linux-kernel - [PATCH v2 4/5] cpufreq, powernow-k7: Fix double invocation of cpufreq_freq_transition

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Date:	Tue, 29 Apr 2014 00:24:58 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	rjw@...ysocki.net, mroos@...ux.ee, viresh.kumar@...aro.org
Cc:	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com
Subject: [PATCH v2 4/5] cpufreq, powernow-k7: Fix double invocation of
 cpufreq_freq_transition_begin/end

During frequency transitions, the cpufreq core takes the responsibility of
invoking cpufreq_freq_transition_begin() and cpufreq_freq_transition_end()
for those cpufreq drivers that define the ->target_index callback but don't
set the ASYNC_NOTIFICATION flag.

The powernow-k7 cpufreq driver falls under this category, but this driver was
invoking the _begin() and _end() APIs itself around frequency transitions,
which led to double invocation of the _begin() API. The _begin API makes
contending callers wait until the previous invocation is complete. Hence,
the powernow-k7 driver ended up waiting on itself, leading to system hangs
during boot.

Fix this by removing the calls to the _begin() and _end() APIs from the
powernow-k7 driver, since they rightly belong to the cpufreq core.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
---

 drivers/cpufreq/powernow-k7.c |    4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/cpufreq/powernow-k7.c b/drivers/cpufreq/powernow-k7.c
index f911645..e61e224 100644
--- a/drivers/cpufreq/powernow-k7.c
+++ b/drivers/cpufreq/powernow-k7.c
@@ -269,8 +269,6 @@ static int powernow_target(struct cpufreq_policy *policy, unsigned int index)

 	freqs.new = powernow_table[index].frequency;

-	cpufreq_freq_transition_begin(policy, &freqs);
-
 	/* Now do the magic poking into the MSRs.  */

 	if (have_a0 == 1)	/* A0 errata 5 */
@@ -290,8 +288,6 @@ static int powernow_target(struct cpufreq_policy *policy, unsigned int index)
 	if (have_a0 == 1)
 		local_irq_enable();

-	cpufreq_freq_transition_end(policy, &freqs, 0);
-
 	return 0;
 }

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