On 01/20/2015 11:15 AM, Michael Ellerman wrote:
> On Mon, 2015-19-01 at 11:32:51 UTC, Preeti U Murthy wrote:
>> The device tree now exposes the residency values for different idle states. 
>> Read
>> these values instead of calculating residency from the latency values. The 
>> values
>> exposed in the DT are validated for optimal power efficiency. However to 
>> maintain
>> compatibility with the older firmware code which does not expose residency
>> values, use default values as a fallback mechanism. While at it, clump
>> the common parts of device tree parsing into one chunk.
>>
>> Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com>
>> ---
>>
>>  drivers/cpuidle/cpuidle-powernv.c |   39 
>> ++++++++++++++++++++++++-------------
>>  1 file changed, 25 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/cpuidle/cpuidle-powernv.c 
>> b/drivers/cpuidle/cpuidle-powernv.c
>> index 2726663..9e732e1 100644
>> --- a/drivers/cpuidle/cpuidle-powernv.c
>> +++ b/drivers/cpuidle/cpuidle-powernv.c
>> @@ -162,7 +162,8 @@ static int powernv_add_idle_states(void)
>>      int dt_idle_states;
>>      const __be32 *idle_state_flags;
>>      const __be32 *idle_state_latency;
>> -    u32 len_flags, flags, latency_ns;
>> +    const __be32 *idle_state_residency;
>> +    u32 len_flags, flags, latency_ns, residency_ns;
>>      int i;
>>  
>>      /* Currently we have snooze statically defined */
>> @@ -186,14 +187,21 @@ static int powernv_add_idle_states(void)
>>              return nr_idle_states;
>>      }
>>  
>> +    idle_state_residency = of_get_property(power_mgt,
>> +                    "ibm,cpu-idle-state-residency-ns", NULL);
>> +    if (!idle_state_residency) {
>> +            pr_warn("DT-PowerMgmt: missing 
>> ibm,cpu-idle-state-residency-ns\n");
>> +            pr_warn("Falling back to default values\n");
>> +    }
> 
> This would be better done with something like:
> 
>       rc = of_read_property_u32(power_mgt, "ibm,cpu-idle-state-residency-ns", 
> &residency_ns);
>       if (!rc) {
>               pr_info("cpuidle-powernv: missing 
> ibm,cpu-idle-state-residency-ns\n");
>               residency_ns = 300000;
>       }

This looks like a better API, but the default residency values are different
for each idle state. So perhaps a patch like the below ?

--------------------------Start Patch------------------------------------------

From: Preeti U Murthy <pre...@linux.vnet.ibm.com>


---
 drivers/cpuidle/cpuidle-powernv.c |   54 +++++++++++++++++++++++--------------
 1 file changed, 33 insertions(+), 21 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c 
b/drivers/cpuidle/cpuidle-powernv.c
index aedec09..2031560 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -13,6 +13,7 @@
 #include <linux/notifier.h>
 #include <linux/clockchips.h>
 #include <linux/of.h>
+#include <linux/slab.h>
 
 #include <asm/machdep.h>
 #include <asm/firmware.h>
@@ -159,9 +160,9 @@ static int powernv_add_idle_states(void)
        int nr_idle_states = 1; /* Snooze */
        int dt_idle_states;
        const __be32 *idle_state_flags;
-       const __be32 *idle_state_latency;
-       u32 len_flags, flags, latency_ns;
-       int i;
+       u32 len_flags, flags;
+       u32 *latency_ns, *residency_ns;
+       int i, rc;
 
        /* Currently we have snooze statically defined */
 
@@ -177,34 +178,39 @@ static int powernv_add_idle_states(void)
                return nr_idle_states;
        }
 
-       idle_state_latency = of_get_property(power_mgt,
-                       "ibm,cpu-idle-state-latencies-ns", NULL);
-       if (!idle_state_latency) {
+       dt_idle_states = len_flags / sizeof(u32);
+
+       latency_ns = kzalloc(sizeof(*latency_ns) * dt_idle_states, GFP_KERNEL);
+       rc = of_property_read_u32(power_mgt,
+                       "ibm,cpu-idle-state-latencies-ns", latency_ns);
+       if (rc) {
                pr_warn("DT-PowerMgmt: missing 
ibm,cpu-idle-state-latencies-ns\n");
                return nr_idle_states;
        }
 
-       dt_idle_states = len_flags / sizeof(u32);
+       residency_ns = kzalloc(sizeof(*residency_ns) * dt_idle_states, 
GFP_KERNEL);
+       rc = of_property_read_u32(power_mgt,
+                       "ibm,cpu-idle-state-residency-ns", residency_ns);
+       if (rc) {
+               pr_warn("DT-PowerMgmt: missing 
ibm,cpu-idle-state-residency-ns\n");
+               pr_warn("Falling back to default values\n");
+       }
+
 
        for (i = 0; i < dt_idle_states; i++) {
 
                flags = be32_to_cpu(idle_state_flags[i]);
-
-               /* Cpuidle accepts exit_latency in us and we estimate
-                * target residency to be 10x exit_latency
+               /*
+                * Cpuidle accepts exit_latency and target_residency in us.
+                * Use default target_residency values if f/w does not expose 
it.
                 */
-               latency_ns = be32_to_cpu(idle_state_latency[i]);
                if (flags & OPAL_PM_NAP_ENABLED) {
                        /* Add NAP state */
                        strcpy(powernv_states[nr_idle_states].name, "Nap");
                        strcpy(powernv_states[nr_idle_states].desc, "Nap");
                        powernv_states[nr_idle_states].flags = 0;
-                       powernv_states[nr_idle_states].exit_latency =
-                                       ((unsigned int)latency_ns) / 1000;
-                       powernv_states[nr_idle_states].target_residency =
-                                       ((unsigned int)latency_ns / 100);
+                       powernv_states[nr_idle_states].target_residency = 100;
                        powernv_states[nr_idle_states].enter = &nap_loop;
-                       nr_idle_states++;
                }
 
                if (flags & OPAL_PM_SLEEP_ENABLED ||
@@ -213,13 +219,19 @@ static int powernv_add_idle_states(void)
                        strcpy(powernv_states[nr_idle_states].name, 
"FastSleep");
                        strcpy(powernv_states[nr_idle_states].desc, 
"FastSleep");
                        powernv_states[nr_idle_states].flags = 
CPUIDLE_FLAG_TIMER_STOP;
-                       powernv_states[nr_idle_states].exit_latency =
-                                       ((unsigned int)latency_ns) / 1000;
-                       powernv_states[nr_idle_states].target_residency =
-                                       ((unsigned int)latency_ns / 100);
+                       powernv_states[nr_idle_states].target_residency = 
300000;
                        powernv_states[nr_idle_states].enter = &fastsleep_loop;
-                       nr_idle_states++;
                }
+
+               powernv_states[nr_idle_states].exit_latency =
+                               ((unsigned int)latency_ns[i]) / 1000;
+
+               if (!rc) {
+                       powernv_states[nr_idle_states].target_residency =
+                               ((unsigned int)residency_ns[i]) / 1000;
+               }
+
+               nr_idle_states++;
        }
 
        return nr_idle_states;

Regards
Preeti U Murthy

> 
> cheers
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> Linuxppc-dev mailing list
> linuxppc-...@lists.ozlabs.org
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