[PATCH V2 1/2] platform/x86/intel/pmc: Refactor platform resume functions to use cnl_resume()

[PATCH V2 1/2] platform/x86/intel/pmc: Refactor platform resume functions to use cnl_resume()

[David E. Box]

Several platform resume functions currently call pmc_core_send_ltr_ignore()
and pmc_core_resume_common(), both of which are already called by
cnl_resume(). Simplify the code by having these functions call cnl_resume()
directly.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
---

V2 - New patch. Split from V1

 drivers/platform/x86/intel/pmc/arl.c | 3 +--
 drivers/platform/x86/intel/pmc/lnl.c | 3 +--
 drivers/platform/x86/intel/pmc/mtl.c | 3 +--
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/x86/intel/pmc/arl.c b/drivers/platform/x86/intel/pmc/arl.c
index e10527c4e3e0..05dec4f5019f 100644
--- a/drivers/platform/x86/intel/pmc/arl.c
+++ b/drivers/platform/x86/intel/pmc/arl.c
@@ -687,9 +687,8 @@ static void arl_d3_fixup(void)
 static int arl_resume(struct pmc_dev *pmcdev)
 {
 	arl_d3_fixup();
-	pmc_core_send_ltr_ignore(pmcdev, 3, 0);
 
-	return pmc_core_resume_common(pmcdev);
+	return cnl_resume(pmcdev);
 }
 
 int arl_core_init(struct pmc_dev *pmcdev)
diff --git a/drivers/platform/x86/intel/pmc/lnl.c b/drivers/platform/x86/intel/pmc/lnl.c
index e7a8077d1a3e..be029f12cdf4 100644
--- a/drivers/platform/x86/intel/pmc/lnl.c
+++ b/drivers/platform/x86/intel/pmc/lnl.c
@@ -546,9 +546,8 @@ static void lnl_d3_fixup(void)
 static int lnl_resume(struct pmc_dev *pmcdev)
 {
 	lnl_d3_fixup();
-	pmc_core_send_ltr_ignore(pmcdev, 3, 0);
 
-	return pmc_core_resume_common(pmcdev);
+	return cnl_resume(pmcdev);
 }
 
 int lnl_core_init(struct pmc_dev *pmcdev)
diff --git a/drivers/platform/x86/intel/pmc/mtl.c b/drivers/platform/x86/intel/pmc/mtl.c
index 91f2fa728f5c..fc6a89b8979f 100644
--- a/drivers/platform/x86/intel/pmc/mtl.c
+++ b/drivers/platform/x86/intel/pmc/mtl.c
@@ -988,9 +988,8 @@ static void mtl_d3_fixup(void)
 static int mtl_resume(struct pmc_dev *pmcdev)
 {
 	mtl_d3_fixup();
-	pmc_core_send_ltr_ignore(pmcdev, 3, 0);
 
-	return pmc_core_resume_common(pmcdev);
+	return cnl_resume(pmcdev);
 }
 
 int mtl_core_init(struct pmc_dev *pmcdev)

base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
-- 
2.43.0

[PATCH V2 2/2] platform/x86/intel/pmc: Disable C1 auto-demotion during suspend

[David E. Box]

On some platforms, aggressive C1 auto-demotion may lead to failure to enter
the deepest C-state during suspend-to-idle, causing high power consumption.
To prevent this, disable C1 auto-demotion during suspend and re-enable on
resume.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
---

V2 - Remove #define DEBUG
   - Move refactor of cnl_resume() to separate patch
   - Use smp_call_function() to disable and restore C1_AUTO_DEMOTE
   - Add comment that the MSR is per core, not per package.
   - Add comment that the online cpu mask remains unchanged during
     suspend due to frozen userspace.

 drivers/platform/x86/intel/pmc/cnp.c | 53 ++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/drivers/platform/x86/intel/pmc/cnp.c b/drivers/platform/x86/intel/pmc/cnp.c
index 513c02670c5a..f12d4f0f9e93 100644
--- a/drivers/platform/x86/intel/pmc/cnp.c
+++ b/drivers/platform/x86/intel/pmc/cnp.c
@@ -8,6 +8,8 @@
  *
  */
 
