diff mbox series

[1/2] acpi: cppc: add cpufreq device

Message ID 20201210142139.20490-1-yousaf.kaukab@suse.com
State New
Headers show
Series [1/2] acpi: cppc: add cpufreq device | expand

Commit Message

Mian Yousaf Kaukab Dec. 10, 2020, 2:21 p.m. UTC 
From: Mian Yousaf Kaukab <ykaukab@suse.de>

Since commit 28f06f770454 ("cppc_cpufreq: replace per-cpu structures with
lists"), cppc-cpufreq driver doesn't check availability of PSD data before
registering with cpufreq core. As a result on a ThunderX2 platform when
CPPC is disabled from BIOS, kernel log is spammed with following messages:

[  180.974166] CPPC Cpufreq: Error in acquiring _CPC/_PSD data for CPUxx

acpi_cppc_processor_probe() never succeed in this case because
acpi_evaluate_object_typed("_CPC") always returns AE_NOT_FOUND. When
cpufreq core calls cppc_cpufreq_cpu_init(), driver fails to obtain PSD data
and print error messages.

Convert cppc-cpufreq driver to a platform driver (done in a separate patch)
and add cppc-cpufreq device when acpi_cppc_processor_probe() succeeds.

Fixes: 28f06f770454 ("cppc_cpufreq: replace per-cpu structures with lists")
Reported-by: Petr Cervinka <pcervinka@suse.com>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 drivers/acpi/cppc_acpi.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

Comments

Ionela Voinescu Dec. 10, 2020, 3:02 p.m. UTC | #1 
Hi guys,

On Thursday 10 Dec 2020 at 15:32:09 (+0100), Rafael J. Wysocki wrote:
> On Thu, Dec 10, 2020 at 3:23 PM Mian Yousaf Kaukab
> <yousaf.kaukab@suse.com> wrote:
> >
> > From: Mian Yousaf Kaukab <ykaukab@suse.de>
> >
> > Since commit 28f06f770454 ("cppc_cpufreq: replace per-cpu structures with
> > lists"), cppc-cpufreq driver doesn't check availability of PSD data before
> > registering with cpufreq core. As a result on a ThunderX2 platform when
> > CPPC is disabled from BIOS, kernel log is spammed with following messages:
> >
> > [  180.974166] CPPC Cpufreq: Error in acquiring _CPC/_PSD data for CPUxx
> >
> > acpi_cppc_processor_probe() never succeed in this case because
> > acpi_evaluate_object_typed("_CPC") always returns AE_NOT_FOUND. When
> > cpufreq core calls cppc_cpufreq_cpu_init(), driver fails to obtain PSD data
> > and print error messages.
> >
> > Convert cppc-cpufreq driver to a platform driver (done in a separate patch)
> > and add cppc-cpufreq device when acpi_cppc_processor_probe() succeeds.
> 
> Honestly, I prefer to drop 28f06f770454 (along with its follower)
> instead of making this change.
> 
> > Fixes: 28f06f770454 ("cppc_cpufreq: replace per-cpu structures with lists")
> 

Sorry for introducing this, I though it was enough to bail out of cpu
init if _CPC entries are not present.

I'll defer to Rafael to decide whether to drop the patches or accept
alternative fixes, but I believe the rework of the data structures and
initialisation is useful.

As alternative fix, would it be okay to introduce a check function to
verify for !cpc_ptr, to be called in cppc_cpufreq_init()? In that case
the driver would not be registered if this check fails.

Thanks,
Ionela.

> Thanks!
Mian Yousaf Kaukab Dec. 10, 2020, 3:04 p.m. UTC | #2 
On Thu, Dec 10, 2020 at 03:32:09PM +0100, Rafael J. Wysocki wrote:
> On Thu, Dec 10, 2020 at 3:23 PM Mian Yousaf Kaukab
> <yousaf.kaukab@suse.com> wrote:
> >
> > Convert cppc-cpufreq driver to a platform driver (done in a separate patch)
> > and add cppc-cpufreq device when acpi_cppc_processor_probe() succeeds.
> 
> Honestly, I prefer to drop 28f06f770454 (along with its follower)
> instead of making this change.
> 
Even if we revert 28f06f770454 there is still one more small issue that these
patches fix. Currently, ACPI_PROCESSOR_DEVICE_HID is used to load cppc-cpufreq
module. In case when CPPC is disabled, some cycles will be wasted in loading
cppc-cpufreq module. The module will return error from the init call though
so no memory is wasted.

After converting to platform-driver, cppc-cpufreq module will only be loaded
when the platform-device is available.

