[PATCH 1/1] clk: introduce of_clk_detect_critical helper

[Maxim Kochetkov]

12.08.2025 19:41, Christian Marangi wrote:
> On Tue, Aug 12, 2025 at 07:29:46PM +0300, Maxim Kochetkov wrote:
>> This helper find clock-critiacl property in dts and assign
> 
> clock-critiacl -> typo


Thanks. Will fix it in v2

> 
>> CLK_IS_CRITICAL flag to the clock.
>>
>> Signed-off-by: Maxim Kochetkov <fido_max at inbox.ru>
>> ---
>>   drivers/clk/clk-uclass.c | 17 +++++++++++++++++
>>   drivers/core/of_access.c | 22 ++++++++++++++++++++++
>>   include/clk.h            | 28 ++++++++++++++++++++++++++++
>>   include/dm/of_access.h   | 17 +++++++++++++++++
>>   4 files changed, 84 insertions(+)
>>
>> diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c
>> index 7262e89b512..4f35b90382f 100644
>> --- a/drivers/clk/clk-uclass.c
>> +++ b/drivers/clk/clk-uclass.c
>> @@ -835,6 +835,23 @@ struct clk *devm_clk_get(struct udevice *dev, const char *id)
>>   	return clk;
>>   }
>>   
>> +int of_clk_detect_critical(struct device_node *np, int index,
>> +			   unsigned long *flags)
>> +{
>> +	struct property *prop;
>> +	const __be32 *cur;
>> +	uint32_t idx;
>> +
>> +	if (!np || !flags)
>> +		return -EINVAL;
>> +
>> +	of_property_for_each_u32(np, "clock-critical", prop, cur, idx)
>> +		if (index == idx)
>> +			*flags |= CLK_IS_CRITICAL;
>> +
>> +	return 0;
>> +}
>> +
>>   int clk_uclass_post_probe(struct udevice *dev)
>>   {
>>   	/*
>> diff --git a/drivers/core/of_access.c b/drivers/core/of_access.c
>> index b11e36202c1..59dda3ae152 100644
>> --- a/drivers/core/of_access.c
>> +++ b/drivers/core/of_access.c
>> @@ -666,6 +666,28 @@ int of_property_read_string_helper(const struct device_node *np,
>>   	return i <= 0 ? -ENODATA : i;
>>   }
>>   
>> +const __be32 *of_prop_next_u32(struct property *prop, const __be32 *cur,
>> +			       u32 *pu)
>> +{
>> +	const void *curv = cur;
>> +
>> +	if (!prop)
>> +		return NULL;
>> +
>> +	if (!cur) {
>> +		curv = prop->value;
>> +		goto out_val;
>> +	}
>> +
>> +	curv += sizeof(*cur);
>> +	if (curv >= prop->value + prop->length)
>> +		return NULL;
>> +
>> +out_val:
>> +	*pu = be32_to_cpup(curv);
>> +	return curv;
>> +}
>> +
>>   static int __of_root_parse_phandle_with_args(struct device_node *root,
>>   					     const struct device_node *np,
>>   					     const char *list_name,
>> diff --git a/include/clk.h b/include/clk.h
>> index f94135ff778..ea708f54fd5 100644
>> --- a/include/clk.h
>> +++ b/include/clk.h
>> @@ -589,6 +589,27 @@ bool clk_dev_binded(struct clk *clk);
>>    */
>>   ulong clk_get_id(const struct clk *clk);
>>   
>> +/**
>> + * of_clk_detect_critical() - set CLK_IS_CRITICAL flag from Device Tree
>> + * @np: Device node pointer associated with clock provider
>> + * @index: clock index
>> + * @flags: pointer to top-level framework flags
>> + *
>> + * Detects if the clock-critical property exists and, if so, sets the
>> + * corresponding CLK_IS_CRITICAL flag.
>> + *
>> + * Do not use this function. It exists only for legacy Device Tree
>> + * bindings, such as the one-clock-per-node style that are outdated.
>> + * Those bindings typically put all clock data into .dts and the Linux
>> + * driver has no clock data, thus making it impossible to set this flag
>> + * correctly from the driver. Only those drivers may call
>> + * of_clk_detect_critical from their setup functions.
>> + *
>> + * Return: error code or zero on success
>> + */
>> +int of_clk_detect_critical(struct device_node *np, int index,
>> +			   unsigned long *flags);
>> +
>>   #else /* CONFIG_IS_ENABLED(CLK) */
>>   
>>   static inline int clk_request(struct udevice *dev, struct clk *clk)
>> @@ -665,6 +686,13 @@ static inline ulong clk_get_id(const struct clk *clk)
>>   {
>>   	return 0;
>>   }
>> +
>> +int of_clk_detect_critical(struct device_node *np, int index,
>> +			   unsigned long *flags)
>> +{
>> +	return 0;
>> +}
>> +
>>   #endif /* CONFIG_IS_ENABLED(CLK) */
>>   
>>   /**
>> diff --git a/include/dm/of_access.h b/include/dm/of_access.h
>> index 44143a5a391..dba725498f5 100644
>> --- a/include/dm/of_access.h
>> +++ b/include/dm/of_access.h
>> @@ -405,6 +405,17 @@ int of_property_read_string_helper(const struct device_node *np,
>>   				   const char *propname, const char **out_strs,
>>   				   size_t sz, int index);
>>   
>> +/*
>> + * struct property *prop;
>> + * const __be32 *p;
>> + * u32 u;
>> + *
>> + * of_property_for_each_u32(np, "propname", prop, p, u)
>> + *         printk("U32 value: %x\n", u);
>> + */
>> +const __be32 *of_prop_next_u32(struct property *prop, const __be32 *cur,
>> +			       u32 *pu);
>> +
>>   /**
>>    * of_property_read_string_index() - Find and read a string from a multiple
>>    * strings property.
>> @@ -701,4 +712,10 @@ int of_remove_property(struct device_node *np, struct property *prop);
>>    */
>>   int of_remove_node(struct device_node *to_remove);
>>   
>> +#define of_property_for_each_u32(np, propname, prop, p, u)	\
>> +	for (prop = of_find_property(np, propname, NULL),	\
>> +		p = of_prop_next_u32(prop, NULL, &u);		\
>> +		p;						\
>> +		p = of_prop_next_u32(prop, p, &u))
>> +
>>   #endif
>> -- 
> 
> I would split these of additional function to a separate commit also
> where they come from? They are ported from Linux Kernel?

Ok, I will split it.
Yes these function are ported from Linux Kernel.

> 
> Also would be ideal to have some scenario where it's needed to declare a
> clock in DT that is critical. Isn't that handled directly by the clock
> driver internally?
> 

Yes. Now we can use this property from DT by custom drivers to mark 
critical clocks.