[PATCH] clk: fixed-rate: Use "clock-output-names" to name fixed clocks

[Quentin Schulz]

Hi Fabio,

On 4/17/25 2:31 PM, Fabio Estevam wrote:
> From: Fabio Estevam <festevam at denx.de>
> 
> Currently, fixed-rate clocks in U-Boot are named based on their devicetree
> node names. For example, given the following node:
> 
> osc_24m: clock-osc-24m {
> 	compatible = "fixed-clock";
> 	#clock-cells = <0>;
> 	clock-frequency = <24000000>;
> 	clock-output-names = "osc_24m";
> };
> 
> U-Boot registers the clock as "clock-osc-24m", derived from the node name,
> ignoring the clock-output-names property.
> 
> This differs from Linux, which uses the clock-output-names property when
> assigning clock names. As a result, clock consumers expecting names
> like "osc_24m" (as defined in the property) may fail to resolve clocks
> correctly in U-Boot.
> 
> Update the fixed-rate clock driver to check for the clock-output-names
> property and use it as the clock name if present. If not, the fallback
> remains the node name. This makes U-Boot behavior consistent with Linux.
> 
> One concrete impact is on i.MX8MP, where USB clock lookup failed following
> commit b4734c9c333b ("clk: imx: Convert clock-osc-* back to osc_*").
> 
> With this change applied, fixed-clocks are correctly registered with their
> expected names:
> 
> u-boot=> clk dump
>   Rate               Usecnt      Name
> ------------------------------------------
>   32768                0        |-- osc_32k
>   24000000             5        |-- osc_24m
> 
> This change restores i.MX8MP USB functionality by ensuring the proper clock
> names are used.
> 
> Fixes: b4734c9c333b ("clk: imx: Convert clock-osc-* back to osc_*")
> Reported-by: Francesco Dolcini <francesco.dolcini at toradex.com>
> Signed-off-by: Fabio Estevam <festevam at denx.de>
> ---
>   drivers/clk/clk_fixed_rate.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/clk/clk_fixed_rate.c b/drivers/clk/clk_fixed_rate.c
> index d1da05cc18a5..7b89f9c80e95 100644
> --- a/drivers/clk/clk_fixed_rate.c
> +++ b/drivers/clk/clk_fixed_rate.c
> @@ -35,6 +35,8 @@ void clk_fixed_rate_ofdata_to_plat_(struct udevice *dev,
>   				    struct clk_fixed_rate *plat)
>   {
>   	struct clk *clk = &plat->clk;
> +	const char *clk_name;
> +
>   	if (CONFIG_IS_ENABLED(OF_REAL))
>   		plat->fixed_rate = dev_read_u32_default(dev, "clock-frequency",
>   							0);
> @@ -45,6 +47,16 @@ void clk_fixed_rate_ofdata_to_plat_(struct udevice *dev,
>   
>   	clk->dev = dev;
>   	clk->enable_count = 0;
> +
> +	/*
> +	 * If the "clock-output-names" property is present, use it
> +	 * as the clock name, like it is done in Linux.
> +	 * Otherwise, the original behavior will be preserved: the fixed clock
> +	 * name will be its node name.
> +	 *
> +	 */
> +	if (!(dev_read_string_index(dev, "clock-output-names", 0, &clk_name)))
> +		dev->name = clk_name;

What about

dev_read_string_index(dev, "clock-output-names", 0, &dev->name);

so you don't need to store the return value in a temporary variable?

Cheers,
Quentin