[PATCH 6/6] PM / devfreq: Set the min_freq and max_freq of devfreq device

[PATCH 6/6] PM / devfreq: Set the min_freq and max_freq of devfreq device

[Chanwoo Choi]

After probing the devfreq device driver, the value of both min_freq and
max_freq are zero(0). So, this patch initializes the 'min_freq' and 'max_freq'
field of devfreq device by using the freq_table array.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
---
 drivers/devfreq/devfreq.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index c292ceb7ff19..0b24ae7b7a48 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -121,6 +121,11 @@ static void devfreq_set_freq_table(struct devfreq *devfreq)
 		profile->freq_table[i] = freq;
 	}
 	rcu_read_unlock();
+
+	mutex_lock(&devfreq->lock);
+	devfreq->min_freq = profile->freq_table[0];
+	devfreq->max_freq = profile->freq_table[profile->max_state - 1];
+	mutex_unlock(&devfreq->lock);
 }
 
 /**
-- 
1.9.1

Re: [PATCH 6/6] PM / devfreq: Set the min_freq and max_freq of devfreq device

[MyungJoo Ham]

> After probing the devfreq device driver, the value of both min_freq and
> max_freq are zero(0). So, this patch initializes the 'min_freq' and 'max_freq'
> field of devfreq device by using the freq_table array.
> 
> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
> ---
>  drivers/devfreq/devfreq.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index c292ceb7ff19..0b24ae7b7a48 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -121,6 +121,11 @@ static void devfreq_set_freq_table(struct devfreq *devfreq)
>  		profile->freq_table[i] = freq;
>  	}
>  	rcu_read_unlock();
> +
> +	mutex_lock(&devfreq->lock);
> +	devfreq->min_freq = profile->freq_table[0];
> +	devfreq->max_freq = profile->freq_table[profile->max_state - 1];
> +	mutex_unlock(&devfreq->lock);
>  }

No, you should not do this.

It is allowed to use devfreq without both OPP and freq_table
assuming that the devfreq device may operate with very many
frequencies so that practically, we can virtually give it
any frequency numbers in a given range.
(cases where profile->max_state is 0 and it is not an error)

The value 0 is used for min/max_freq to declare
that min/max_freq is deactivated. Therefore, it is not
required to do so; they are not intended to show the hardware
configuration as well.

Cheers,
MyungJoo

Re: [PATCH 6/6] PM / devfreq: Set the min_freq and max_freq of devfreq device

[Chanwoo Choi]

On 2015년 11월 19일 19:10, MyungJoo Ham wrote:
>> After probing the devfreq device driver, the value of both min_freq and
>> max_freq are zero(0). So, this patch initializes the 'min_freq' and 'max_freq'
>> field of devfreq device by using the freq_table array.
>>
>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>> ---
>>  drivers/devfreq/devfreq.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index c292ceb7ff19..0b24ae7b7a48 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -121,6 +121,11 @@ static void devfreq_set_freq_table(struct devfreq *devfreq)
>>  		profile->freq_table[i] = freq;
>>  	}
>>  	rcu_read_unlock();
>> +
>> +	mutex_lock(&devfreq->lock);
>> +	devfreq->min_freq = profile->freq_table[0];
>> +	devfreq->max_freq = profile->freq_table[profile->max_state - 1];
>> +	mutex_unlock(&devfreq->lock);
>>  }
> 
> No, you should not do this.
> 
> It is allowed to use devfreq without both OPP and freq_table
> assuming that the devfreq device may operate with very many
> frequencies so that practically, we can virtually give it
> any frequency numbers in a given range.
> (cases where profile->max_state is 0 and it is not an error)
> 
> The value 0 is used for min/max_freq to declare
> that min/max_freq is deactivated. Therefore, it is not
> required to do so; they are not intended to show the hardware
> configuration as well.

This case consider the devfreq device using OPP because devfreq_set_freq_table()
get the number of OPP entry in OPP list before setting the min_freq/max_freq.
If the devfreq device don't use the OPP entry, devfreq_set_freq_table()
will return without any operation.

IMHO, when devfreq device uses the OPP table including the frequency,
min_freq/max_freq should show the correct value as CPUFREQ framework.

Regards,
Chanwoo CHoi