Re: [PATCH 1/4] firmware: arm_scmi: bus: Bypass setting fwnode for scmi cpufreq

[Sudeep Holla <sudeep.holla@xxxxxxx>]

On Wed, Dec 25, 2024 at 04:20:44PM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@xxxxxxx>
>
> Two drivers scmi_cpufreq.c and scmi_perf_domain.c both use
> SCMI_PROTCOL_PERF protocol, but with different name, so two scmi devices
> will be created. But the fwnode->dev could only point to one device.
>
> If scmi cpufreq device created earlier, the fwnode->dev will point to
> the scmi cpufreq device. Then the fw_devlink will link performance
> domain user device(consumer) to the scmi cpufreq device(supplier).
> But actually the performance domain user device, such as GPU, should use
> the scmi perf device as supplier. Also if 'cpufreq.off=1' in bootargs,
> the GPU driver will defer probe always, because of the scmi cpufreq
> device not ready.
>
> Because for cpufreq, no need use fw_devlink. So bypass setting fwnode
> for scmi cpufreq device.
>
> Fixes: 96da4a99ce50 ("firmware: arm_scmi: Set fwnode for the scmi_device")
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> ---
>  drivers/firmware/arm_scmi/bus.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
> index 157172a5f2b577ce4f04425f967f548230c1ebed..12190d4dabb65484543044b4424fbe3b67245466 100644
> --- a/drivers/firmware/arm_scmi/bus.c
> +++ b/drivers/firmware/arm_scmi/bus.c
> @@ -345,6 +345,19 @@ static void __scmi_device_destroy(struct scmi_device *scmi_dev)
>  	device_unregister(&scmi_dev->dev);
>  }
>
> +static int
> +__scmi_device_set_node(struct scmi_device *scmi_dev, struct device_node *np,
> +		       int protocol, const char *name)
> +{
> +	/* cpufreq device does not need to be supplier from devlink perspective */
> +	if ((protocol == SCMI_PROTOCOL_PERF) && !strcmp(name, "cpufreq"))
> +		return 0;
>

This is just a assumption based on current implementation. What happens
if this is needed. Infact, it is used in the current implementation to
create a dummy clock provider, so for sure with this change that will
break IMO.

--
Regards,
Sudeep