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

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Message-ID:
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Date: Tue, 13 Jan 2026 02:35:16 +0000
From: Joshua Yeong <joshua.yeong@...rfivetech.com>
To: Rahul Pathak <rahul@...mations.net>
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Subject: RE: [PATCH 4/5] cpufreq: Add cpufreq driver for the RISC-V RPMI
 performance service group

On Monday, January 12, 2026 6:47 PM, Rahul Pathak <rahul@...mations.net> wrote:

> > +
> > +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.

I think we need to enhance the RPMI spec to include information for types of device.
What do you think?

>
> > +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");