On 2019/2/15 7:15, Rafael J. Wysocki wrote:
> On Thursday, February 14, 2019 2:58:21 PM CET Xiongfeng Wang wrote:
>>
>> On 2019/2/14 18:58, Rafael J. Wysocki wrote:
>>> On Thu, Feb 14, 2019 at 8:46 AM Xiongfeng Wang
>>> <wangxiongfeng2@xxxxxxxxxx> wrote:
>>>>
>>>> Hisilicon chips do not support delivered performance counter register
>>>> and reference performance counter register. But the platform can
>>>> calculate the real performance using its own method. This patch provide
>>>> a workaround for this problem, and other platforms can also use this
>>>> workaround framework. We reuse the desired performance register to
>>>> store the real performance calculated by the platform. After the
>>>> platform finished the frequency adjust, it gets the real performance and
>>>> writes it into desired performance register. OS can use it to calculate
>>>> the real frequency.
>>>>
>>>> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
>>>> ---
>>>> drivers/cpufreq/cppc_cpufreq.c | 70 ++++++++++++++++++++++++++++++++++++++++++
>>>> 1 file changed, 70 insertions(+)
>>>>
>>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>>>> index fd25c21c..da96fec 100644
>>>> --- a/drivers/cpufreq/cppc_cpufreq.c
>>>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>>>> @@ -33,6 +33,16 @@
>>>> /* Offest in the DMI processor structure for the max frequency */
>>>> #define DMI_PROCESSOR_MAX_SPEED 0x14
>>>>
>>>> +struct cppc_workaround_info {
>>>> + char oem_id[ACPI_OEM_ID_SIZE +1];
>>>> + char oem_table_id[ACPI_OEM_TABLE_ID_SIZE + 1];
>>>> + u32 oem_revision;
>>>> + unsigned int (*get_rate)(unsigned int cpu);
>>>> +};
>>>> +
>>>> +/* CPPC workaround for get_rate callback */
>>>> +unsigned int (*cppc_wa_get_rate)(unsigned int cpu);
>>>> +
>>>
>>> First off, please don't split the workaround material into two parts.
>>> IOW, the other new function added below can go here just fine IMO.
>>>
>>>> /*
>>>> * These structs contain information parsed from per CPU
>>>> * ACPI _CPC structures.
>>>> @@ -334,6 +344,9 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpunum)
>>>> struct cppc_cpudata *cpu = all_cpu_data[cpunum];
>>>> int ret;
>>>>
>>>> + if (cppc_wa_get_rate)
>>>> + return cppc_wa_get_rate(cpunum);
>>>
>>> Second, what is the value of using the function pointer above?
>>>
>>> All we need for now is a flag to indicate whether or not to call
>>> hisi_cppc_cpufreq_get_rate() here and return its return value.
>>
>> How about adding a pointer of 'struct cppc_workaround_info' to indicate whether we have
>> found a matches workaround ?
>> If I use a flag, I will need another variable to indicate which item of the workaround array 'wa_info'
>> to use.
>
> And why do you need to distinguish one of them from the other?
>
I was thinking about future extension. Different platform may have different implementation
of 'get_rate' in the future.
>
> .
>
