Re: [PATCH v3 4/6] cpufreq: powernv: Call throttle_check() on receiving OCC_THROTTLE

On 05/05/2015 12:03 PM, Shilpasri G Bhat wrote:

Hi Preeti,

On 05/05/2015 09:30 AM, Preeti U Murthy wrote:

quoted

Hi Shilpa,

On 05/04/2015 02:24 PM, Shilpasri G Bhat wrote:

quoted

Re-evaluate the chip's throttled state on recieving OCC_THROTTLE
notification by executing *throttle_check() on any one of the cpu on
the chip. This is a sanity check to verify if we were indeed
throttled/unthrottled after receiving OCC_THROTTLE notification.

We cannot call *throttle_check() directly from the notification
handler because we could be handling chip1's notification in chip2. So
initiate an smp_call to execute *throttle_check(). We are irq-disabled
in the notification handler, so use a worker thread to smp_call
throttle_check() on any of the cpu in the chipmask.

I see that the first patch takes care of reporting *per-chip* throttling
for pmax capping condition. But where are we taking care of reporting
"pstate set to safe" and "freq control disabled" scenarios per-chip ?

IMO let us not have "psafe" and "freq control disabled" states managed per-chip.
Because when the above two conditions occur it is likely to happen across all
chips during an OCC reset cycle. So I am setting 'throttled' to false on
OCC_ACTIVE and re-verifying if it actually is the case by invoking
*throttle_check().

Alright like I pointed in the previous reply, a comment to indicate that
psafe and freq control disabled conditions will fail when occ is
inactive and that all chips face the consequence of this will help.

quoted

quoted

Signed-off-by: Shilpasri G Bhat <redacted>
---
 drivers/cpufreq/powernv-cpufreq.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 9268424..9618813 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -50,6 +50,8 @@ static bool rebooting, throttled, occ_reset;
 static struct chip {
 	unsigned int id;
 	bool throttled;
+	cpumask_t mask;
+	struct work_struct throttle;
 } *chips;

 static int nr_chips;

@@ -310,8 +312,9 @@ static inline unsigned int get_nominal_index(void)
 	return powernv_pstate_info.max - powernv_pstate_info.nominal;
 }

-static void powernv_cpufreq_throttle_check(unsigned int cpu)
+static void powernv_cpufreq_throttle_check(void *data)
 {
+	unsigned int cpu = smp_processor_id();
 	unsigned long pmsr;
 	int pmsr_pmax, pmsr_lp, i;

@@ -373,7 +376,7 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
 		return 0;

 	if (!throttled)
-		powernv_cpufreq_throttle_check(smp_processor_id());
+		powernv_cpufreq_throttle_check(NULL);

 	freq_data.pstate_id = powernv_freqs[new_index].driver_data;

@@ -418,6 +421,14 @@ static struct notifier_block powernv_cpufreq_reboot_nb = {
 	.notifier_call = powernv_cpufreq_reboot_notifier,
 };

+void powernv_cpufreq_work_fn(struct work_struct *work)
+{
+	struct chip *chip = container_of(work, struct chip, throttle);
+
+	smp_call_function_any(&chip->mask,
+			      powernv_cpufreq_throttle_check, NULL, 0);
+}
+
 static char throttle_reason[][30] = {
 					"No throttling",
 					"Power Cap",

@@ -433,6 +444,7 @@ static int powernv_cpufreq_occ_msg(struct notifier_block *nb,
 	struct opal_msg *occ_msg = msg;
 	uint64_t token;
 	uint64_t chip_id, reason;
+	int i;

 	if (msg_type != OPAL_MSG_OCC)
 		return 0;

@@ -466,6 +478,10 @@ static int powernv_cpufreq_occ_msg(struct notifier_block *nb,
 			occ_reset = false;
 			throttled = false;
 			pr_info("OCC: Active\n");
+
+			for (i = 0; i < nr_chips; i++)
+				schedule_work(&chips[i].throttle);
+
 			return 0;
 		}

@@ -476,6 +492,12 @@ static int powernv_cpufreq_occ_msg(struct notifier_block *nb,
 		else if (!reason)
 			pr_info("OCC: Chip %u %s\n", (unsigned int)chip_id,
 				throttle_reason[reason]);
+		else
+			return 0;

Why the else section ? The code can never reach here, can it ?

When reason > 5 , we dont want to handle it.

Of course! My bad!

quoted

quoted

+
+		for (i = 0; i < nr_chips; i++)
+			if (chips[i].id == chip_id)
+				schedule_work(&chips[i].throttle);
 	}

Should we not do this only when we get unthrottled so as to cross verify
if it is indeed the case ? In case of throttling notification, opal's
verdict is final and there is no need to cross verify right ?

Two reasons for invoking *throttle_check() on throttling:
1) We just got to know the reason and not the Pmax value we are getting
throttled to.
2) It could be a spurious message caused due to late/lost delivery. My point
here is let us not completely rely on the notification to declare throttling
unless we verify it from reading PMSR.

Sounds good.

Regards
Preeti U Murthy