| Message ID | 1385556285-19180-2-git-send-email-b.brezillon@overkiz.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hello, On Wed, Nov 27, 2013 at 01:44:44PM +0100, Boris BREZILLON wrote: > The clock accuracy is expressed in ppb (parts per billion) and represents > the possible clock drift. > Say you have a clock (e.g. an oscillator) which provides a fixed clock of > 20MHz with an accuracy of +- 20Hz. This accuracy expressed in ppb is > 20Hz/20MHz = 1000 ppb (or 1 ppm). > > Clock users may need the clock accuracy information in order to choose > the best clock (the one with the best accuracy) across several available > clocks. > > This patch adds clk accuracy retrieval support for common clk framework by > means of a new function called clk_get_accuracy. > This function returns the given clock accuracy expressed in ppb. > > In order to get the clock accuracy, this implementation adds one callback > called recalc_accuracy to the clk_ops structure. > This callback is given the parent clock accuracy (if the clock is not a > root clock) and should recalculate the given clock accuracy. > > This callback is optional and may be implemented if the clock is not > a perfect clock (accuracy != 0 ppb). > > Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com> > --- > Documentation/clk.txt | 4 ++ > drivers/clk/clk.c | 109 ++++++++++++++++++++++++++++++++++++++++-- > include/linux/clk-private.h | 1 + > include/linux/clk-provider.h | 11 +++++ > include/linux/clk.h | 17 +++++++ > 5 files changed, 138 insertions(+), 4 deletions(-) > > diff --git a/Documentation/clk.txt b/Documentation/clk.txt > index 3aeb5c4..eb20198 100644 > --- a/Documentation/clk.txt > +++ b/Documentation/clk.txt > @@ -77,6 +77,8 @@ the operations defined in clk.h: > int (*set_parent)(struct clk_hw *hw, u8 index); > u8 (*get_parent)(struct clk_hw *hw); > int (*set_rate)(struct clk_hw *hw, unsigned long); > + unsigned long (*recalc_accuracy)(struct clk_hw *hw, > + unsigned long parent_accuracy); > void (*init)(struct clk_hw *hw); > }; > > @@ -202,6 +204,8 @@ optional or must be evaluated on a case-by-case basis. > .set_parent | | | n | y | n | > .get_parent | | | n | y | n | > | | | | | | > +.recalc_accuracy| | | | | | > + | | | | | | > .init | | | | | | > ----------------------------------------------------------- > [1] either one of round_rate or determine_rate is required. > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index 2cf2ea6..4b0c1bc 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -104,10 +104,11 @@ static void clk_summary_show_one(struct seq_file *s, struct clk *c, int level) > if (!c) > return; > > - seq_printf(s, "%*s%-*s %-11d %-12d %-10lu", > + seq_printf(s, "%*s%-*s %-11d %-12d %-10lu %-11lu", > level * 3 + 1, "", > 30 - level * 3, c->name, > - c->enable_count, c->prepare_count, clk_get_rate(c)); > + c->enable_count, c->prepare_count, clk_get_rate(c), > + clk_get_accuracy(c)); > seq_printf(s, "\n"); > } > > @@ -129,8 +130,8 @@ static int clk_summary_show(struct seq_file *s, void *data) > { > struct clk *c; > > - seq_printf(s, " clock enable_cnt prepare_cnt rate\n"); > - seq_printf(s, "---------------------------------------------------------------------\n"); > + seq_printf(s, " clock enable_cnt prepare_cnt rate accuracy\n"); > + seq_printf(s, "---------------------------------------------------------------------------------\n"); > > clk_prepare_lock(); > > @@ -167,6 +168,7 @@ static void clk_dump_one(struct seq_file *s, struct clk *c, int level) > seq_printf(s, "\"enable_count\": %d,", c->enable_count); > seq_printf(s, "\"prepare_count\": %d,", c->prepare_count); > seq_printf(s, "\"rate\": %lu", clk_get_rate(c)); > + seq_printf(s, "\"accuracy\": %lu", clk_get_accuracy(c)); > } > > static