+#include <linux/smp.h>
+#include <linux/suspend.h>
 #include "core.h"
 
 /* Cannon Lake: PGD PFET Enable Ack Status Register(s) bitmap */
@@ -206,8 +208,52 @@ const struct pmc_reg_map cnp_reg_map = {
 	.etr3_offset = ETR3_OFFSET,
 };
 
+
+/*
+ * Disable C1 auto-demotion
+ *
+ * Aggressive C1 auto-demotion may lead to failure to enter the deepest C-state
+ * during suspend-to-idle, causing high power consumption. To prevent this, we
+ * disable C1 auto-demotion during suspend and re-enable on resume.
+ *
+ * Note that, although MSR_PKG_CST_CONFIG_CONTROL has 'package' in its name, it
+ * is actually a per-core MSR on client platforms, affecting only a single CPU.
+ * Therefore, it must be configured on all online CPUs. The online cpu mask is
+ * unchanged during the phase of suspend/resume as user space is frozen.
+ */
+
+static DEFINE_PER_CPU(u64, pkg_cst_config);
+
+static void disable_c1_auto_demote(void *unused)
+{
+	int cpunum = smp_processor_id();
+	u64 val;
+
+	rdmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
+	per_cpu(pkg_cst_config, cpunum) = val;
+	val &= ~NHM_C1_AUTO_DEMOTE;
+	wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
+	pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum, val);
+}
+
+static void restore_c1_auto_demote(void *unused)
+{
+	int cpunum = smp_processor_id();
+
+	pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum,
+		 per_cpu(pkg_cst_config, cpunum));
+	wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, per_cpu(pkg_cst_config, cpunum));
+}
+
 void cnl_suspend(struct pmc_dev *pmcdev)
 {
+	if (!pm_suspend_via_firmware()) {
+		preempt_disable();
+		disable_c1_auto_demote(NULL);
+		smp_call_function(disable_c1_auto_demote, NULL, 0);
+		preempt_enable();
+	}
+
 	/*
 	 * Due to a hardware limitation, the GBE LTR blocks PC10
 	 * when a cable is attached. To unblock PC10 during suspend,
@@ -218,6 +264,13 @@ void cnl_suspend(struct pmc_dev *pmcdev)
 
 int cnl_resume(struct pmc_dev *pmcdev)
 {
+	if (!pm_suspend_via_firmware()) {
+		preempt_disable();
+		restore_c1_auto_demote(NULL);
+		smp_call_function(restore_c1_auto_demote, NULL, 0);
+		preempt_enable();
+	}
+
 	pmc_core_send_ltr_ignore(pmcdev, 3, 0);
 
 	return pmc_core_resume_common(pmcdev);
-- 
2.43.0

Re: [PATCH V2 2/2] platform/x86/intel/pmc: Disable C1 auto-demotion during suspend

[srinivas pandruvada]

