linux-kernel - Re: [PATCH 4/5] cpufreq: Add cpufreq driver for the RISC-V RPMI performance service group

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Message-ID: <CABdD5xmVVkQu6rYzF52V-JrsdL=NOQa9N9i8PsMgfaOh3GT-Bg@mail.gmail.com>
Date: Mon, 12 Jan 2026 16:17:59 +0530
From: Rahul Pathak <rahul@...mations.net>
To: Joshua Yeong <joshua.yeong@...rfivetech.com>
Cc: anup@...infault.org, leyfoon.tan@...rfivetech.com, robh@...nel.org, 
	krzk+dt@...nel.org, conor+dt@...nel.org, pjw@...nel.org, palmer@...belt.com, 
	aou@...s.berkeley.edu, alex@...ti.fr, rafael@...nel.org, 
	viresh.kumar@...aro.org, sboyd@...nel.org, jms@....tenstorrent.com, 
	darshan.prajapati@...fochips.com, charlie@...osinc.com, 
	dfustini@....tenstorrent.com, michal.simek@....com, cyy@...self.name, 
	jassisinghbrar@...il.com, andriy.shevchenko@...ux.intel.com, 
	linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 4/5] cpufreq: Add cpufreq driver for the RISC-V RPMI
 performance service group

> +
> +static int rpmi_cpufreq_probe(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +       struct rpmi_perf *mpxy_perf;
> +       struct rpmi_ctx *mpxy_ctx;
> +       int num_domains = 0;
> +       int ret, i;
> +
> +       mpxy_ctx = devm_kzalloc(&pdev->dev, sizeof(*mpxy_ctx), GFP_KERNEL);
> +       if (!mpxy_ctx)
> +               return -ENOMEM;
> +
> +       /* Setup mailbox client */
> +       mpxy_ctx->client.dev            = dev;
> +       mpxy_ctx->client.rx_callback    = NULL;
> +       mpxy_ctx->client.tx_block       = false;
> +       mpxy_ctx->client.knows_txdone   = true;
> +       mpxy_ctx->client.tx_tout        = 0;
> +
> +       /* Request mailbox channel */
> +       mpxy_ctx->chan = mbox_request_channel(&mpxy_ctx->client, 0);
> +       if (IS_ERR(mpxy_ctx->chan))
> +               return PTR_ERR(mpxy_ctx->chan);
> +
> +       ret = rpmi_cpufreq_attr_setup(dev, mpxy_ctx);
> +       if (ret) {
> +               dev_err(dev, "failed to verify RPMI attribute - err:%d\n", ret);
> +               goto fail_free_channel;
> +       }
> +
> +       /* Get number of performance domain */
> +       ret = rpmi_perf_get_num_domains(mpxy_ctx, &num_domains);
> +       if (ret) {
> +               dev_err(dev, "invalid number of perf domains - err:%d\n", ret);
> +               goto fail_free_channel;
> +       }

The domain space in RPMI performance for CPU and Device
is not separate and a domain can be either CPU or a Device.
How the driver will make sure that the domains which are returned
are CPU only and not the device.

> +MODULE_DEVICE_TABLE(of, rpmi_cpufreq_of_match);
> +
> +static struct platform_driver rpmi_cpufreq_platdrv = {
> +       .driver = {
> +               .name = "riscv-rpmi-performance",
> +               .of_match_table = rpmi_cpufreq_of_match,
> +       },
> +       .probe = rpmi_cpufreq_probe,
> +       .remove = rpmi_cpufreq_remove,
> +};
> +
> +module_platform_driver(rpmi_cpufreq_platdrv);
> +
> +MODULE_AUTHOR("Joshua Yeong <joshua.yeong@...rfivetech.com>");
> +MODULE_DESCRIPTION("CPUFreq Driver based on SBI MPXY extension");

NIT: CPUFreq driver based on SBI MPXY extension and RPMI protocol   -
something like this

> +MODULE_LICENSE("GPL");