void clk_dump_subtree(struct seq_file *s, struct clk *c, int level) > @@ -248,6 +250,11 @@ static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry) > if (!d) > goto err_out; > > + d = debugfs_create_u32("clk_accuracy", S_IRUGO, clk->dentry, > + (u32 *)&clk->accuracy); > + if (!d) > + goto err_out; > + > d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry, > (u32 *)&clk->flags); > if (!d) > @@ -602,6 +609,28 @@ out: > return ret; > } > > +unsigned long __clk_get_accuracy(struct clk *clk) > +{ > + unsigned long ret; > + > + if (!clk) { > + ret = 0; > + goto out; > + } > + > + ret = clk->accuracy; > + > + if (clk->flags & CLK_IS_ROOT) > + goto out; > + > + if (!clk->parent) > + ret = 0; Why do you need this? Wouldn't it be enough to assert clk->accuracy being 0 in this case? > +out: > + return ret; > +} > +EXPORT_SYMBOL_GPL(__clk_get_accuracy); > + > unsigned long __clk_get_flags(struct clk *clk) > { > return !clk ? 0 : clk->flags; > @@ -1016,6 +1045,59 @@ static int __clk_notify(struct clk *clk, unsigned long msg, > } > > /** > + * __clk_recalc_accuracies > + * @clk: first clk in the subtree > + * @msg: notification type (see include/linux/clk.h) There is no msg parameter in this function. > + * Walks the subtree of clks starting with clk and recalculates accuracies as > + * it goes. Note that if a clk does not implement the .recalc_rate callback > + * then it is assumed that the clock will take on the rate of it's parent. > + * > + * Caller must hold prepare_lock. > + */ > +static void __clk_recalc_accuracies(struct clk *clk) > +{ > + unsigned long parent_accuracy = 0; > + struct clk *child; > + > + if (clk->parent) > + parent_accuracy = clk->parent->accuracy; > + > + if (clk->ops->recalc_accuracy) > + clk->accuracy = clk->ops->recalc_accuracy(clk->hw, > + parent_accuracy); > + else > + clk->accuracy = parent_accuracy; > + > + hlist_for_each_entry(child, &clk->children, child_node) > + __clk_recalc_accuracies(child); > +} > + > +/** > + * clk_get_accuracy - return the accuracy of clk > + * @clk: the clk whose accuracy is being returned > + * > + * Simply returns the cached accuracy of the clk, unless > + * CLK_GET_ACCURACY_NOCACHE flag is set, which means a recalc_rate will be > + * issued. > + * If clk is NULL then returns 0. > + */ > +long clk_get_accuracy(struct clk *clk) > +{ > + unsigned long accuracy; > + > + clk_prepare_lock(); > + if (clk && (clk->flags & CLK_GET_ACCURACY_NOCACHE)) > + __clk_recalc_accuracies(clk); > + > + accuracy = __clk_get_accuracy(clk); > + clk_prepare_unlock(); > + > + return accuracy; > +} > +EXPORT_SYMBOL_GPL(clk_get_accuracy); > + > +/** > * __clk_recalc_rates > * @clk: first clk in the subtree > * @msg: notification type (see include/linux/clk.h) > @@ -1551,6 +1633,7 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent) > { > clk_reparent(clk, new_parent); > clk_debug_reparent(clk, new_parent); > + __clk_recalc_accuracies(clk); > __clk_recalc_rates(clk, POST_RATE_CHANGE); > } > > @@ -1621,6 +1704,9 @@ int clk_set_parent(struct clk *clk, struct clk *parent) > /* do the re-parent */ > ret = __clk_set_parent(clk, parent, p_index); > > + /* propagate accuracy recalculation */ > + __clk_recalc_accuracies(clk); > + Would it make sense to move this call into the if (ret) below? The rate is only recalculated there, too. > /* propagate rate recalculation accordingly */ > if (ret) > __clk_recalc_rates(clk, ABORT_RATE_CHANGE); Best regards Uwe
