linux-kernel - Re: [PATCH 2/3] MIPS: Loongson: Add hwmon support for generic CPU

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Date:   Sat, 9 May 2020 10:23:47 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     WANG Xuerui <kernel@...0n.name>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Huacai Chen <chenhc@...ote.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH 2/3] MIPS: Loongson: Add hwmon support for generic CPU

On 05/08/2020 08:51 PM, WANG Xuerui wrote:
> On 2020/5/8 19:55, Tiezhu Yang wrote:
>
>> Add PRID_IMP_LOONGSON_64G case to enable hwmon support for Loongson
>> generic CPU such as 3A4000 and newer CPU.
>>
>> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
>> ---
>>   drivers/platform/mips/cpu_hwmon.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/platform/mips/cpu_hwmon.c 
>> b/drivers/platform/mips/cpu_hwmon.c
>> index add5f52..7b4bde1 100644
>> --- a/drivers/platform/mips/cpu_hwmon.c
>> +++ b/drivers/platform/mips/cpu_hwmon.c
>> @@ -43,6 +43,7 @@ int loongson3_cpu_temp(int cpu)
>>           break;
>>       case PRID_REV_LOONGSON3A_R3_0:
>>       case PRID_REV_LOONGSON3A_R3_1:
>> +    case PRID_IMP_LOONGSON_64G:
>>       default:
>>           reg = (reg & 0xffff)*731/0x4000 - 273;
>>           break;
>
> Hi,
>
> This is obviously wrong, as the value being matched is a PRID_REV. You 
> can tell from the neighboring match arms.
>
> Also, the LOONGSON_64G cores are 3A4000 and newer, that have CSR 
> support. The csr_temp_enable flag is probed in loongson_hwmon_init, 
> then the switch is simply never entered for these.

Hi Xuerui,

Thanks for your review. You are right.

I notice that this feature has been done in the commit 7507445b1993
("MIPS: Loongson: Add Loongson-3A R4 basic support"). My initial aim
is to get CPU temperature for the Loongson generic CPU when the flag
csr_temp_enable is false, but this is just the default case. So this
patch is meaningless, please ignore it.

Because patch 3/3 depends on this patch 2/3, I will remake and send v2
patch series without this patch.

Thanks,
Tiezhu Yang