Subject: Re: [PATCH V4] cpuidle/powernv: Read target_residency value of idle states from DT if available

From: Preeti U Murthy <[email-masked]>
Date: Wed, 18 Feb 2015 10:13:23 +0530

On 02/17/2015 11:23 PM, Rafael J. Wysocki wrote:
> On Tuesday, February 17, 2015 01:29:10 PM Preeti U Murthy wrote:
>> Hi Rafael,
> 
> Hi,
> 
>> Can you please pull this patch ?
> 
> Sorry, I wasn't sure whether or not the patch was for me to take and then
> I've been traveling lately.  Applied now.

Hi Rafael,

I saw that the kbuild bot reported build issues around pr_warn() in this patch.
I have fixed this and below is the corrected patch. Do let me know if I have
to send it out as a separate version/RESEND tag.

> 
>> Another patch based on top of this is waiting to be pulled:
>> [PATCH] driver/cpuidle-powernv: Avoid endianness conversions while parsing DT
> 
> OK, have you posted it already?
Yes I have. https://lkml.org/lkml/2015/2/3/24. This patch is also waiting to
be pulled by you. There was some confusion around who should pull this, but
since it all the code is in the driver, we thought it would be best if you pulled it.

Thanks

--------------------------- PATCH -------------------------------------

[PATCH V4] cpuidle/powernv: Read target_residency value of idle states from DT if available

From: Preeti U Murthy <[email-masked]>

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, use better
APIs to parse the powermgmt device tree node.

Signed-off-by: Preeti U Murthy <[email-masked]>
Acked-by: Stewart Smith <[email-masked]>
Acked-by: Michael Ellerman <[email-masked]>
---
 drivers/cpuidle/cpuidle-powernv.c |   69 +++++++++++++++++++++----------------
 1 file changed, 40 insertions(+), 29 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index aedec09..30d4229 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>
@@ -159,69 +160,79 @@ 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 */
 
 	power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
 	if (!power_mgt) {
 		pr_warn("opal: PowerMgmt Node not found\n");
-		return nr_idle_states;
+		goto out;
 	}
 
-	idle_state_flags = of_get_property(power_mgt, "ibm,cpu-idle-state-flags", &len_flags);
+	idle_state_flags = of_get_property(power_mgt,
+				"ibm,cpu-idle-state-flags", &len_flags);
 	if (!idle_state_flags) {
-		pr_warn("DT-PowerMgmt: missing ibm,cpu-idle-state-flags\n");
-		return nr_idle_states;
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-flags in DT\n");
+		goto out;
 	}
 
-	idle_state_latency = of_get_property(power_mgt,
-			"ibm,cpu-idle-state-latencies-ns", NULL);
-	if (!idle_state_latency) {
-		pr_warn("DT-PowerMgmt: missing ibm,cpu-idle-state-latencies-ns\n");
-		return nr_idle_states;
+	dt_idle_states = len_flags / sizeof(u32);
+
+	latency_ns = kzalloc(sizeof(*latency_ns) * dt_idle_states, GFP_KERNEL);
+	rc = of_property_read_u32_array(power_mgt,
+		"ibm,cpu-idle-state-latencies-ns", latency_ns, dt_idle_states);
+	if (rc) {
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-latencies-ns in DT\n");
+		goto out_free_latency;
 	}
 
-	dt_idle_states = len_flags / sizeof(u32);
+	residency_ns = kzalloc(sizeof(*residency_ns) * dt_idle_states, GFP_KERNEL);
+	rc = of_property_read_u32_array(power_mgt,
+		"ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);
 
 	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 ||
+		} else if (flags & OPAL_PM_SLEEP_ENABLED ||
 			flags & OPAL_PM_SLEEP_ENABLED_ER1) {
 			/* Add FASTSLEEP state */
 			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++;
 	}
 
+	kfree(residency_ns);
+out_free_latency:
+	kfree(latency_ns);
+out:
 	return nr_idle_states;
 }

Regards
Preeti U Murthy