Hello Uwe, Le 02/12/2013 08:50, Uwe Kleine-König a écrit : > Hello, > > On Wed, Nov 27, 2013 at 01:44:44PM +0100, Boris BREZILLON wrote: >> The clock accuracy is expressed in ppb (parts per billion) and represents >> the possible clock drift. >> Say you have a clock (e.g. an oscillator) which provides a fixed clock of >> 20MHz with an accuracy of +- 20Hz. This accuracy expressed in ppb is >> 20Hz/20MHz = 1000 ppb (or 1 ppm). >> >> Clock users may need the clock accuracy information in order to choose >> the best clock (the one with the best accuracy) across several available >> clocks. >> >> This patch adds clk accuracy retrieval support for common clk framework by >> means of a new function called clk_get_accuracy. >> This function returns the given clock accuracy expressed in ppb. >> >> In order to get the clock accuracy, this implementation adds one callback >> called recalc_accuracy to the clk_ops structure. >> This callback is given the parent clock accuracy (if the clock is not a >> root clock) and should recalculate the given clock accuracy. >> >> This callback is optional and may be implemented if the clock is not >> a perfect clock (accuracy != 0 ppb). >> >> Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com> >> --- >> Documentation/clk.txt | 4 ++ >> drivers/clk/clk.c | 109 ++++++++++++++++++++++++++++++++++++++++-- >> include/linux/clk-private.h | 1 + >> include/linux/clk-provider.h | 11 +++++ >> include/linux/clk.h | 17 +++++++ >> 5 files changed, 138 insertions(+), 4 deletions(-) >> >> diff --git a/Documentation/clk.txt b/Documentation/clk.txt >> index 3aeb5c4..eb20198 100644 >> --- a/Documentation/clk.txt >> +++ b/Documentation/clk.txt >> @@ -77,6 +77,8 @@ the operations defined in clk.h: >> int (*set_parent)(struct clk_hw *hw, u8 index); >> u8 (*get_parent)(struct clk_hw *hw); >> int (*set_rate)(struct clk_hw *hw, unsigned long); >> + unsigned long (*recalc_accuracy)(struct clk_hw *hw, >> + unsigned long parent_accuracy); >> void (*init)(struct clk_hw *hw); >> }; >> >> @@ -202,6 +204,8 @@ optional or must be evaluated on a case-by-case basis. >> .set_parent | | | n | y | n | >> .get_parent | | | n | y | n | >> | | | | | | >> +.recalc_accuracy| | | | | | >> + | | | | | | >> .init | | | | | | >> ----------------------------------------------------------- >> [1] either one of round_rate or determine_rate is required. >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c >> index 2cf2ea6..4b0c1bc 100644 >> --- a/drivers/clk/clk.c >> +++ b/drivers/clk/clk.c >> @@ -104,10 +104,11 @@ static void clk_summary_show_one(struct seq_file *s, struct clk *c, int level) >> if (!c) >> return; >> >> - seq_printf(s, "%*s%-*s %-11d %-12d %-10lu", >> + seq_printf(s, "%*s%-*s %-11d %-12d %-10lu %-11lu", >> level * 3 + 1, "", >> 30 - level * 3, c->name, >> - c->enable_count, c->prepare_count, clk_get_rate(c)); >> + c->enable_count, c->prepare_count, clk_get_rate(c), >> + clk_get_accuracy(c)); >> seq_printf(s, "\n"); >> } >> >> @@ -129,8 +130,8 @@ static int clk_summary_show(struct seq_file *s, void *data) >> { >> struct clk *c; >> >> - seq_printf(s, " clock enable_cnt prepare_cnt rate\n"); >> - seq_printf(s, "---------------------------------------------------------------------\n"); >> + seq_printf(s, " clock enable_cnt prepare_cnt rate accuracy\n"); >> + seq_printf(s, "---------------------------------------------------------------------------------\n"); >> >> clk_prepare_lock(); >> >> @@ -167,6 +168,7 @@ static void clk_dump_one(struct seq_file *s, struct clk *c, int level) >> seq_printf(s, "\"enable_count\": %d,", c->enable_count); >> seq_printf(s, "\"prepare_count\": %d,", c->prepare_count); >> seq_printf(s, "\"rate\": %lu", clk_get_rate(c)); >> + seq_printf(s, "\"accuracy\": %lu", clk_get_accuracy(c)); >> } >> >> static