From: Mikulas Patocka Date: Mon, 9 Feb 2015 18:38:17 +0000 (-0500) Subject: cpufreq: speedstep-smi: enable interrupts when waiting X-Git-Tag: v3.2.69~187 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=dc4dc270e30142f941c00f975dfb85a3a332592a cpufreq: speedstep-smi: enable interrupts when waiting commit d4d4eda23794c701442e55129dd4f8f2fefd5e4d upstream. On Dell Latitude C600 laptop with Pentium 3 850MHz processor, the speedstep-smi driver sometimes loads and sometimes doesn't load with "change to state X failed" message. The hardware sometimes refuses to change frequency and in this case, we need to retry later. I found out that we need to enable interrupts while waiting. When we enable interrupts, the hardware blockage that prevents frequency transition resolves and the transition is possible. With disabled interrupts, the blockage doesn't resolve (no matter how long do we wait). The exact reasons for this hardware behavior are unknown. This patch enables interrupts in the function speedstep_set_state that can be called with disabled interrupts. However, this function is called with disabled interrupts only from speedstep_get_freqs, so it shouldn't cause any problem. Signed-off-by: Mikulas Patocka Signed-off-by: Rafael J. Wysocki Signed-off-by: Ben Hutchings --- diff --git a/drivers/cpufreq/speedstep-lib.c b/drivers/cpufreq/speedstep-lib.c index 8af2d2fd9d51..2c0345aee6d3 100644 --- a/drivers/cpufreq/speedstep-lib.c +++ b/drivers/cpufreq/speedstep-lib.c @@ -399,6 +399,7 @@ unsigned int speedstep_get_freqs(enum speedstep_processor processor, pr_debug("previous speed is %u\n", prev_speed); + preempt_disable(); local_irq_save(flags); /* switch to low state */ @@ -463,6 +464,8 @@ unsigned int speedstep_get_freqs(enum speedstep_processor processor, out: local_irq_restore(flags); + preempt_enable(); + return ret; } EXPORT_SYMBOL_GPL(speedstep_get_freqs); diff --git a/drivers/cpufreq/speedstep-smi.c b/drivers/cpufreq/speedstep-smi.c index c76ead3490bf..8a97f946a0cc 100644 --- a/drivers/cpufreq/speedstep-smi.c +++ b/drivers/cpufreq/speedstep-smi.c @@ -187,6 +187,7 @@ static void speedstep_set_state(unsigned int state) return; /* Disable IRQs */ + preempt_disable(); local_irq_save(flags); command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff); @@ -197,9 +198,19 @@ static void speedstep_set_state(unsigned int state) do { if (retry) { + /* + * We need to enable interrupts, otherwise the blockage + * won't resolve. + * + * We disable preemption so that other processes don't + * run. If other processes were running, they could + * submit more DMA requests, making the blockage worse. + */ pr_debug("retry %u, previous result %u, waiting...\n", retry, result); + local_irq_enable(); mdelay(retry * 50); + local_irq_disable(); } retry++; __asm__ __volatile__( @@ -216,6 +227,7 @@ static void speedstep_set_state(unsigned int state) /* enable IRQs */ local_irq_restore(flags); + preempt_enable(); if (new_state == state) pr_debug("change to %u MHz succeeded after %u tries "