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Commit 3221e55b authored by Srivatsa S. Bhat's avatar Srivatsa S. Bhat Committed by Rafael J. Wysocki
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cpufreq: powernow-k6: 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-k6 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-k6 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-k6 driver, since they rightly belong to the cpufreq core.

(Note that during ->exit(), the powernow-k6 driver sets the frequency
 without any help from the cpufreq core. So add explicit calls to the
 _begin() and _end() APIs around that frequency transition alone, to take
 care of that special case. Also, add a missing 'break' statement there.)

Fixes: 12478cf0 (cpufreq: Make sure frequency transitions are serialized)
Signed-off-by: default avatarSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 237ede16

drivers/cpufreq/powernow-k6.c

+11 −9
Original line number Original line Diff line number Diff line
@@ -138,22 +138,14 @@ static void powernow_k6_set_cpu_multiplier(unsigned int best_i) 
static int powernow_k6_target(struct cpufreq_policy *policy,

static int powernow_k6_target(struct cpufreq_policy *policy,

		unsigned int best_i)

		unsigned int best_i)

{

{

	struct cpufreq_freqs freqs;





	if (clock_ratio[best_i].driver_data > max_multiplier) {

	if (clock_ratio[best_i].driver_data > max_multiplier) {

		printk(KERN_ERR PFX "invalid target frequency\n");

		printk(KERN_ERR PFX "invalid target frequency\n");

		return -EINVAL;

		return -EINVAL;

	}

	}





	freqs.old = busfreq * powernow_k6_get_cpu_multiplier();

	freqs.new = busfreq * clock_ratio[best_i].driver_data;



	cpufreq_freq_transition_begin(policy, &freqs);



	powernow_k6_set_cpu_multiplier(best_i);

	powernow_k6_set_cpu_multiplier(best_i);





	cpufreq_freq_transition_end(policy, &freqs, 0);



	return 0;

	return 0;

}

}
@@ -229,8 +221,18 @@ static int powernow_k6_cpu_exit(struct cpufreq_policy *policy) 
	unsigned int i;

	unsigned int i;





	for (i = 0; (clock_ratio[i].frequency != CPUFREQ_TABLE_END); i++) {

	for (i = 0; (clock_ratio[i].frequency != CPUFREQ_TABLE_END); i++) {

		if (clock_ratio[i].driver_data == max_multiplier)

		if (clock_ratio[i].driver_data == max_multiplier) {

			struct cpufreq_freqs freqs;



			freqs.old = policy->cur;

			freqs.new = clock_ratio[i].frequency;

			freqs.flags = 0;



			cpufreq_freq_transition_begin(policy, &freqs);

			powernow_k6_target(policy, i);

			powernow_k6_target(policy, i);

			cpufreq_freq_transition_end(policy, &freqs, 0);

			break;

		}

	}

	}

	return 0;

	return 0;

}

}