Re: [PATCH v6 8/8] ACPI: CPPC: Add three functions related to autonomous selection

["zhenglifeng (A)" <zhenglifeng1@huawei.com>]

On 2025/4/10 2:59, Mario Limonciello wrote:
> On 4/9/2025 1:57 AM, Lifeng Zheng wrote:
>> cppc_set_epp - write energy performance preference register value, based on
>> ACPI 6.5, s8.4.6.1.7
>>
>> cppc_get_auto_act_window - read autonomous activity window register value,
>> based on ACPI 6.5, s8.4.6.1.6
>>
>> cppc_set_auto_act_window - write autonomous activity window register value,
>> based on ACPI 6.5, s8.4.6.1.6
>>
>> Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
>> Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
>> ---
>>   drivers/acpi/cppc_acpi.c | 80 ++++++++++++++++++++++++++++++++++++++++
>>   include/acpi/cppc_acpi.h | 24 ++++++++++++
>>   2 files changed, 104 insertions(+)
>>
>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
>> index ef2394c074e3..3d5eace44af5 100644
>> --- a/drivers/acpi/cppc_acpi.c
>> +++ b/drivers/acpi/cppc_acpi.c
>> @@ -1608,6 +1608,86 @@ int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable)
>>   }
>>   EXPORT_SYMBOL_GPL(cppc_set_epp_perf);
>>   +/**
>> + * cppc_set_epp() - Write the EPP register.
>> + * @cpu: CPU on which to write register.
>> + * @epp_val: Value to write to the EPP register.
>> + */
>> +int cppc_set_epp(int cpu, u64 epp_val)
> 
> Any reason this is a u64 argument when the biggest value you can support is 0xFF?  Presumably you could drop the the bounds check below if you limited the variable size.

cppc_get_epp_perf() uses u64, so I think it is better to keep the same.

> 
>> +{
>> +    if (epp_val > CPPC_ENERGY_PERF_MAX)
>> +        return -EINVAL;
>> +
>> +    return cppc_set_reg_val(cpu, ENERGY_PERF, epp_val);
>> +}
>> +EXPORT_SYMBOL_GPL(cppc_set_epp);
>> +
>> +/**
>> + * cppc_get_auto_act_window() - Read autonomous activity window register.
>> + * @cpu: CPU from which to read register.
>> + * @auto_act_window: Return address.
>> + *
>> + * According to ACPI 6.5, s8.4.6.1.6, the value read from the autonomous
>> + * activity window register consists of two parts: a 7 bits value indicate
>> + * significand and a 3 bits value indicate exponent.
>> + */
>> +int cppc_get_auto_act_window(int cpu, u64 *auto_act_window)
>> +{
>> +    unsigned int exp;
>> +    u64 val, sig;
>> +    int ret;
>> +
>> +    ret = cppc_get_reg_val(cpu, AUTO_ACT_WINDOW, &val);
>> +    if (ret)
>> +        return ret;
>> +
>> +    sig = val & CPPC_AUTO_ACT_WINDOW_MAX_SIG;
>> +    exp = (val >> CPPC_AUTO_ACT_WINDOW_SIG_BIT_SIZE) & CPPC_AUTO_ACT_WINDOW_MAX_EXP;
>> +    *auto_act_window = sig * int_pow(10, exp);
>> +
>> +    return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(cppc_get_auto_act_window);
> 
> Since this is exported code, do you perhaps want a check that auto_act_window is not NULL to avoid a possible accidental NULL pointer dereference?

Yes. Make sense. Thanks!

> 
>> +
>> +/**
>> + * cppc_set_auto_act_window() - Write autonomous activity window register.
>> + * @cpu: CPU on which to write register.
>> + * @auto_act_window: usec value to write to the autonomous activity window register.
>> + *
>> + * According to ACPI 6.5, s8.4.6.1.6, the value to write to the autonomous
>> + * activity window register consists of two parts: a 7 bits value indicate
>> + * significand and a 3 bits value indicate exponent.
>> + */
>> +int cppc_set_auto_act_window(int cpu, u64 auto_act_window)
>> +{
>> +    /* The max value to stroe is 1270000000 */
> 
> store

Thanks!

