[PATCH] cpufreq: acpi: Add comment under ACPI_ADR_SPACE_SYSTEM_IO case

[Viresh Kumar]

policy->cur is now set by cpufreq core when cpufreq_driver->get() is defined and
so drivers aren't required to set it. When space_id is ACPI_ADR_SPACE_SYSTEM_IO
for acpi cpufreq driver it doesn't set ->get to a valid function pointer and so
policy->cur is required to be set by driver.

This is already followed in acpi-cpufreq driver. This patch adds a comment
describing why we need to set policy->cur from driver.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
This change was requested by Rafael here:
http://www.spinics.net/lists/linux-acpi/msg46748.html

 drivers/cpufreq/acpi-cpufreq.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index a8dac7b..8ecd74e 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -838,6 +838,7 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	switch (perf->control_register.space_id) {
 	case ACPI_ADR_SPACE_SYSTEM_IO:
 		/* Current speed is unknown and not detectable by IO port */
+		/* ->cur wouldn't be set by core as ->get() is NULL */
 		policy->cur = acpi_cpufreq_guess_freq(data, policy->cpu);
 		break;
 	case ACPI_ADR_SPACE_FIXED_HARDWARE:
-- 
1.7.12.rc2.18.g61b472e

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