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

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Message-ID: <20241227151306.jh2oabc64xd54dms@bogus>
Date: Fri, 27 Dec 2024 15:13:06 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc: Cristian Marussi <cristian.marussi@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Saravana Kannan <saravanak@...gle.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Dong Aisheng <aisheng.dong@....com>,
	Fabio Estevam <festevam@...il.com>, Shawn Guo <shawnguo@...nel.org>,
	Jacky Bai <ping.bai@....com>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Sascha Hauer <s.hauer@...gutronix.de>, arm-scmi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org, imx@...ts.linux.dev,
	Peng Fan <peng.fan@....com>
Subject: Re: [PATCH 1/4] firmware: arm_scmi: bus: Bypass setting fwnode for
 scmi cpufreq

On Wed, Dec 25, 2024 at 04:20:44PM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@....com>
>
> 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@....com>
> ---
>  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