> 
>> +    u64 max_val = CPPC_AUTO_ACT_WINDOW_MAX_SIG * int_pow(10, CPPC_AUTO_ACT_WINDOW_MAX_EXP);
>> +    int exp = 0;
>> +    u64 val;
>> +
>> +    if (auto_act_window > max_val)
>> +        return -EINVAL;
>> +
>> +    /*
>> +     * The max significand is 127, when auto_act_window is larger than
>> +     * 129, discard the precision of the last digit and increase the
>> +     * exponent by 1.
>> +     */
>> +    while (auto_act_window > CPPC_AUTO_ACT_WINDOW_SIG_CARRY_THRESH) {
>> +        auto_act_window /= 10;
>> +        exp += 1;
>> +    }
>> +
>> +    /* For 128 and 129, cut it to 127. */
>> +    if (auto_act_window > CPPC_AUTO_ACT_WINDOW_MAX_SIG)
>> +        auto_act_window = CPPC_AUTO_ACT_WINDOW_MAX_SIG;
>> +
>> +    val = (exp << CPPC_AUTO_ACT_WINDOW_SIG_BIT_SIZE) + auto_act_window;
>> +
>> +    return cppc_set_reg_val(cpu, AUTO_ACT_WINDOW, val);
>> +}
>> +EXPORT_SYMBOL_GPL(cppc_set_auto_act_window);
>> +
>>   /**
>>    * cppc_get_auto_sel() - Read autonomous selection register.
>>    * @cpu: CPU from which to read register.
>> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
>> index 31767c65be20..325e9543e08f 100644
>> --- a/include/acpi/cppc_acpi.h
>> +++ b/include/acpi/cppc_acpi.h
>> @@ -32,6 +32,15 @@
>>   #define    CMD_READ 0
>>   #define    CMD_WRITE 1
>>   +#define CPPC_AUTO_ACT_WINDOW_SIG_BIT_SIZE    (7)
>> +#define CPPC_AUTO_ACT_WINDOW_EXP_BIT_SIZE    (3)
>> +#define CPPC_AUTO_ACT_WINDOW_MAX_SIG    ((1 << CPPC_AUTO_ACT_WINDOW_SIG_BIT_SIZE) - 1)
>> +#define CPPC_AUTO_ACT_WINDOW_MAX_EXP    ((1 << CPPC_AUTO_ACT_WINDOW_EXP_BIT_SIZE) - 1)
>> +/* CPPC_AUTO_ACT_WINDOW_MAX_SIG is 127, so 128 and 129 will decay to 127 when writing */
>> +#define CPPC_AUTO_ACT_WINDOW_SIG_CARRY_THRESH 129
>> +
>> +#define CPPC_ENERGY_PERF_MAX    (0xFF)
>> +
>>   /* Each register has the folowing format. */
>>   struct cpc_reg {
>>       u8 descriptor;
>> @@ -159,6 +168,9 @@ extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val);
>>   extern int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val);
>>   extern int cppc_get_epp_perf(int cpunum, u64 *epp_perf);
>>   extern int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable);
>> +extern int cppc_set_epp(int cpu, u64 epp_val);
>> +extern int cppc_get_auto_act_window(int cpu, u64 *auto_act_window);
>> +extern int cppc_set_auto_act_window(int cpu, u64 auto_act_window);
>>   extern int cppc_get_auto_sel(int cpu, bool *enable);
>>   extern int cppc_set_auto_sel(int cpu, bool enable);
>>   extern int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf);
>> @@ -229,6 +241,18 @@ static inline int cppc_get_epp_perf(int cpunum, u64 *epp_perf)
>>   {
>>       return -EOPNOTSUPP;
>>   }
>> +static inline int cppc_set_epp(int cpu, u64 epp_val)
>> +{
>> +    return -EOPNOTSUPP;
>> +}
>> +static inline int cppc_get_auto_act_window(int cpu, u64 *auto_act_window)
>> +{
>> +    return -EOPNOTSUPP;
>> +}
>> +static inline int cppc_set_auto_act_window(int cpu, u64 auto_act_window)
>> +{
>> +    return -EOPNOTSUPP;
>> +}
>>   static inline int cppc_get_auto_sel(int cpu, bool *enable)
>>   {
>>       return -EOPNOTSUPP;
>