BR,
Yousaf
Rafael J. Wysocki Dec. 10, 2020, 6:54 p.m. UTC | #3 
On Thu, Dec 10, 2020 at 6:23 PM Ionela Voinescu <ionela.voinescu@arm.com> wrote:
>
> Hi Rafael,
>
> On Thursday 10 Dec 2020 at 17:55:56 (+0100), Rafael J. Wysocki wrote:
> > On Thursday, December 10, 2020 4:04:40 PM CET Mian Yousaf Kaukab wrote:
> > > On Thu, Dec 10, 2020 at 03:32:09PM +0100, Rafael J. Wysocki wrote:
> > > > On Thu, Dec 10, 2020 at 3:23 PM Mian Yousaf Kaukab
> > > > <yousaf.kaukab@suse.com> wrote:
> > > > >
> > > > > Convert cppc-cpufreq driver to a platform driver (done in a separate patch)
> > > > > and add cppc-cpufreq device when acpi_cppc_processor_probe() succeeds.
> > > >
> > > > Honestly, I prefer to drop 28f06f770454 (along with its follower)
> > > > instead of making this change.
> > > >
> > > Even if we revert 28f06f770454 there is still one more small issue that these
> > > patches fix. Currently, ACPI_PROCESSOR_DEVICE_HID is used to load cppc-cpufreq
> > > module. In case when CPPC is disabled, some cycles will be wasted in loading
> > > cppc-cpufreq module. The module will return error from the init call though
> > > so no memory is wasted.
> > >
> > > After converting to platform-driver, cppc-cpufreq module will only be loaded
> > > when the platform-device is available.
> >
> > Even so, that issue is low-impact AFAICS and may be addressed later and I'd
> > rather not let known breakage go into the mainline.
> >
> > I'm going to do drop the problematic commit now and please work with Ionela
> > to produce a clean series of patches in the right order to avoid introducing
> > issues between them.
> >
>
> The following commit will be easy to drop:
> a37afa60de38  cppc_cpufreq: optimise memory allocation for HW and NONE coordination (2 weeks ago)
>
> 28f06f770454  will be more difficult to drop as it's embedded in the
> series, and removing that one will produce conflicts in the patches
> that follow it:
>
> f9f5baa8b2a8  ACPI: processor: fix NONE coordination for domain mapping failure (3 weeks ago)
> cdb4ae5de6f7  cppc_cpufreq: expose information on frequency domains (3 weeks ago)
> c783a4d94848  cppc_cpufreq: clarify support for coordination types (3 weeks ago)
> 3bd412fb2c7f  cppc_cpufreq: use policy->cpu as driver of frequency setting (3 weeks ago)
> 28f06f770454  cppc_cpufreq: replace per-cpu structures with lists (3 weeks ago)

I dropped the commits above along with a37afa60de38 (and regenerated
my pm-cpufreq branch).

> bb025fb6c276  cppc_cpufreq: simplify use of performance capabilities (3 weeks ago)
> 48ad8dc94032  cppc_cpufreq: clean up cpu, cpu_num and cpunum variable use (3 weeks ago)
> 63087265c288  cppc_cpufreq: fix misspelling, code style and readability issues (3 weeks ago)
>
> Let me know how you want to proceed and I can either send a replacement
> series or reverts with conflicts fixed.

Please feel free to resubmit with the issue at hand addressed.

Thanks!
diff mbox series

Patch

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 4e478f751ff7..adf9ca3be9fe 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -39,6 +39,7 @@ 
 #include <linux/ktime.h>
 #include <linux/rwsem.h>
 #include <linux/wait.h>
+#include <linux/platform_device.h>
 
 #include <acpi/cppc_acpi.h>
 
@@ -606,6 +607,23 @@  static bool is_cppc_supported(int revision, int num_ent)
 	return true;
 }
 
+static void add_cppc_cpufreq_dev(void)
+{
+	static bool already_added;
+
+	if (!already_added) {
+		struct platform_device *pdev;
+
+		pdev = platform_device_register_simple("cppc-cpufreq", -1,
+				NULL, 0);
+		if (IS_ERR(pdev))
+			pr_err("Couldn't register cppc-cpufreq err=%ld\n",
+					PTR_ERR(pdev));
+		else
+			already_added = true;
+	}
+}
+
 /*
  * An example CPC table looks like the following.
  *
@@ -815,6 +833,9 @@  int acpi_cppc_processor_probe(struct acpi_processor *pr)
 	}
 
 	kfree(output.pointer);
+
+	add_cppc_cpufreq_dev();
+
 	return 0;
 
 out_free: