Re: cpuidle/powernv: Read target_residency value of idle states from DT if available
From: Preeti U Murthy
Date: Tue Jan 20 2015 - 06:27:12 EST
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 <preeti@xxxxxxxxxxxxxxxxxx>
>> ---
>>
>> 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 <preeti@xxxxxxxxxxxxxxxxxx>
---
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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