Re: [Patch v6 2/2] ACPI: processor: reduce CPUFREQ thermal reduction pctg for Tegra241

[Sumit Gupta]

> > Current implementation of processor_thermal performs software throttling
> > in fixed steps of "20%" which can be too coarse for some platforms.
> > We observed some performance gain after reducing the throttle percentage.
> > Change the CPUFREQ thermal reduction percentage and maximum thermal steps
> > to be configurable. Also, update the default values of both for Nvidia
> > Tegra241 (Grace) SoC. The thermal reduction percentage is reduced to "5%"
> > and accordingly the maximum number of thermal steps are increased as they
> > are derived from the reduction percentage.
> >
> > Signed-off-by: Srikar Srimath Tirumala <srikars@xxxxxxxxxx>
> > Co-developed-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > ---
> >   drivers/acpi/arm64/Makefile          |  1 +
> >   drivers/acpi/arm64/thermal_cpufreq.c | 22 +++++++++++++
> >   drivers/acpi/internal.h              |  9 +++++
> >   drivers/acpi/processor_thermal.c     | 49 +++++++++++++++++++++++-----
> >   4 files changed, 72 insertions(+), 9 deletions(-)
> >   create mode 100644 drivers/acpi/arm64/thermal_cpufreq.c
> >
> > diff --git a/drivers/acpi/arm64/Makefile b/drivers/acpi/arm64/Makefile
> > index 143debc1ba4a..726944648c9b 100644
> > --- a/drivers/acpi/arm64/Makefile
> > +++ b/drivers/acpi/arm64/Makefile
> > @@ -5,3 +5,4 @@ obj-$(CONFIG_ACPI_GTDT)       += gtdt.o
> >   obj-$(CONFIG_ACPI_APMT)      += apmt.o
> >   obj-$(CONFIG_ARM_AMBA)               += amba.o
> >   obj-y                                += dma.o init.o
> > +obj-y                                += thermal_cpufreq.o
> > diff --git a/drivers/acpi/arm64/thermal_cpufreq.c b/drivers/acpi/arm64/thermal_cpufreq.c
> > new file mode 100644
> > index 000000000000..40d5806ed528
> > --- /dev/null
> > +++ b/drivers/acpi/arm64/thermal_cpufreq.c
> > @@ -0,0 +1,22 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +#include <linux/acpi.h>
> > +
> > +#include "../internal.h"
> > +
> > +#ifdef CONFIG_HAVE_ARM_SMCCC_DISCOVERY
> > +#define SMCCC_SOC_ID_T241      0x036b0241
>
> Sorry for missing this earlier. Not sure if the above define needs to be
> conditional. Even if it has to be, CONFIG_ARM_SMCCC_SOC_ID is more
> appropriate.

Will remove the ifdef.

> > +
> > +int acpi_arch_thermal_cpufreq_pctg(void)
> > +{
> > +     s32 soc_id = arm_smccc_get_soc_id_version();
> > +
> > +     /*
> > +      * Check JEP106 code for NVIDIA Tegra241 chip (036b:0241) and
> > +      * reduce the CPUFREQ Thermal reduction percentage to 5%.
> > +      */
> > +     if (soc_id == SMCCC_SOC_ID_T241)
> > +             return 5;
> > +
> > +     return 0;
> > +}
> > +#endif
> > diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
> > index 866c7c4ed233..ee213a8cddc5 100644
> > --- a/drivers/acpi/internal.h
> > +++ b/drivers/acpi/internal.h
> > @@ -85,6 +85,15 @@ bool acpi_scan_is_offline(struct acpi_device *adev, bool uevent);
> >   acpi_status acpi_sysfs_table_handler(u32 event, void *table, void *context);
> >   void acpi_scan_table_notify(void);
> >
> > +#ifdef CONFIG_HAVE_ARM_SMCCC_DISCOVERY
>
> It looks weird to add a such specific ARM config option in generic ACPI
> code/header.
>
> Does it make sense to add some new config this new feature you are adding
> or just use ARM64 and have CONFIG_HAVE_ARM_SMCCC_DISCOVERY check internally
> in the arch specific call.
>
> --
> Regards,
> Sudeep

Ok, will use CONFIG_ARM64 instead.
I think we don't need to check for CONFIG_HAVE_ARM_SMCCC_DISCOVERY 
inside the arch call as it returns zero if the soc_id value is different 
from Tegra241.

Best Regards,
Sumit Gupta