unregistering protected clock: %s\n",
> + __func__, clk->core->name);
> +
> kref_put(&clk->core->ref, __clk_release);
> unlock:
> clk_prepare_unlock();
> @@ -2952,6 +3134,17 @@ void __clk_put(struct clk *clk)
>
> clk_prepare_lock();
>
> + /*
> + * Before calling clk_put, all calls to clk_rate_protect from a given
> + * user must be balanced with calls to clk_rate_unprotect and by that
> + * same user
> + */
> + WARN_ON(clk->protect_count);
> +
> + /* We voiced our concern, let's sanitize the situation */
> + for (; clk->protect_count; clk->protect_count--)
> + clk_core_rate_unprotect(clk->core);
> +
> hlist_del(&clk->clks_node);
> if (clk->min_rate > clk->core->req_rate ||
> clk->max_rate < clk->core->req_rate)
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index a428aec36ace..ebd7df5f375f 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -739,6 +739,7 @@ unsigned long clk_hw_get_rate(const struct clk_hw *hw);
> unsigned long __clk_get_flags(struct clk *clk);
> unsigned long clk_hw_get_flags(const struct clk_hw *hw);
> bool clk_hw_is_prepared(const struct clk_hw *hw);
> +bool clk_hw_rate_is_protected(const struct clk_hw *hw);
> bool clk_hw_is_enabled(const struct clk_hw *hw);
> bool __clk_is_enabled(struct clk *clk);
> struct clk *__clk_lookup(const char *name);
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index 024cd07870d0..85d73e02df40 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -265,6 +265,30 @@ struct clk *devm_clk_get(struct device *dev, const char *id);
> */
> struct clk *devm_get_clk_from_child(struct device *dev,
> struct device_node *np, const char *con_id);
> +/**
> + * clk_rate_protect - inform the system when the clock rate must be protected.
> + * @clk: clock source
> + *
> + * This function informs the system that the consumer protecting the clock
> + * depends on the rate of the clock source and can't tolerate any glitches
> + * introduced by further clock rate change or re-parenting of the clock source.
> + *
> + * Must not be called from within atomic context.
> + */
> +void clk_rate_protect(struct clk *clk);
> +
> +/**
> + * clk_rate_unprotect - release the protection of the clock source.
> + * @clk: clock source
> + *
> + * This function informs the system that the consumer previously protecting the
> + * clock rate can now deal with other consumer altering the clock source rate
> + *
> + * The caller must balance the number of rate_protect and rate_unprotect calls.
> + *
> + * Must not be called from within atomic context.
> + */
> +void clk_rate_unprotect(struct clk *clk);
>
> /**
> * clk_enable - inform the system when the clock source should be running.
> @@ -460,6 +484,11 @@ static inline void clk_put(struct clk *clk) {}
>
> static inline void devm_clk_put(struct device *dev, struct clk *clk) {}
>
> +
> +static inline void clk_protect(struct clk *clk) {}
> +
> +static inline void clk_unprotect(struct clk *clk) {}
> +
> static inline int clk_enable(struct clk *clk)
> {
> return 0;
> --
> 2.9.4
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-clk" in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
More information about the linux-amlogic
mailing list