linux-kernel - Re: [PATCH v2 1/6] acpi: cppc: Add min and max perf reg writing support

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Date:   Fri, 13 Jan 2023 12:01:01 +0530
From:   Wyes Karny <wyes.karny@....com>
To:     Mario Limonciello <mario.limonciello@....com>,
        Rafael J Wysocki <rafael@...nel.org>,
        Huang Rui <ray.huang@....com>,
        Jonathan Corbet <corbet@....net>,
        Viresh Kumar <viresh.kumar@...aro.org>, Perry.Yuan@....com,
        Ananth Narayan <ananth.narayan@....com>, gautham.shenoy@....com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Bagas Sanjaya <bagasdotme@...il.com>,
        santosh.shukla@....com
Subject: Re: [PATCH v2 1/6] acpi: cppc: Add min and max perf reg writing
 support

Hi Mario,

On 1/13/2023 11:07 AM, Mario Limonciello wrote:
> On 1/12/23 23:21, Wyes Karny wrote:
>> Currently writing of min and max perf register is deferred in
>> cppc_set_perf function. In CPPC guided mode, these registers needed to
>> be written to guide PMFW about min and max perf levels. Add this support
> 
> This is generic code, so  I think rather than PMFW you should just say "the platform".
> 
>> to make guided mode work properly on shared memory systems.
> 
> on AMD shared memory systems.
> 
>>
>> Signed-off-by: Wyes Karny <wyes.karny@....com>
> 
> With the commit message cleaned up:
> 
> Reviewed-by: Mario Limonciello <mario.limonciello@....com>

Will do the cleanup part. Thanks for reviewing!

>> ---
>>   drivers/acpi/cppc_acpi.c | 16 ++++++++--------
>>   1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
>> index 02d83c807271..c936ff503965 100644
>> --- a/drivers/acpi/cppc_acpi.c
>> +++ b/drivers/acpi/cppc_acpi.c
>> @@ -1487,7 +1487,7 @@ EXPORT_SYMBOL_GPL(cppc_set_enable);
>>   int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>>   {
>>       struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
>> -    struct cpc_register_resource *desired_reg;
>> +    struct cpc_register_resource *desired_reg, *min_perf_reg, *max_perf_reg;
>>       int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
>>       struct cppc_pcc_data *pcc_ss_data = NULL;
>>       int ret = 0;
>> @@ -1498,6 +1498,8 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>>       }
>>         desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
>> +    min_perf_reg = &cpc_desc->cpc_regs[MIN_PERF];
>> +    max_perf_reg = &cpc_desc->cpc_regs[MAX_PERF];
>>         /*
>>        * This is Phase-I where we want to write to CPC registers
>> @@ -1506,7 +1508,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>>        * Since read_lock can be acquired by multiple CPUs simultaneously we
>>        * achieve that goal here
>>        */
>> -    if (CPC_IN_PCC(desired_reg)) {
>> +    if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg)) {
>>           if (pcc_ss_id < 0) {
>>               pr_debug("Invalid pcc_ss_id\n");
>>               return -ENODEV;
>> @@ -1529,13 +1531,11 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>>           cpc_desc->write_cmd_status = 0;
>>       }
>>   -    /*
>> -     * Skip writing MIN/MAX until Linux knows how to come up with
>> -     * useful values.
>> -     */
>>       cpc_write(cpu, desired_reg, perf_ctrls->desired_perf);
>> +    cpc_write(cpu, min_perf_reg, perf_ctrls->min_perf);
>> +    cpc_write(cpu, max_perf_reg, perf_ctrls->max_perf);
>>   -    if (CPC_IN_PCC(desired_reg))
>> +    if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg))
>>           up_read(&pcc_ss_data->pcc_lock);    /* END Phase-I */
>>       /*
>>        * This is Phase-II where we transfer the ownership of PCC to Platform
>> @@ -1583,7 +1583,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>>        * case during a CMD_READ and if there are pending writes it delivers
>>        * the write command before servicing the read command
>>        */
>> -    if (CPC_IN_PCC(desired_reg)) {
>> +    if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg)) {
>>           if (down_write_trylock(&pcc_ss_data->pcc_lock)) {/* BEGIN Phase-II */
>>               /* Update only if there are pending write commands */
>>               if (pcc_ss_data->pending_pcc_write_cmd)
> 

-- 
Thanks & Regards,
Wyes