| Message ID | alpine.LRH.2.02.1502091337090.18363@file01.intranet.prod.int.rdu2.redhat.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On 10 February 2015 at 02:38, Mikulas Patocka <mpatocka@redhat.com> wrote: > 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 <mpatocka@redhat.com > Cc: stable@vger.kernel.org > > --- > drivers/cpufreq/speedstep-lib.c | 3 +++ > drivers/cpufreq/speedstep-smi.c | 12 ++++++++++++ > 2 files changed, 15 insertions(+) It looks it was reviewed/Acked long time back, what happened then ? -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 11 Feb 2015, Viresh Kumar wrote: > On 10 February 2015 at 02:38, Mikulas Patocka <mpatocka@redhat.com> wrote: > > 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 <mpatocka@redhat.com > > Cc: stable@vger.kernel.org > > > > --- > > drivers/cpufreq/speedstep-lib.c | 3 +++ > > drivers/cpufreq/speedstep-smi.c | 12 ++++++++++++ > > 2 files changed, 15 insertions(+) > > It looks it was reviewed/Acked long time back, what happened > then ? I don't know. You acknowledged it, but didn't put it upstream. Mikulas -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wednesday, February 11, 2015 06:01:27 AM Mikulas Patocka wrote: > > On Wed, 11 Feb 2015, Viresh Kumar wrote: > > > On 10 February 2015 at 02:38, Mikulas Patocka <mpatocka@redhat.com> wrote: > > > 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 <mpatocka@redhat.com > > > Cc: stable@vger.kernel.org > > > > > > --- > > > drivers/cpufreq/speedstep-lib.c | 3 +++ > > > drivers/cpufreq/speedstep-smi.c | 12 ++++++++++++ > > > 2 files changed, 15 insertions(+) > > > > It looks it was reviewed/Acked long time back, what happened > > then ? > > I don't know. You acknowledged it, but didn't put it upstream. That's probably my fault then, because I didn't apply it. OK, I'll queue it up for the next pull request with an ACK from Viresh.
Index: linux-3.14-rc1/drivers/cpufreq/speedstep-smi.c =================================================================== --- linux-3.14-rc1.orig/drivers/cpufreq/speedstep-smi.c 2014-02-03 18:56:44.000000000 +0100 +++ linux-3.14-rc1/drivers/cpufreq/speedstep-smi.c 2014-02-03 19:06:21.000000000 +0100 @@ -156,6 +156,7 @@ static void speedstep_set_state(unsigned return; /* Disable IRQs */ + preempt_disable(); local_irq_save(flags); command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff); @@ -166,9 +167,19 @@ static void speedstep_set_state(unsigned 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__( @@ -185,6 +196,7 @@ static void speedstep_set_state(unsigned /* enable IRQs */ local_irq_restore(flags); + preempt_enable(); if (new_state == state) pr_debug("change to %u MHz succeeded after %u tries " Index: linux-3.14-rc1/drivers/cpufreq/speedstep-lib.c =================================================================== --- linux-3.14-rc1.orig/drivers/cpufreq/speedstep-lib.c 2014-02-03 18:54:39.000000000 +0100 +++ linux-3.14-rc1/drivers/cpufreq/speedstep-lib.c 2014-02-03 19:06:21.000000000 +0100 @@ -400,6 +400,7 @@ unsigned int speedstep_get_freqs(enum sp pr_debug("previous speed is %u\n", prev_speed); + preempt_disable(); local_irq_save(flags); /* switch to low state */ @@ -464,6 +465,8 @@ unsigned int speedstep_get_freqs(enum sp out: local_irq_restore(flags); + preempt_enable(); + return ret; } EXPORT_SYMBOL_GPL(speedstep_get_freqs);
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 <mpatocka@redhat.com Cc: stable@vger.kernel.org --- drivers/cpufreq/speedstep-lib.c | 3 +++ drivers/cpufreq/speedstep-smi.c | 12 ++++++++++++ 2 files changed, 15 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html