On Thu, Apr 17, 2025 at 7:32 AM Fabio Estevam <feste...@gmail.com> wrote:
>
> From: Fabio Estevam <feste...@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.
You read my mind! I just sent out an e-mail to the other thread with
this very suggestion.
>
> 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.
Agreed.
>
> 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.
Tested-by: Adam Ford <aford...@gmail.com> #imx8mp-beacon
>
> Fixes: b4734c9c333b ("clk: imx: Convert clock-osc-* back to osc_*")
> Reported-by: Francesco Dolcini <francesco.dolc...@toradex.com>
> Signed-off-by: Fabio Estevam <feste...@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;
> }
>
> static ulong clk_fixed_rate_raw_get_rate(struct clk *clk)
> --
> 2.34.1
>
