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

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Message-ID: <CABdD5x=T0pXWCSHL+An2Nwsaz-kbYnGga5vt0OfdCwm-o493Dw@mail.gmail.com>
Date: Tue, 13 Jan 2026 11:01:55 +0530
From: Rahul Pathak <rahul@...mations.net>
To: Joshua Yeong <joshua.yeong@...rfivetech.com>
Cc: "anup@...infault.org" <anup@...infault.org>, Leyfoon Tan <leyfoon.tan@...rfivetech.com>, 
	"robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>, 
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	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>, 
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	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-pm@...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

On Tue, Jan 13, 2026 at 8:05 AM Joshua Yeong
<joshua.yeong@...rfivetech.com> wrote:
>
> 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?
>
> >

Yes