On Thu, 2024-10-10 at 17:36 -0700, David E. Box wrote:
> On some platforms, aggressive C1 auto-demotion may lead to failure to
> enter
> the deepest C-state during suspend-to-idle, causing high power
> consumption.
> To prevent this, disable C1 auto-demotion during suspend and re-
> enable on
> resume.
> 
> Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> ---
> 
> V2 - Remove #define DEBUG
>    - Move refactor of cnl_resume() to separate patch
>    - Use smp_call_function() to disable and restore C1_AUTO_DEMOTE
>    - Add comment that the MSR is per core, not per package.
>    - Add comment that the online cpu mask remains unchanged during
>      suspend due to frozen userspace.
> 
>  drivers/platform/x86/intel/pmc/cnp.c | 53
> ++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/drivers/platform/x86/intel/pmc/cnp.c
> b/drivers/platform/x86/intel/pmc/cnp.c
> index 513c02670c5a..f12d4f0f9e93 100644
> --- a/drivers/platform/x86/intel/pmc/cnp.c
> +++ b/drivers/platform/x86/intel/pmc/cnp.c
> @@ -8,6 +8,8 @@
>   *
>   */
>  
> +#include <linux/smp.h>
> +#include <linux/suspend.h>
>  #include "core.h"
>  
>  /* Cannon Lake: PGD PFET Enable Ack Status Register(s) bitmap */
> @@ -206,8 +208,52 @@ const struct pmc_reg_map cnp_reg_map = {
>  	.etr3_offset = ETR3_OFFSET,
>  };
>  
> +
> +/*
> + * Disable C1 auto-demotion
> + *
> + * Aggressive C1 auto-demotion may lead to failure to enter the
> deepest C-state
> + * during suspend-to-idle, causing high power consumption. To
> prevent this, we
> + * disable C1 auto-demotion during suspend and re-enable on resume.
> + *
> + * Note that, although MSR_PKG_CST_CONFIG_CONTROL has 'package' in
> its name, it
> + * is actually a per-core MSR on client platforms, affecting only a
> single CPU.
> + * Therefore, it must be configured on all online CPUs. The online
> cpu mask is
> + * unchanged during the phase of suspend/resume as user space is
> frozen.
> + */
> +
> +static DEFINE_PER_CPU(u64, pkg_cst_config);
> +
> +static void disable_c1_auto_demote(void *unused)
> +{
> +	int cpunum = smp_processor_id();
> +	u64 val;
> +
> +	rdmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
> +	per_cpu(pkg_cst_config, cpunum) = val;
> +	val &= ~NHM_C1_AUTO_DEMOTE;
> +	wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
> +	pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum, val);
Do you want to leave pr_debug?

> +}
> +
> +static void restore_c1_auto_demote(void *unused)
> +{
> +	int cpunum = smp_processor_id();
> +
> +	pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum,
> +		 per_cpu(pkg_cst_config, cpunum));
> +	wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, per_cpu(pkg_cst_config,
> cpunum));
> +}
> +
>  void cnl_suspend(struct pmc_dev *pmcdev)
>  {
> +	if (!pm_suspend_via_firmware()) {
> +		preempt_disable();
Why do you need this?


Thanks,
Srinivas

> +		disable_c1_auto_demote(NULL);
> +		smp_call_function(disable_c1_auto_demote, NULL, 0);
> +		preempt_enable();
> +	}
> +
>  	/*
>  	 * Due to a hardware limitation, the GBE LTR blocks PC10
>  	 * when a cable is attached. To unblock PC10 during suspend,
> @@ -218,6 +264,13 @@ void cnl_suspend(struct pmc_dev *pmcdev)
>  
>  int cnl_resume(struct pmc_dev *pmcdev)
>  {
> +	if (!pm_suspend_via_firmware()) {
> +		preempt_disable();
> +		restore_c1_auto_demote(NULL);
> +		smp_call_function(restore_c1_auto_demote, NULL, 0);
> +		preempt_enable();
> +	}
> +
>  	pmc_core_send_ltr_ignore(pmcdev, 3, 0);
>  
>  	return pmc_core_resume_common(pmcdev);

Re: [PATCH V2 2/2] platform/x86/intel/pmc: Disable C1 auto-demotion during suspend

[David E. Box]