void clk_dump_subtree(struct seq_file *s, struct clk *c, int level) >> @@ -248,6 +250,11 @@ static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry) >> if (!d) >> goto err_out; >> >> + d = debugfs_create_u32("clk_accuracy", S_IRUGO, clk->dentry, >> + (u32 *)&clk->accuracy); >> + if (!d) >> + goto err_out; >> + >> d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry, >> (u32 *)&clk->flags); >> if (!d) >> @@ -602,6 +609,28 @@ out: >> return ret; >> } >> >> +unsigned long __clk_get_accuracy(struct clk *clk) >> +{ >> + unsigned long ret; >> + >> + if (!clk) { >> + ret = 0; >> + goto out; >> + } >> + >> + ret = clk->accuracy; >> + >> + if (clk->flags & CLK_IS_ROOT) >> + goto out; >> + >> + if (!clk->parent) >> + ret = 0; > Why do you need this? Wouldn't it be enough to assert clk->accuracy > being 0 in this case? I'm not sure. I did this because it was done this way for __clk_get_rate (which is not a valid argument ;)). Now that I think about it I don't find any good reason for not directly returning the clk->accuracy (even if the clk is orphan). I mean, if we consider the parent_clk as perfect (which is the case if the clk is orphan), then the child clk might still introduce some inaccuracy. And I think it's better to return the maximum clk accuracy instead of considering the clk is perfect. I'll fix this in the next version. >> +out: >> + return ret; >> +} >> +EXPORT_SYMBOL_GPL(__clk_get_accuracy); >> + >> unsigned long __clk_get_flags(struct clk *clk) >> { >> return !clk ? 0 : clk->flags; >> @@ -1016,6 +1045,59 @@ static int __clk_notify(struct clk *clk, unsigned long msg, >> } >> >> /** >> + * __clk_recalc_accuracies >> + * @clk: first clk in the subtree >> + * @msg: notification type (see include/linux/clk.h) > There is no msg parameter in this function. I'll fix the comment. > >> + * Walks the subtree of clks starting with clk and recalculates accuracies as >> + * it goes. Note that if a clk does not implement the .recalc_rate callback >> + * then it is assumed that the clock will take on the rate of it's parent. >> + * >> + * Caller must hold prepare_lock. >> + */ >> +static void __clk_recalc_accuracies(struct clk *clk) >> +{ >> + unsigned long parent_accuracy = 0; >> + struct clk *child; >> + >> + if (clk->parent) >> + parent_accuracy = clk->parent->accuracy; >> + >> + if (clk->ops->recalc_accuracy) >> + clk->accuracy = clk->ops->recalc_accuracy(clk->hw, >> + parent_accuracy); >> + else >> + clk->accuracy = parent_accuracy; >> + >> + hlist_for_each_entry(child, &clk->children, child_node) >> + __clk_recalc_accuracies(child); >> +} >> + >> +/** >> + * clk_get_accuracy - return the accuracy of clk >> + * @clk: the clk whose accuracy is being returned >> + * >> + * Simply returns the cached accuracy of the clk, unless >> + * CLK_GET_ACCURACY_NOCACHE flag is set, which means a recalc_rate will be >> + * issued. >> + * If clk is NULL then returns 0. >> + */ >> +long clk_get_accuracy(struct clk *clk) >> +{ >> + unsigned long accuracy; >> + >> + clk_prepare_lock(); >> + if (clk && (clk->flags & CLK_GET_ACCURACY_NOCACHE)) >> + __clk_recalc_accuracies(clk); >> + >> + accuracy = __clk_get_accuracy(clk); >> + clk_prepare_unlock(); >> + >> + return accuracy; >> +} >> +EXPORT_SYMBOL_GPL(clk_get_accuracy); >> + >> +/** >> * __clk_recalc_rates >> * @clk: first clk in the subtree >> * @msg: notification type (see include/linux/clk.h) >> @@ -1551,6 +1633,7 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent) >> { >> clk_reparent(clk, new_parent); >> clk_debug_reparent(clk, new_parent); >> + __clk_recalc_accuracies(clk); >> __clk_recalc_rates(clk, POST_RATE_CHANGE); >> } >> >> @@ -1621,6 +1704,9 @@ int clk_set_parent(struct clk *clk, struct clk *parent) >> /* do the re-parent */ >> ret = __clk_set_parent(clk, parent, p_index); >> >> + /* propagate accuracy recalculation */ >> + __clk_recalc_accuracies(clk); >> + > Would it make sense to move this call into the if (ret) below? The rate > is only recalculated there, too. You mean only if __clk_set_parent returns 0. Yes it makes sense: the accuracy should not change if the parent hasn't changed (is this case, if we fail to change the parent). BTW, the rate is recalculated anyway, the only thing that changes is the notification message. I'll fix this if no ones finds a good reason to recalculate the accuracy when we fail to change the parent. Thanks for your review Best Regars, Boris >> /* propagate rate recalculation accordingly */ >> if (ret) >> __clk_recalc_rates(clk, ABORT_RATE_CHANGE); > Best regards > Uwe >
diff --git a/Documentation/clk.txt b/Documentation/clk.txt index 3aeb5c4..eb20198 100644 --- a/Documentation/clk.txt +++ b/Documentation/clk.txt @@ -77,6 +77,8 @@ the operations defined in clk.h: int (*set_parent)(struct clk_hw *hw, u8 index); u8 (*get_parent)(struct clk_hw *hw); int (*set_rate)(struct clk_hw *hw, unsigned long); + unsigned long (*recalc_accuracy)(struct clk_hw *hw, + unsigned long parent_accuracy); void (*init)(struct clk_hw *hw); }; @@ -202,6 +204,8 @@ optional or must be evaluated on a case-by-case basis. .set_parent | | | n | y | n | .get_parent | | | n | y | n | | | | | | | +.recalc_accuracy| | | | | | + | | | | | | .init | | | | | | ----------------------------------------------------------- [1] either one of round_rate or determine_rate is required. diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 2cf2ea6..4b0c1bc 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -104,10 +104,11 @@ static void clk_summary_show_one(struct seq_file *s, struct clk *c, int level) if (!c) return; - seq_printf(s, "%*s%-*s %-11d %-12d %-10lu", + seq_printf(s, "%*s%-*s %-11d %-12d %-10lu %-11lu", level * 3 + 1, "", 30 - level * 3, c->name, - c->enable_count, c->prepare_count, clk_get_rate(c)); + c->enable_count, c->prepare_count, clk_get_rate(c), + clk_get_accuracy(c)); seq_printf(s, "\n"); } @@ -129,8 +130,8 @@ static int clk_summary_show(struct seq_file *s, void *data) { struct clk *c; - seq_printf(s, " clock enable_cnt prepare_cnt rate\n"); - seq_printf(s, "---------------------------------------------------------------------\n"); + seq_printf(s, " clock enable_cnt prepare_cnt rate accuracy\n"); + seq_printf(s, "---------------------------------------------------------------------------------\n"); clk_prepare_lock(); @@ -167,6 +168,7 @@ static void clk_dump_one(struct seq_file *s, struct clk *c, int level) seq_printf(s, "\"enable_count\": %d,", c->enable_count); seq_printf(s, "\"prepare_count\": %d,", c->prepare_count); seq_printf(s, "\"rate\": %lu", clk_get_rate(c)); + seq_printf(s, "\"accuracy\": %lu", clk_get_accuracy(c)); } static void clk_dump_subtree(struct seq_file *s, struct clk *c, int level) @@ -248,6 +250,11 @@ static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry) if (!d) goto err_out; + d = debugfs_create_u32("clk_accuracy", S_IRUGO, clk->dentry, + (u32 *)&clk->accuracy); + if (!d) + goto err_out; + d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry, (u32 *)&clk->flags); if (!d) @@ -602,6 +609,28 @@ out: return ret; } +unsigned long __clk_get_accuracy(struct clk *clk) +{ + unsigned long ret; + + if (!clk) { + ret = 0; + goto out; + } + + ret = clk->accuracy; + + if (clk->flags & CLK_IS_ROOT) + goto out; + + if (!clk->parent) + ret = 0; + +out: + return ret; +} +EXPORT_SYMBOL_GPL(__clk_get_accuracy); + unsigned long __clk_get_flags(struct clk *clk) { return !clk ? 