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Subject: RE: [PATCH] cpufreq: Add Kryo CPU scaling driver
Date:   Tue, 22 May 2018 10:59:07 +0300
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OK, I think I found out the way. Would this be correct?
-------------------------------------------------------------------------=
----------------------
extern struct cpu_topology cpu_topology[NR_CPUS];

static struct device *qcom_cpufreq_kryo_get_cluster_lead(int cluster)
{
	unsigned cpu;

	for_each_possible_cpu(cpu) {
		if ((cluster =3D=3D cpu_topology[cpu].cluster_id) &&
			(0 =3D=3D cpu_topology[cpu].core_id))
			return get_cpu_device(cpu);
	}

	return NULL;
}
-------------------------------------------------------------------------=
----------------------

> -----Original Message-----
> From: ilialin@codeaurora.org <ilialin@codeaurora.org>
> Sent: Tuesday, May 22, 2018 09:56
> To: 'Sudeep Holla' <sudeep.holla@arm.com>; 'mturquette@baylibre.com'
> <mturquette@baylibre.com>; 'sboyd@kernel.org' <sboyd@kernel.org>;
> 'robh@kernel.org' <robh@kernel.org>; 'mark.rutland@arm.com'
> <mark.rutland@arm.com>; 'viresh.kumar@linaro.org'
> <viresh.kumar@linaro.org>; 'nm@ti.com' <nm@ti.com>;
> 'lgirdwood@gmail.com' <lgirdwood@gmail.com>; 'broonie@kernel.org'
> <broonie@kernel.org>; 'andy.gross@linaro.org' <andy.gross@linaro.org>;
> 'david.brown@linaro.org' <david.brown@linaro.org>;
> 'catalin.marinas@arm.com' <catalin.marinas@arm.com>;
> 'will.deacon@arm.com' <will.deacon@arm.com>; 'rjw@rjwysocki.net'
> <rjw@rjwysocki.net>; 'linux-clk@vger.kernel.org' <linux-
> clk@vger.kernel.org>
> Cc: 'devicetree@vger.kernel.org' <devicetree@vger.kernel.org>; 'linux-
> kernel@vger.kernel.org' <linux-kernel@vger.kernel.org>; 'linux-
> pm@vger.kernel.org' <linux-pm@vger.kernel.org>; 'linux-arm-
> msm@vger.kernel.org' <linux-arm-msm@vger.kernel.org>; 'linux-
> soc@vger.kernel.org' <linux-soc@vger.kernel.org>; 'linux-arm-
> kernel@lists.infradead.org' <linux-arm-kernel@lists.infradead.org>;
> 'rnayak@codeaurora.org' <rnayak@codeaurora.org>;
> 'amit.kucheria@linaro.org' <amit.kucheria@linaro.org>;
> 'nicolas.dechesne@linaro.org' <nicolas.dechesne@linaro.org>;
> 'celster@codeaurora.org' <celster@codeaurora.org>;
> 'tfinkel@codeaurora.org' <tfinkel@codeaurora.org>
> Subject: RE: [PATCH] cpufreq: Add Kryo CPU scaling driver
>=20
>=20
>=20
> > -----Original Message-----
> > From: Sudeep Holla <sudeep.holla@arm.com>
> > Sent: Monday, May 21, 2018 16:05
> > To: ilialin@codeaurora.org; mturquette@baylibre.com; =
sboyd@kernel.org;
> > robh@kernel.org; mark.rutland@arm.com; viresh.kumar@linaro.org;
> > nm@ti.com; lgirdwood@gmail.com; broonie@kernel.org;
> > andy.gross@linaro.org; david.brown@linaro.org;
> > catalin.marinas@arm.com; will.deacon@arm.com; rjw@rjwysocki.net;
> > linux-clk@vger.kernel.org
> > Cc: Sudeep Holla <sudeep.holla@arm.com>; devicetree@vger.kernel.org;
> > linux-kernel@vger.kernel.org; linux-pm@vger.kernel.org; linux-arm-
> > msm@vger.kernel.org; linux-soc@vger.kernel.org; linux-arm-
> > kernel@lists.infradead.org; rnayak@codeaurora.org;
> > amit.kucheria@linaro.org; nicolas.dechesne@linaro.org;
> > celster@codeaurora.org; tfinkel@codeaurora.org
> > Subject: Re: [PATCH] cpufreq: Add Kryo CPU scaling driver
> >
> >
> >
> > On 21/05/18 13:57, ilialin@codeaurora.org wrote:
> > >
> > [...]
> >
> > >>> +#include <linux/cpu.h>
> > >>> +#include <linux/err.h>
> > >>> +#include <linux/init.h>
> > >>> +#include <linux/kernel.h>
> > >>> +#include <linux/module.h>
> > >>> +#include <linux/nvmem-consumer.h> #include <linux/of.h> =
#include
> > >>> +<linux/platform_device.h> #include <linux/pm_opp.h> #include
> > >>> +<linux/slab.h> #include <linux/soc/qcom/smem.h>
> > >>> +
> > >>> +#define MSM_ID_SMEM	137
> > >>> +#define SILVER_LEAD	0
> > >>> +#define GOLD_LEAD	2
> > >>> +
> > >>
> > >> So I gather form other emails, that these are physical cpu
> > >> number(not even unique identifier like MPIDR). Will this work on
> > >> parts or platforms that need to boot in GOLD LEAD cpus.
> > >
> > > The driver is for Kryo CPU, which (and AFAIK all multicore MSMs)
> > > always boots on the CPU0.
> >
> >
> > That may be true and I am not that bothered about it. But assuming
> > physical ordering from the logical cpu number is *incorrect* and =
will
> > break if kernel decides to change the allocation algorithm. Kernel
> > provides no guarantee on that, so you need to depend on some =
physical
> > ID or may be DT to achieve what your want. But the current code as =
it
> stands is wrong.
>=20
> Got your point. In fact CPUs are numbered 0-3 and ordered into 2 =
clusters in
> the DT:
>=20
> cpus {
> 	#address-cells =3D <2>;
> 	#size-cells =3D <0>;
>=20
> 	CPU0: cpu@0 {
> 		...
> 		reg =3D <0x0 0x0>;
> 		...
> 	};
>=20
> 	CPU1: cpu@1 {
> 		...
> 		reg =3D <0x0 0x1>;
> 		...
> 	};
>=20
> 	CPU2: cpu@100 {
> 		...
> 		reg =3D <0x0 0x100>;
> 		...
> 	};
>=20
> 	CPU3: cpu@101 {
> 		...
> 		reg =3D <0x0 0x101>;
> 		...
> 	};
>=20
> 	cpu-map {
> 		cluster0 {
> 			core0 {
> 				cpu =3D <&CPU0>;
> 			};
>=20
> 			core1 {
> 				cpu =3D <&CPU1>;
> 			};
> 		};
>=20
> 		cluster1 {
> 			core0 {
> 				cpu =3D <&CPU2>;
> 			};
>=20
> 			core1 {
> 				cpu =3D <&CPU3>;
> 			};
> 		};
> 	};
> };
>=20
> As far, as I understand, they are probed in the same order. However, =
to be
> certain that the physical CPU is the one I intend to configure, I have =
to fetch
> the device structure pointer for the cpu-map -> clusterX -> core0 -> =
cpu path.
> Could you suggest a kernel API to do that?
>=20
>=20
>=20
> >
> > --
> > Regards,
> > Sudeep