Commit 0a4b4327 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/64s: Implement PMU override command line option 



It can be useful in simulators (with very constrained environments)
to allow some PMCs to run from boot so they can be sampled directly
by a test harness, rather than having to run perf.

A previous change freezes counters at boot by default, so provide
a boot time option to un-freeze (plus a bit more flexibility).

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Reviewed-by: default avatarAthira Jajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-13-npiggin@gmail.com
parent 245ebf8e

Documentation/admin-guide/kernel-parameters.txt

+8 −0
Original line number Diff line number Diff line
@@ -4144,6 +4144,14 @@ 
			Override pmtimer IOPort with a hex value.

			e.g. pmtmr=0x508



	pmu_override=	[PPC] Override the PMU.

			This option takes over the PMU facility, so it is no

			longer usable by perf. Setting this option starts the

			PMU counters by setting MMCR0 to 0 (the FC bit is

			cleared). If a number is given, then MMCR1 is set to

			that number, otherwise (e.g., 'pmu_override=on'), MMCR1

			remains 0.



	pm_debug_messages	[SUSPEND,KNL]

			Enable suspend/resume debug messages during boot up.

arch/powerpc/perf/core-book3s.c

+35 −0
Original line number Diff line number Diff line
@@ -2419,8 +2419,24 @@ int register_power_pmu(struct power_pmu *pmu) 
}



#ifdef CONFIG_PPC64

static bool pmu_override = false;

static unsigned long pmu_override_val;

static void do_pmu_override(void *data)

{

	ppc_set_pmu_inuse(1);

	if (pmu_override_val)

		mtspr(SPRN_MMCR1, pmu_override_val);

	mtspr(SPRN_MMCR0, mfspr(SPRN_MMCR0) & ~MMCR0_FC);

}



static int __init init_ppc64_pmu(void)

{

	if (cpu_has_feature(CPU_FTR_HVMODE) && pmu_override) {

		pr_warn("disabling perf due to pmu_override= command line option.\n");

		on_each_cpu(do_pmu_override, NULL, 1);

		return 0;

	}



	/* run through all the pmu drivers one at a time */

	if (!init_power5_pmu())

		return 0;
@@ -2442,4 +2458,23 @@ static int __init init_ppc64_pmu(void) 
		return init_generic_compat_pmu();

}

early_initcall(init_ppc64_pmu);



static int __init pmu_setup(char *str)

{

	unsigned long val;



	if (!early_cpu_has_feature(CPU_FTR_HVMODE))

		return 0;



	pmu_override = true;



	if (kstrtoul(str, 0, &val))

		val = 0;



	pmu_override_val = val;



	return 1;

}

__setup("pmu_override=", pmu_setup);



#endif