On Thu, 2024-10-10 at 19:09 -0700, srinivas pandruvada wrote:
> On Thu, 2024-10-10 at 17:36 -0700, David E. Box wrote:
> > On some platforms, aggressive C1 auto-demotion may lead to failure to
> > enter
> > the deepest C-state during suspend-to-idle, causing high power
> > consumption.
> > To prevent this, disable C1 auto-demotion during suspend and re-
> > enable on
> > resume.
> > 
> > Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> > ---
> > 
> > V2 - Remove #define DEBUG
> >    - Move refactor of cnl_resume() to separate patch
> >    - Use smp_call_function() to disable and restore C1_AUTO_DEMOTE
> >    - Add comment that the MSR is per core, not per package.
> >    - Add comment that the online cpu mask remains unchanged during
> >      suspend due to frozen userspace.
> > 
> >  drivers/platform/x86/intel/pmc/cnp.c | 53
> > ++++++++++++++++++++++++++++
> >  1 file changed, 53 insertions(+)
> > 
> > diff --git a/drivers/platform/x86/intel/pmc/cnp.c
> > b/drivers/platform/x86/intel/pmc/cnp.c
> > index 513c02670c5a..f12d4f0f9e93 100644
> > --- a/drivers/platform/x86/intel/pmc/cnp.c
> > +++ b/drivers/platform/x86/intel/pmc/cnp.c
> > @@ -8,6 +8,8 @@
> >   *
> >   */
> >  
> > +#include <linux/smp.h>
> > +#include <linux/suspend.h>
> >  #include "core.h"
> >  
> >  /* Cannon Lake: PGD PFET Enable Ack Status Register(s) bitmap */
> > @@ -206,8 +208,52 @@ const struct pmc_reg_map cnp_reg_map = {
> >  	.etr3_offset = ETR3_OFFSET,
> >  };
> >  
> > +
> > +/*
> > + * Disable C1 auto-demotion
> > + *
> > + * Aggressive C1 auto-demotion may lead to failure to enter the
> > deepest C-state
> > + * during suspend-to-idle, causing high power consumption. To
> > prevent this, we
> > + * disable C1 auto-demotion during suspend and re-enable on resume.
> > + *
> > + * Note that, although MSR_PKG_CST_CONFIG_CONTROL has 'package' in
> > its name, it
> > + * is actually a per-core MSR on client platforms, affecting only a
> > single CPU.
> > + * Therefore, it must be configured on all online CPUs. The online
> > cpu mask is
> > + * unchanged during the phase of suspend/resume as user space is
> > frozen.
> > + */
> > +
> > +static DEFINE_PER_CPU(u64, pkg_cst_config);
> > +
> > +static void disable_c1_auto_demote(void *unused)
> > +{
> > +	int cpunum = smp_processor_id();
> > +	u64 val;
> > +
> > +	rdmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
> > +	per_cpu(pkg_cst_config, cpunum) = val;
> > +	val &= ~NHM_C1_AUTO_DEMOTE;
> > +	wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
> > +	pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum, val);
> Do you want to leave pr_debug?

Thought it could be useful but it can be removed.

> 
> > +}
> > +
> > +static void restore_c1_auto_demote(void *unused)
> > +{
> > +	int cpunum = smp_processor_id();
> > +
> > +	pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum,
> > +		 per_cpu(pkg_cst_config, cpunum));
> > +	wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, per_cpu(pkg_cst_config,
> > cpunum));
> > +}
> > +
> >  void cnl_suspend(struct pmc_dev *pmcdev)
> >  {
> > +	if (!pm_suspend_via_firmware()) {
> > +		preempt_disable();
> Why do you need this?

To ensure that the cpu doesn't change between the next two calls.

David

> 
> 
> Thanks,
> Srinivas
> 
> > +		disable_c1_auto_demote(NULL);
> > +		smp_call_function(disable_c1_auto_demote, NULL, 0);
> > +		preempt_enable();
> > +	}
> > +
> >  	/*
> >  	 * Due to a hardware limitation, the GBE LTR blocks PC10
> >  	 * when a cable is attached. To unblock PC10 during suspend,
> > @@ -218,6 +264,13 @@ void cnl_suspend(struct pmc_dev *pmcdev)
> >  
> >  int cnl_resume(struct pmc_dev *pmcdev)
> >  {
> > +	if (!pm_suspend_via_firmware()) {
> > +		preempt_disable();
> > +		restore_c1_auto_demote(NULL);
> > +		smp_call_function(restore_c1_auto_demote, NULL, 0);
> > +		preempt_enable();
> > +	}
> > +
> >  	pmc_core_send_ltr_ignore(pmcdev, 3, 0);
> >  
> >  	return pmc_core_resume_common(pmcdev);
> 

Re: [PATCH V2 2/2] platform/x86/intel/pmc: Disable C1 auto-demotion during suspend

[Rafael J. Wysocki]

On Fri, Oct 11, 2024 at 2:36 AM David E. Box
<david.e.box@linux.intel.com> wrote:
>
> On some platforms, aggressive C1 auto-demotion may lead to failure to enter
> the deepest C-state during suspend-to-idle, causing high power consumption.
> To prevent this, disable C1 auto-demotion during suspend and re-enable on
> resume.
>
> Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> ---
>
> V2 - Remove #define DEBUG
>    - Move refactor of cnl_resume() to separate patch
>    - Use smp_call_function() to disable and restore C1_AUTO_DEMOTE
>    - Add comment that the MSR is per core, not per package.
>    - Add comment that the online cpu mask remains unchanged during
>      suspend due to frozen userspace.
>
>  drivers/platform/x86/intel/pmc/cnp.c | 53 ++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>
> diff --git a/drivers/platform/x86/intel/pmc/cnp.c b/drivers/platform/x86/intel/pmc/cnp.c
> index 513c02670c5a..f12d4f0f9e93 100644
> --- a/drivers/platform/x86/intel/pmc/cnp.c
> +++ b/drivers/platform/x86/intel/pmc/cnp.c
> @@ -8,6 +8,8 @@
>   *
>   */
>
> +#include <linux/smp.h>
> +#include <linux/suspend.h>
>  #include "core.h"
>
>  /* Cannon Lake: PGD PFET Enable Ack Status Register(s) bitmap */
> @@ -206,8 +208,52 @@ const struct pmc_reg_map cnp_reg_map = {
>         .etr3_offset = ETR3_OFFSET,
>  };
>
> +
> +/*
> + * Disable C1 auto-demotion
> + *
> + * Aggressive C1 auto-demotion may lead to failure to enter the deepest C-state
> + * during suspend-to-idle, causing high power consumption. To prevent this, we
> + * disable C1 auto-demotion during suspend and re-enable on resume.
> + *
> + * Note that, although MSR_PKG_CST_CONFIG_CONTROL has 'package' in its name, it
> + * is actually a per-core MSR on client platforms, affecting only a single CPU.
> + * Therefore, it must be configured on all online CPUs. The online cpu mask is
> + * unchanged during the phase of suspend/resume as user space is frozen.
> + */
> +
> +static DEFINE_PER_CPU(u64, pkg_cst_config);
> +
> +static void disable_c1_auto_demote(void *unused)
> +{
> +       int cpunum = smp_processor_id();
> +       u64 val;
> +
> +       rdmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
> +       per_cpu(pkg_cst_config, cpunum) = val;
> +       val &= ~NHM_C1_AUTO_DEMOTE;
> +       wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
> +       pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum, val);
> +}

If you decide to retain the debug statements, I generally prefer to
separate them from the rest of the code with empty lines, for clarity.

> +
> +static void restore_c1_auto_demote(void *unused)
> +{
> +       int cpunum = smp_processor_id();
> +
> +       pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum,
> +                per_cpu(pkg_cst_config, cpunum));
> +       wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, per_cpu(pkg_cst_config, cpunum));
> +}
> +

I would add something like

static void s2idle_cpu_quirk(smp_call_func_t func)
{
       if (pm_suspend_via_firmware())
              return;

       preempt_disable();
       func();
       smp_call_function(func, NULL, 0);
       preempt_enable();
}

>  void cnl_suspend(struct pmc_dev *pmcdev)
>  {
> +       if (!pm_suspend_via_firmware()) {
> +               preempt_disable();
> +               disable_c1_auto_demote(NULL);
> +               smp_call_function(disable_c1_auto_demote, NULL, 0);
> +               preempt_enable();
> +       }
> +

And here I'd just do

      s2idle_cpu_quirk(disable_c1_auto_demote);

and analogously below.

>         /*
>          * Due to a hardware limitation, the GBE LTR blocks PC10
>          * when a cable is attached. To unblock PC10 during suspend,
> @@ -218,6 +264,13 @@ void cnl_suspend(struct pmc_dev *pmcdev)
>
>  int cnl_resume(struct pmc_dev *pmcdev)
>  {
> +       if (!pm_suspend_via_firmware()) {
> +               preempt_disable();
> +               restore_c1_auto_demote(NULL);
> +               smp_call_function(restore_c1_auto_demote, NULL, 0);
> +               preempt_enable();
> +       }
> +
>         pmc_core_send_ltr_ignore(pmcdev, 3, 0);
>
>         return pmc_core_resume_common(pmcdev);
> --

