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clk: Introduce clk_has_parent()
This new function is similar to clk_set_parent(), except that it doesn't actually change the parent. It merely checks that the given parent clock can be a parent for the given clock. A situation where this is useful is to check that a particular setup is valid before switching to it. One specific use-case for this is atomic modesetting in the DRM framework where setting a mode is divided into a check phase where a given configuration is validated before applying changes to the hardware. Cc: Russell King <linux@arm.linux.org.uk> Signed-off-by: Thierry Reding <treding@nvidia.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Michael Turquette <mturquette@linaro.org>
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@ -1651,6 +1651,36 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent)
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__clk_recalc_rates(clk, POST_RATE_CHANGE);
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}
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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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* @parent: parent clock source
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*
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* This function can be used in drivers that need to check that a clock can be
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* the parent of another without actually changing the parent.
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*
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* Returns true if @parent is a possible parent for @clk, false otherwise.
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*/
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bool clk_has_parent(struct clk *clk, struct clk *parent)
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{
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unsigned int i;
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/* NULL clocks should be nops, so return success if either is NULL. */
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if (!clk || !parent)
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return true;
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/* Optimize for the case where the parent is already the parent. */
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if (clk->parent == parent)
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return true;
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for (i = 0; i < clk->num_parents; i++)
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if (strcmp(clk->parent_names[i], parent->name) == 0)
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return true;
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return false;
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}
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EXPORT_SYMBOL_GPL(clk_has_parent);
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/**
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* clk_set_parent - switch the parent of a mux clk
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* @clk: the mux clk whose input we are switching
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@ -301,6 +301,18 @@ long clk_round_rate(struct clk *clk, unsigned long rate);
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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_has_parent - check if a clock is a possible parent for another
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* @clk: clock source
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* @parent: parent clock source
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*
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* This function can be used in drivers that need to check that a clock can be
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* the parent of another without actually changing the parent.
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*
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* Returns true if @parent is a possible parent for @clk, false otherwise.
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*/
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bool clk_has_parent(struct clk *clk, struct clk *parent);
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/**
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* clk_set_parent - set the parent clock source for this clock
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* @clk: clock source
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@ -374,6 +386,11 @@ static inline long clk_round_rate(struct clk *clk, unsigned long rate)
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return 0;
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}
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static inline bool clk_has_parent(struct clk *clk, struct clk *parent)
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{
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return true;
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}
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static inline int clk_set_parent(struct clk *clk, struct clk *parent)
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{
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return 0;
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