Re: [PATCH -next] cpufreq: add stub for get_cpu_idle_time() to fix scsi/lpfc driver build

From: Randy Dunlap <rdunlap@infradead.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Linux PM list <linux-pm@vger.kernel.org>,
	linux-scsi <linux-scsi@vger.kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	James Smart <james.smart@broadcom.com>,
	Dick Kennedy <dick.kennedy@broadcom.com>
Subject: Re: [PATCH -next] cpufreq: add stub for get_cpu_idle_time() to fix scsi/lpfc driver build
Date: Tue, 7 Jul 2020 11:18:30 -0700	[thread overview]
Message-ID: <b35ed758-a964-2f76-d2d3-99c260458878@infradead.org> (raw)
In-Reply-To: <20200707030943.xkocccy6qy2c3hrx@vireshk-i7>

On 7/6/20 8:09 PM, Viresh Kumar wrote:
> On 06-07-20, 09:44, Randy Dunlap wrote:
>> From: Randy Dunlap <rdunlap@infradead.org>
>>
>> To fix a build error in drivers/scsi/lpfc/lpfc_sli.c when
>> CONFIG_CPU_FREQ is not set/enabled, add a stub function for
>> get_cpu_idle_time() in <linux/cpufreq.h>.
>>
>> ../drivers/scsi/lpfc/lpfc_sli.c: In function ‘lpfc_init_idle_stat_hb’:
>> ../drivers/scsi/lpfc/lpfc_sli.c:7330:26: error: implicit declaration of function ‘get_cpu_idle_time’; did you mean ‘set_cpu_active’? [-Werror=implicit-function-declaration]
> 
> And why is lpfc_sli.c using a cpufreq (supposedly internal, i.e. for
> cpufreq related parts) routine ? I think if you really need this, then
> it should be moved to a better common place and let everyone use it.

Viresh:

James Smart replied in another email thread with lpfc explanation for using
get_cpu_idle_time().  Please see
https://lore.kernel.org/linux-scsi/7ae1c7e3-ce8d-836b-1ae7-d4d00bd8f95c@broadcom.com/T/#md083717b1ff3a428c3b419dcc6d11cd03fee44c7

for this text:
""The driver is using cpu utilization in order to choose between softirq or work queues in handling an interrupt. Less-utilized, softirq is used. higher utilized, work queue is used.  The utilization is checked periodically via a heartbeat. ""

> I also see that drivers/macintosh/rack-meter.c has its own
> implementation for this.
> 
>>    idle_stat->prev_idle = get_cpu_idle_time(i, &wall, 1);
>>
>> Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
>> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>> Cc: Viresh Kumar <viresh.kumar@linaro.org>
>> Cc: linux-pm@vger.kernel.org
>> Cc: James Smart <james.smart@broadcom.com>
>> Cc: Dick Kennedy <dick.kennedy@broadcom.com>
>> Cc: linux-scsi@vger.kernel.org
>> ---
>>  include/linux/cpufreq.h |    4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> --- linux-next-20200706.orig/include/linux/cpufreq.h
>> +++ linux-next-20200706/include/linux/cpufreq.h
>> @@ -237,6 +237,10 @@ static inline unsigned int cpufreq_get_h
>>  {
>>  	return 0;
>>  }
>> +static inline u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy)
>> +{
>> +	return 0;
>> +}
>>  static inline void disable_cpufreq(void) { }
>>  #endif
>>  
> 

-- 
~Randy