Re: [PATCH V2 2/2] platform/x86/intel/pmc: Disable C1 auto-demotion during suspend

[srinivas pandruvada]

On Thu, 2024-10-10 at 20:50 -0700, David E. Box wrote:
> On Thu, 2024-10-10 at 19:09 -0700, srinivas pandruvada wrote:
> > On Thu, 2024-10-10 at 17:36 -0700, David E. Box wrote:
> > > On some platforms, aggressive C1 auto-demotion may lead to
> > > failure to
> > > enter
> > > the deepest C-state during suspend-to-idle, causing high power
> > > consumption.
> > > To prevent this, disable C1 auto-demotion during suspend and re-
> > > enable on
> > > resume.
> > > 
> > > Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> > > ---
> > > 
> > > V2 - Remove #define DEBUG
> > >    - Move refactor of cnl_resume() to separate patch
> > >    - Use smp_call_function() to disable and restore
> > > C1_AUTO_DEMOTE
> > >    - Add comment that the MSR is per core, not per package.
> > >    - Add comment that the online cpu mask remains unchanged
> > > during
> > >      suspend due to frozen userspace.
> > > 
> > >  drivers/platform/x86/intel/pmc/cnp.c | 53
> > > ++++++++++++++++++++++++++++
> > >  1 file changed, 53 insertions(+)
> > > 
> > > diff --git a/drivers/platform/x86/intel/pmc/cnp.c
> > > b/drivers/platform/x86/intel/pmc/cnp.c
> > > index 513c02670c5a..f12d4f0f9e93 100644
> > > --- a/drivers/platform/x86/intel/pmc/cnp.c
> > > +++ b/drivers/platform/x86/intel/pmc/cnp.c
> > > @@ -8,6 +8,8 @@
> > >   *
> > >   */
> > >  
> > > +#include <linux/smp.h>
> > > +#include <linux/suspend.h>
> > >  #include "core.h"
> > >  
> > >  /* Cannon Lake: PGD PFET Enable Ack Status Register(s) bitmap */
> > > @@ -206,8 +208,52 @@ const struct pmc_reg_map cnp_reg_map = {
> > >  	.etr3_offset = ETR3_OFFSET,
> > >  };
> > >  
> > > +
> > > +/*
> > > + * Disable C1 auto-demotion
> > > + *
> > > + * Aggressive C1 auto-demotion may lead to failure to enter the
> > > deepest C-state
> > > + * during suspend-to-idle, causing high power consumption. To
> > > prevent this, we
> > > + * disable C1 auto-demotion during suspend and re-enable on
> > > resume.
> > > + *
> > > + * Note that, although MSR_PKG_CST_CONFIG_CONTROL has 'package'
> > > in
> > > its name, it
> > > + * is actually a per-core MSR on client platforms, affecting
> > > only a
> > > single CPU.
> > > + * Therefore, it must be configured on all online CPUs. The
> > > online
> > > cpu mask is
> > > + * unchanged during the phase of suspend/resume as user space is
> > > frozen.
> > > + */
> > > +
> > > +static DEFINE_PER_CPU(u64, pkg_cst_config);
> > > +
> > > +static void disable_c1_auto_demote(void *unused)
> > > +{
> > > +	int cpunum = smp_processor_id();
> > > +	u64 val;
> > > +
> > > +	rdmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
> > > +	per_cpu(pkg_cst_config, cpunum) = val;
> > > +	val &= ~NHM_C1_AUTO_DEMOTE;
> > > +	wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, val);
> > > +	pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum,
> > > val);
> > Do you want to leave pr_debug?
> 
> Thought it could be useful but it can be removed.
> 
> > 
> > > +}
> > > +
> > > +static void restore_c1_auto_demote(void *unused)
> > > +{
> > > +	int cpunum = smp_processor_id();
> > > +
> > > +	pr_debug("%s: cpu:%d cst %llx\n", __func__, cpunum,
> > > +		 per_cpu(pkg_cst_config, cpunum));
> > > +	wrmsrl(MSR_PKG_CST_CONFIG_CONTROL,
> > > per_cpu(pkg_cst_config,
> > > cpunum));
> > > +}
> > > +
> > >  void cnl_suspend(struct pmc_dev *pmcdev)
> > >  {
> > > +	if (!pm_suspend_via_firmware()) {
> > > +		preempt_disable();
> > Why do you need this?
> 
> To ensure that the cpu doesn't change between the next two calls.

