linux-kernel - [PATCH] cpufreq: set value of CPUFREQ_BOOST

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Date:	Mon, 24 Mar 2014 12:18:14 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	rjw@...ysocki.net
Cc:	linaro-kernel@...ts.linaro.org, cpufreq@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	srivatsa.bhat@...ux.vnet.ibm.com, ego@...ux.vnet.ibm.com,
	svaidy@...ux.vnet.ibm.com, l.majewski@...sung.com,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: [PATCH] cpufreq: set value of CPUFREQ_BOOST_FREQ to 0xABABABAB

Ideally, .driver_data field of struct cpufreq_frequency_table must not be used
by core at all. But during a recent change if its value is same as
CPUFREQ_BOOST_FREQ macro, then it is treated specially by core.

The value of this macro was set to ~2 earlier, i.e. 0xFFFFFFFD. In case some
driver is using this field for its own data and sets this field to -3, then with
two's complement that value will also become 0xFFFFFFFD.

To fix this issue, lets change value of this flag to a very uncommon value which
shouldn't be used by any driver unless they want to use BOOST feature.

Along with this update comments to make this more clear.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---

Gautham/Vaidy: I hope this fixes the problem we discussed for your patchset.

 include/linux/cpufreq.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index c48e595..9f25d9d 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -455,12 +455,18 @@ extern struct cpufreq_governor cpufreq_gov_conservative;
  *                     FREQUENCY TABLE HELPERS                       *
  *********************************************************************/
 
+/* Special Values of .frequency field */
 #define CPUFREQ_ENTRY_INVALID ~0
 #define CPUFREQ_TABLE_END     ~1
-#define CPUFREQ_BOOST_FREQ    ~2
+/* Special Values of .driver_data field */
+#define CPUFREQ_BOOST_FREQ    0xABABABAB
 
 struct cpufreq_frequency_table {
-	unsigned int	driver_data; /* driver specific data, not used by core */
+	/*
+	 * driver specific data, not used by core unless it is set to
+	 * CPUFREQ_BOOST_FREQ.
+	 */
+	unsigned int	driver_data;
 	unsigned int	frequency; /* kHz - doesn't need to be in ascending
 				    * order */
 };
-- 
1.7.12.rc2.18.g61b472e

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