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Date:   Fri, 17 Nov 2023 16:08:02 +0530
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Subject: Re: [Patch v6 2/2] ACPI: processor: reduce CPUFREQ thermal reduction
 pctg for Tegra241
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To:     Sudeep Holla <sudeep.holla@arm.com>
CC:     <rafael@kernel.org>, <rui.zhang@intel.com>, <lenb@kernel.org>,
        <lpieralisi@kernel.org>, <guohanjun@huawei.com>,
        <linux-acpi@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>, <treding@nvidia.com>,
        <jonathanh@nvidia.com>, <bbasu@nvidia.com>, <sanjayc@nvidia.com>,
        <ksitaraman@nvidia.com>, <srikars@nvidia.com>,
        <jbrasen@nvidia.com>, Sumit Gupta <sumitg@nvidia.com>
References: <20231109183322.28039-1-sumitg@nvidia.com>
 <20231109183322.28039-3-sumitg@nvidia.com> <20231110101507.GB1505974@bogus>
From:   Sumit Gupta <sumitg@nvidia.com>
In-Reply-To: <20231110101507.GB1505974@bogus>
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>> 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.
> 

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