[PATCH] support for CPUFREQ_ETERNAL drivers by the ondemand governor

From: Eric Piel <Eric.Piel@tremplin-utc.net>
To: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
	Jun Nakajima <jun.nakajima@intel.com>
Cc: cpufreq@lists.linux.org.uk
Subject: [PATCH] support for CPUFREQ_ETERNAL drivers by the ondemand governor
Date: Sun, 06 Feb 2005 23:33:49 +0100	[thread overview]
Message-ID: <42069B4D.6090505@tremplin-utc.net> (raw)

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Hello,

For now the ondemand governor doesn't support the drivers which reports 
a transition latency of CPUFREQ_ETERNAL. That's really a problem because 
most of the drivers declare such a latency (simply because it's not 
known, not really because the transition will take an eternal time). 
All userspace daemons suport those drivers, they just don't pay 
attention to the transition latency.

This patch proposes to consider a CPUFREQ_ETERNAL latency as the maximum 
possible latency of the governor (10 ms). I think this should be 
conservative enough to be safe with any driver.

Hoping you like it,
Eric

--
Support for CPUFREQ_ETERNAL drivers by the ondemand governor.

Signed-off-by: Eric Piel <eric.piel@tremplin-utc.net>
--

[-- Attachment #2: ondemand-accept-eternel-transition-latency-2.6.11-rc3.patch --]
[-- Type: text/x-patch, Size: 1345 bytes --]

--- linux-2.6.11-rc3/drivers/cpufreq/cpufreq_ondemand.c.orig	2005-02-05 17:09:30.000000000 +0100
+++ linux-2.6.11-rc3/drivers/cpufreq/cpufreq_ondemand.c	2005-02-05 18:02:55.000000000 +0100
@@ -56,7 +56,7 @@ static unsigned int 				def_sampling_rat
 #define MAX_SAMPLING_RATE			(500 * def_sampling_rate)
 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER	(1000)
 #define DEF_SAMPLING_DOWN_FACTOR		(10)
-#define TRANSITION_LATENCY_LIMIT		(10 * 1000)
+#define TRANSITION_LATENCY_LIMIT		(10 * 1000 * 1000) /* ns */
 #define sampling_rate_in_HZ(x)			(((x * HZ) < (1000 * 1000))?1:((x * HZ) / (1000 * 1000)))
 
 static void do_dbs_timer(void *data);
@@ -385,8 +385,8 @@ static int cpufreq_governor_dbs(struct c
 		    (!policy->cur))
 			return -EINVAL;
 
-		if (policy->cpuinfo.transition_latency >
-				(TRANSITION_LATENCY_LIMIT * 1000))
+		if ((policy->cpuinfo.transition_latency > TRANSITION_LATENCY_LIMIT) &&
+		    (policy->cpuinfo.transition_latency != CPUFREQ_ETERNAL))
 			return -EINVAL;
 		if (this_dbs_info->enable) /* Already enabled */
 			break;
@@ -416,6 +416,8 @@ static int cpufreq_governor_dbs(struct c
 			/* policy latency is in nS. Convert it to uS first */
 
 			latency = policy->cpuinfo.transition_latency;
+			if (latency == CPUFREQ_ETERNAL)
+				latency = TRANSITION_LATENCY_LIMIT;
 			if (latency < 1000)
 				latency = 1000;
 

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