linux-kernel - [-mm patch] CPUfreq: Only check for transition latency on problematic governors

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Message-Id: <1186065486.18821.545.camel@queen.suse.de>
Date:	Thu, 02 Aug 2007 16:38:06 +0200
From:	Thomas Renninger <trenn@...e.de>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	Gabriel C <nix.or.die@...glemail.com>, davej@...emonkey.org.uk,
	Andrew Morton <akpm@...ux-foundation.org>,
	Miles Lane <miles.lane@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, cpufreq@...ts.linux.org.uk,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Subject: [-mm patch] CPUfreq: Only check for transition latency on
	problematic governors

On Thu, 2007-08-02 at 15:48 +0200, Adrian Bunk wrote:
> On Thu, Aug 02, 2007 at 02:28:06AM +0200, Gabriel C wrote:
> > Andrew Morton wrote:
> > > On Wed, 1 Aug 2007 16:31:46 -0700
> > > "Miles Lane" <miles.lane@...il.com> wrote:
> > > 
> > >>   LD      .tmp_vmlinux1
> > >> drivers/built-in.o: In function `__cpufreq_governor':
> > >> cpufreq.c:(.text+0xaf178): undefined reference to `cpufreq_gov_performance'
> > >> cpufreq.c:(.text+0xaf18a): undefined reference to `cpufreq_gov_performance'
> > >> make: *** [.tmp_vmlinux1] Error 1
> > > 
> > > One for Thomas, I expect.
> > 
> > Is this patch :
> > 
> > cpufreq-allow-ondemand-and-conservative-cpufreq-governors-to-be-used-as-default.patch
> > 
> > Reverting it here fixes the error.
> 
> Possible fix below.
Or this one.
Advantage: You can still have cpufreq core without the performance 
           governor built.
Disadvantage: The logic whether transition latency checks are
              needed/done is moved to Kconfig.
              Means, if you write a governor that has transition
              latency values above 0, you must let it depend on
              the performance governor in Kconfig.

Hope I got all .config possibilities with that one now.
Attached is also a replacement patch for this one:
cpufreq-allow-ondemand-and-conservative-cpufreq-governors-to-be-used-as-default.patch


CPUfreq: Only check for transition latency on problematic governors

Signed-off-by: Thomas Renninger <trenn@...e.de>
--

--- linux-2.6.23-rc1-mm2/include/linux/cpufreq.h	2007-08-02 16:01:36.000000000 +0200
+++ linux-2.6.23-rc1-mm2_fixed/include/linux/cpufreq.h	2007-08-02 15:21:28.000000000 +0200
@@ -299,8 +299,10 @@ static inline unsigned int cpufreq_get(u
   Performance governor is fallback governor if any other gov failed to
   auto load due latency restrictions
 */
+#ifdef CONFIG_CPU_FREQ_GOV_PERFORMANCE
 extern struct cpufreq_governor cpufreq_gov_performance;
 #define CPUFREQ_PERFORMANCE_GOVERNOR	(&cpufreq_gov_performance)
+#endif
 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE
 #define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_performance)
 #elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE)
--- linux-2.6.23-rc1-mm2/drivers/cpufreq/cpufreq.c	2007-08-02 16:01:35.000000000 +0200
+++ linux-2.6.23-rc1-mm2_fixed/drivers/cpufreq/cpufreq.c	2007-08-02 16:23:09.000000000 +0200
@@ -1484,17 +1484,30 @@ static int __cpufreq_governor(struct cpu
 					unsigned int event)
 {
 	int ret;
+
+	/* Only must be defined when default governor is known to have latency
+	   restrictions, like e.g. conservative or ondemand.
+	   That this is the case is already ensured in Kconfig
+	*/
+#ifdef CONFIG_CPU_FREQ_GOV_PERFORMANCE
 	struct cpufreq_governor *gov = CPUFREQ_PERFORMANCE_GOVERNOR;
+#else
+	struct cpufreq_governor *gov = NULL;
+#endif
 
 	if (policy->governor->max_transition_latency &&
 	    policy->cpuinfo.transition_latency >
 	    policy->governor->max_transition_latency) {
-		printk(KERN_WARNING "%s governor failed, too long"
-		       " transition latency of HW, fallback"
-		       " to %s governor\n",
-		       policy->governor->name,
-		       gov->name);
-		       policy->governor = gov;
+		if (!gov)
+			return -EINVAL;
+		else {
+			printk(KERN_WARNING "%s governor failed, too long"
+			       " transition latency of HW, fallback"
+			       " to %s governor\n",
+			       policy->governor->name,
+			       gov->name);
+			policy->governor = gov;
+		}
 	}
 
 	if (!try_module_get(policy->governor->owner))


View attachment "ondemand_default.patch" of type "text/x-patch" (10015 bytes)