Re: [PATCH] LoongArch: Correct the calculation logic of thread_count

[Qiang Ma <maqianga@uniontech.com>]

在 2025/11/26 12:49, Huacai Chen 写道:
> Hi, Qiang,
>
> On Wed, Nov 26, 2025 at 10:37 AM Qiang Ma <maqianga@uniontech.com> wrote:
>> For thread_count, the current calculation method has a maximum of 255,
>> which may not be sufficient in the future. Therefore, we are correcting
>> it now.
> I think you should contact the Loongson BIOS team to confirm they will do so.

I contacted Li Chao from the Loongson BIOS team and had a brief 
communication.

bios will do this when it exceeds 256.

>
> And we can hardly meet the case that one socket contains more than 256
> cores (this is different from the case MAX_CPUS > 256)
According to Li Chao, the 256 logic core on a single chip should arrive 
in the next generation.
> Huacai
>
>> Reference: SMBIOS Specification, 7.5 Processor Information (Type 4)[1]
>>
>> [1]: https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.9.0.pdf
>>
>> Signed-off-by: Qiang Ma <maqianga@uniontech.com>
>> ---
>>   arch/loongarch/kernel/setup.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
>> index 25a87378e48e..760f5ce44384 100644
>> --- a/arch/loongarch/kernel/setup.c
>> +++ b/arch/loongarch/kernel/setup.c
>> @@ -56,6 +56,7 @@
>>   #define SMBIOS_FREQLOW_MASK            0xFF
>>   #define SMBIOS_CORE_PACKAGE_OFFSET     0x23
>>   #define SMBIOS_THREAD_PACKAGE_OFFSET   0x25
>> +#define SMBIOS_THREAD_PACKAGE_2_OFFSET 0x2E
>>   #define LOONGSON_EFI_ENABLE            (1 << 3)
>>
>>   unsigned long fw_arg0, fw_arg1, fw_arg2;
>> @@ -120,13 +121,19 @@ static void __init parse_cpu_table(const struct dmi_header *dm)
>>   {
>>          long freq_temp = 0;
>>          char *dmi_data = (char *)dm;
>> +       u8 thread_count;
>> +       u16 thread_count2;
>>
>>          freq_temp = ((*(dmi_data + SMBIOS_FREQHIGH_OFFSET) << 8) +
>>                          ((*(dmi_data + SMBIOS_FREQLOW_OFFSET)) & SMBIOS_FREQLOW_MASK));
>>          cpu_clock_freq = freq_temp * 1000000;
>>
>>          loongson_sysconf.cpuname = (void *)dmi_string_parse(dm, dmi_data[16]);
>> -       loongson_sysconf.cores_per_package = *(dmi_data + SMBIOS_THREAD_PACKAGE_OFFSET);
>> +       thread_count = *(dmi_data + SMBIOS_THREAD_PACKAGE_OFFSET);
>> +       thread_count2 = *(u16 *)(dmi_data + SMBIOS_THREAD_PACKAGE_2_OFFSET);
>> +       if (thread_count != 0)
>> +               loongson_sysconf.cores_per_package = dm->length >= 0x30 && thread_count == 0xFF ?
>> +                                                    thread_count2 : thread_count;
>>
>>          pr_info("CpuClock = %llu\n", cpu_clock_freq);
>>   }
>> --
>> 2.20.1
>>