Correct. You need for smp_processor_id()

Generally for this avoiding issue with smp_processor_id(), you can use
get_cpu(), which gives current cpu as return value and also disable
preemption.

Something like this

                this_cpu = get_cpu();
                disable_c1_auto_demote(&this_cpu);
smp_call_function_many(cpu_online_mask, disable_c1_auto_demote, NULL,
0);
                put_cpu();


But fine, this makes your code more complex as you have to pass now a
param and use for local_cpu and use smp_procesor_id() for remote call
via smp_call..


Thanks,
Srinivas

> 
> David
> 
> > 
> > 
> > Thanks,
> > Srinivas
> > 
> > > +		disable_c1_auto_demote(NULL);
> > > +		smp_call_function(disable_c1_auto_demote, NULL,
> > > 0);
> > > +		preempt_enable();
> > > +	}
> > > +
> > >  	/*
> > >  	 * Due to a hardware limitation, the GBE LTR blocks PC10
> > >  	 * when a cable is attached. To unblock PC10 during
> > > suspend,
> > > @@ -218,6 +264,13 @@ void cnl_suspend(struct pmc_dev *pmcdev)
> > >  
> > >  int cnl_resume(struct pmc_dev *pmcdev)
> > >  {
> > > +	if (!pm_suspend_via_firmware()) {
> > > +		preempt_disable();
> > > +		restore_c1_auto_demote(NULL);
> > > +		smp_call_function(restore_c1_auto_demote, NULL,
> > > 0);
> > > +		preempt_enable();
> > > +	}
> > > +
> > >  	pmc_core_send_ltr_ignore(pmcdev, 3, 0);
> > >  
> > >  	return pmc_core_resume_common(pmcdev);
> > 
> 
> 

Re: [PATCH V2 2/2] platform/x86/intel/pmc: Disable C1 auto-demotion during suspend

[srinivas pandruvada]

+Ricardo

On Thu, 2024-10-10 at 17:36 -0700, David E. Box wrote:
> On some platforms, aggressive C1 auto-demotion may lead to failure to
> enter
> the deepest C-state during suspend-to-idle, causing high power
> consumption.
> To prevent this, disable C1 auto-demotion during suspend and re-
> enable on
> resume.
> 
> Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> ---
> 

[...]


>  void cnl_suspend(struct pmc_dev *pmcdev)
>  {
> +	if (!pm_suspend_via_firmware()) {
> +		preempt_disable();
> +		disable_c1_auto_demote(NULL);
> +		smp_call_function(disable_c1_auto_demote, NULL, 0);
> +		preempt_enable();
> +	}
> 
As suggested by Ricardo using the following will work avoiding separate
local CPU call. Preemption will be disabled, no need separate call.
Also cpu_online_mask can't be changed during these callbacks.

if (!pm_suspend_via_firmware())
	on_each_cpu(disable_c1_auto_demote, NULL, true);

I think you need wait=true. I have seen on some occasions you will miss
msr write as we called mwait before before async calls finished. 


Thanks,
Srinivas

> +
>  	/*
>  	 * Due to a hardware limitation, the GBE LTR blocks PC10
>  	 * when a cable is attached. To unblock PC10 during suspend,
> @@ -218,6 +264,13 @@ void cnl_suspend(struct pmc_dev *pmcdev)
>  
>  int cnl_resume(struct pmc_dev *pmcdev)
>  {
> +	if (!pm_suspend_via_firmware()) {
> +		preempt_disable();
> +		restore_c1_auto_demote(NULL);
> +		smp_call_function(restore_c1_auto_demote, NULL, 0);
> +		preempt_enable();
> +	}
> +
>  	pmc_core_send_ltr_ignore(pmcdev, 3, 0);
>  
>  	return pmc_core_resume_common(pmcdev);