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

[Sudeep Holla <sudeep.holla@arm.com>]

On Fri, Nov 10, 2023 at 12:03:22AM +0530, Sumit Gupta wrote:
> From: Srikar Srimath Tirumala <srikars@nvidia.com>
> 
> 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@nvidia.com>
> Co-developed-by: Sumit Gupta <sumitg@nvidia.com>
> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
> ---
>  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.

> +
> +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

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