[PATCH v3 5/5] powernv:cpufreq: Implement the driver->get() method

["Gautham R. Shenoy" <ego@linux.vnet.ibm.com>]

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

The current frequency of a cpu is reported through the sysfs file
cpuinfo_cur_freq. This requires the driver to implement a
"->get(unsigned int cpu)" method which will return the current
operating frequency.

Implement a function named powernv_cpufreq_get() which reads the local
pstate from the PMSR and returns the corresponding frequency.

Set the powernv_cpufreq_driver.get hook to powernv_cpufreq_get().

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
 drivers/cpufreq/powernv-cpufreq.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 46bee8a..ef6ed8c 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -206,6 +206,43 @@ static inline void set_pmspr(unsigned long sprn, unsigned long val)
 	BUG();
 }
 
+/*
+ * Computes the current frequency on this cpu
+ * and stores the result in *ret_freq.
+ */
+static void powernv_read_cpu_freq(void *ret_freq)
+{
+	unsigned long pmspr_val;
+	s8 local_pstate_id;
+	int *cur_freq, freq, pstate_id;
+
+	cur_freq = (int *)ret_freq;
+	pmspr_val = get_pmspr(SPRN_PMSR);
+
+	/* The local pstate id corresponds bits 48..55 in the PMSR.
+         * Note: Watch out for the sign! */
+	local_pstate_id = (pmspr_val >> 48) & 0xFF;
+	pstate_id = local_pstate_id;
+
+	freq = pstate_id_to_freq(pstate_id);
+	pr_debug("cpu %d pmsr %lx pstate_id %d frequency %d \n",
+		smp_processor_id(), pmspr_val, pstate_id, freq);
+	*cur_freq = freq;
+}
+
+/*
+ * Returns the cpu frequency as reported by the firmware for 'cpu'.
+ * This value is reported through the sysfs file cpuinfo_cur_freq.
+ */
+unsigned int powernv_cpufreq_get(unsigned int cpu)
+{
+	int ret_freq;
+
+	smp_call_function_any(cpu_sibling_mask(cpu), powernv_read_cpu_freq,
+			&ret_freq, 1);
+	return ret_freq;
+}
+
 static void set_pstate(void *pstate)
 {
 	unsigned long val;
@@ -297,6 +334,7 @@ static int powernv_cpufreq_target(struct cpufreq_policy *policy,
 static struct cpufreq_driver powernv_cpufreq_driver = {
 	.verify		= powernv_cpufreq_verify,
 	.target		= powernv_cpufreq_target,
+	.get		= powernv_cpufreq_get,
 	.init		= powernv_cpufreq_cpu_init,
 	.exit		= powernv_cpufreq_cpu_exit,
 	.name		= "powernv-cpufreq",
-- 
1.8.3.1