0 : clk->flags; @@ -1016,6 +1045,59 @@ static int __clk_notify(struct clk *clk, unsigned long msg, } /** + * __clk_recalc_accuracies + * @clk: first clk in the subtree + * @msg: notification type (see include/linux/clk.h) + * + * Walks the subtree of clks starting with clk and recalculates accuracies as + * it goes. Note that if a clk does not implement the .recalc_rate callback + * then it is assumed that the clock will take on the rate of it's parent. + * + * Caller must hold prepare_lock. + */ +static void __clk_recalc_accuracies(struct clk *clk) +{ + unsigned long parent_accuracy = 0; + struct clk *child; + + if (clk->parent) + parent_accuracy = clk->parent->accuracy; + + if (clk->ops->recalc_accuracy) + clk->accuracy = clk->ops->recalc_accuracy(clk->hw, + parent_accuracy); + else + clk->accuracy = parent_accuracy; + + hlist_for_each_entry(child, &clk->children, child_node) + __clk_recalc_accuracies(child); +} + +/** + * clk_get_accuracy - return the accuracy of clk + * @clk: the clk whose accuracy is being returned + * + * Simply returns the cached accuracy of the clk, unless + * CLK_GET_ACCURACY_NOCACHE flag is set, which means a recalc_rate will be + * issued. + * If clk is NULL then returns 0. + */ +long clk_get_accuracy(struct clk *clk) +{ + unsigned long accuracy; + + clk_prepare_lock(); + if (clk && (clk->flags & CLK_GET_ACCURACY_NOCACHE)) + __clk_recalc_accuracies(clk); + + accuracy = __clk_get_accuracy(clk); + clk_prepare_unlock(); + + return accuracy; +} +EXPORT_SYMBOL_GPL(clk_get_accuracy); + +/** * __clk_recalc_rates * @clk: first clk in the subtree * @msg: notification type (see include/linux/clk.h) @@ -1551,6 +1633,7 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent) { clk_reparent(clk, new_parent); clk_debug_reparent(clk, new_parent); + __clk_recalc_accuracies(clk); __clk_recalc_rates(clk, POST_RATE_CHANGE); } @@ -1621,6 +1704,9 @@ int clk_set_parent(struct clk *clk, struct clk *parent) /* do the re-parent */ ret = __clk_set_parent(clk, parent, p_index); + /* propagate accuracy recalculation */ + __clk_recalc_accuracies(clk); + /* propagate rate recalculation accordingly */ if (ret) __clk_recalc_rates(clk, ABORT_RATE_CHANGE); @@ -1730,6 +1816,21 @@ int __clk_init(struct device *dev, struct clk *clk) hlist_add_head(&clk->child_node, &clk_orphan_list); /* + * Set clk's accuracy. The preferred method is to use + * .recalc_accuracy. For simple clocks and lazy developers the default + * fallback is to use the parent's accuracy. If a clock doesn't have a + * parent (or is orphaned) then accuracy is set to zero (perfect + * clock). + */ + if (clk->ops->recalc_accuracy) + clk->accuracy = clk->ops->recalc_accuracy(clk->hw, + __clk_get_accuracy(clk->parent)); + else if (clk->parent) + clk->accuracy = clk->parent->accuracy; + else + clk->accuracy = 0; + + /* * Set clk's rate. The preferred method is to use .recalc_rate. For * simple clocks and lazy developers the default fallback is to use the * parent's rate. If a clock doesn't have a parent (or is orphaned) diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h index 8138c94..accb517 100644 --- a/include/linux/clk-private.h +++ b/include/linux/clk-private.h @@ -41,6 +41,7 @@ struct clk { unsigned long flags; unsigned int enable_count; unsigned int prepare_count; + unsigned long accuracy; struct hlist_head children; struct hlist_node child_node; unsigned int notifier_count; diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index 7e59253..16d182c 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -29,6 +29,7 @@ #define CLK_IS_BASIC BIT(5) /* Basic clk, can't do a to_clk_foo() */ #define CLK_GET_RATE_NOCACHE BIT(6) /* do not use the cached clk rate */ #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate change */ +#define CLK_GET_ACCURACY_NOCACHE BIT(8) /* do not use the cached clk accuracy */ struct clk_hw; @@ -108,6 +109,13 @@ struct clk_hw; * which is likely helpful for most .set_rate implementation. * Returns 0 on success, -EERROR otherwise. * + * @recalc_accuracy: Recalculate the accuracy of this clock. The clock accuracy + * is expressed in ppb (parts per billion). The parent accuracy is + * an input parameter. + * Returns the calculated accuracy. Optional - if this op is not + * set then clock accuracy will be initialized to parent accuracy + * or 0 (perfect clock) if clock has no parent. + * * The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow * implementations to split any work between atomic (enable) and sleepable * (prepare) contexts. If enabling a clock requires code that might sleep, @@ -139,6 +147,8 @@ struct clk_ops { u8 (*get_parent)(struct clk_hw *hw); int (*set_rate)(struct clk_hw *hw, unsigned long, unsigned long); + unsigned long (*recalc_accuracy)(struct clk_hw *hw, + unsigned long parent_accuracy); void (*init)(struct clk_hw *hw); }; @@ -433,6 +443,7 @@ struct clk *clk_get_parent_by_index(struct clk *clk, u8 index); unsigned int __clk_get_enable_count(struct clk *clk); unsigned int __clk_get_prepare_count(struct clk *clk); unsigned long __clk_get_rate(struct clk *clk); +unsigned long __clk_get_accuracy(struct clk *clk); unsigned long __clk_get_flags(struct clk *clk); bool __clk_is_prepared(struct clk *clk); bool __clk_is_enabled(struct clk *clk); diff --git a/include/linux/clk.h b/include/linux/clk.h index 9a6d045..0dd9114 100644 --- a/include/linux/clk.h +++ b/include/linux/clk.h @@ -82,6 +82,23 @@ int clk_notifier_register(struct clk *clk, struct notifier_block *nb); int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb); +/** + * clk_get_accuracy - obtain the clock accuracy in ppb (parts per billion) + * for a clock source. + * @clk: clock source + * + * This gets the clock source accuracy expressed in ppb. + * A perfect clock returns 0. + */ +long clk_get_accuracy(struct clk *clk); + +#else + +static inline long clk_get_accuracy(struct clk *clk) +{ + return -ENOTSUPP; +} + #endif /**
The clock accuracy is expressed in ppb (parts per billion) and represents the possible clock drift. Say you have a clock (e.g. an oscillator) which provides a fixed clock of 20MHz with an accuracy of +- 20Hz. This accuracy expressed in ppb is 20Hz/20MHz = 1000 ppb (or 1 ppm). Clock users may need the clock accuracy information in order to choose the best clock (the one with the best accuracy) across several available clocks. This patch adds clk accuracy retrieval support for common clk framework by means of a new function called clk_get_accuracy. This function returns the given clock accuracy expressed in ppb. In order to get the clock accuracy, this implementation adds one callback called recalc_accuracy to the clk_ops structure. This callback is given the parent clock accuracy (if the clock is not a root clock) and should recalculate the given clock accuracy. This callback is optional and may be implemented if the clock is not a perfect clock (accuracy != 0 ppb). Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com> --- Documentation/clk.txt | 4 ++ drivers/clk/clk.c | 109 ++++++++++++++++++++++++++++++++++++++++-- include/linux/clk-private.h | 1 + include/linux/clk-provider.h | 11 +++++ include/linux/clk.h | 17 +++++++ 5 files changed, 138 insertions(+), 4 deletions(-)