[PATCH] clk: Do not return signed value from clk_get_rate()

[David Lechner]

On 12/17/25 5:37 AM, Michal Simek wrote:
> As it is visible clk_get_rate() is returning ulong:
> ulong clk_get_rate(struct clk *clk);
> 
> Also struct clk_ops is defining it as
> ulong (*get_rate)(struct clk *clk);
> 
> That's why return 0 rate when ops->get_rate is not implemented which is
> the same value as is return when clock is not valid.
> 
> Signed-off-by: Michal Simek <michal.simek at amd.com>
> ---
> 
> Another alternative is obviously also return only long and fix all
> get_rate calls.

I noticed this oddness too recently while working on some clock
drivers. I suspect most people don't realize that clk get rate
functions can return an error because the type is unsigned and
they don't read the documentation. The driver I was working on
had a number of bugs due to this.

Changing the type to signed seems sensible. But I do wonder if there
are some GHz clock rates > INT_MAX on 32-bit platforms. Changing the
type could be problematic in that case.

If that is the case, the next best thing could be something
similar to IS_ERR() and PTR_ERR() for checking the return value
of clk rate functions, e.g RATE_IS_ERR() and RATE_ERR().

> ---
>  drivers/clk/clk-uclass.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c
> index 4420651f765c..bca818530d4c 100644
> --- a/drivers/clk/clk-uclass.c
> +++ b/drivers/clk/clk-uclass.c
> @@ -490,7 +490,7 @@ ulong clk_get_rate(struct clk *clk)
>  	ops = clk_dev_ops(clk->dev);
>  
>  	if (!ops->get_rate)
> -		return -ENOSYS;

There are a number of places checking rates for this return value
so I think changing it could unintentionally break things.

> +		return 0;
>  
>  	return ops->get_rate(clk);
>  }