diff mbox series

[RFC,v1,4/4] PCI/ASPM: Remove struct pcie_link_state.clkpm_disable

Message ID 20210929004400.25717-5-refactormyself@gmail.com (mailing list archive)
State Superseded
Delegated to: Bjorn Helgaas
Headers show
Series Remove struct pcie_link_state.clkpm_* | expand

Commit Message

Saheed O. Bolarinwa Sept. 29, 2021, 12:44 a.m. UTC 
From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>

The clkpm_disable member of the struct pcie_link_state indicates
if the Clock PM state of the device is disabled. There are two
situations which can cause the Clock PM state disabled.
1. If the device fails sanity check as in pcie_aspm_sanity_check()
2. By calling __pci_disable_link_state()

It is possible to set the Clock PM state of a device ON or OFF by
calling pcie_set_clkpm(). The state can be retieved by calling
pcie_get_clkpm_state().

pcie_link_state.clkpm_disable is only accessed in pcie_set_clkpm()
to ensure that Clock PM state can be reenabled after being disabled.

This patch:
  - add pm_disable to the struct pcie_link_state, to indicate that
    the kernel has marked the device's AS and Clock PM states disabled
  - removes clkpm_disable from the struct pcie_link_state
  - removes all instance where clkpm_disable is set
  - ensure that the Clock PM is always disabled if it is part of the
    states passed into __pci_disable_link_state(), regardless of the
    global policy

Signed-off-by: Bolarinwa O. Saheed <refactormyself@gmail.com>
---
 drivers/pci/pcie/aspm.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

Comments

Bjorn Helgaas Sept. 30, 2021, 8:20 p.m. UTC | #1 
On Wed, Sep 29, 2021 at 02:44:00AM +0200, Saheed O. Bolarinwa wrote:
> From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>
> 
> The clkpm_disable member of the struct pcie_link_state indicates
> if the Clock PM state of the device is disabled. There are two
> situations which can cause the Clock PM state disabled.
> 1. If the device fails sanity check as in pcie_aspm_sanity_check()
> 2. By calling __pci_disable_link_state()

And, 3. clkpm_store(), when the user writes to the "clkpm" sysfs file,
right?

IIUC, clkpm_disable really tells us whether we can enable clkpm.  The
only place we test clkpm_disable is in pcie_set_clkpm():

  pcie_set_clkpm(struct pcie_link_state *link, int enable)
  {
    if (!link->clkpm_capable || link->clkpm_disable)
      enable = 0;
    pcie_set_clkpm_nocheck(link, enable);
  }

So in other words, if clkpm_disable is set, we will never call
pcie_set_clkpm_nocheck() to *enable* clkpm.  We will only call it to
*disable* clkpm.

Tangent: I think the usefulness of pcie_set_clkpm_nocheck() being a
separate function is gone.  I think things will be a little simpler if
we integrate it into pcie_set_clkpm().  Separate preliminary patch, of
course.

> It is possible to set the Clock PM state of a device ON or OFF by
> calling pcie_set_clkpm(). The state can be retieved by calling
> pcie_get_clkpm_state().

s/retieved/retrieved/

> pcie_link_state.clkpm_disable is only accessed in pcie_set_clkpm()
> to ensure that Clock PM state can be reenabled after being disabled.
> 
> This patch:
>   - add pm_disable to the struct pcie_link_state, to indicate that
>     the kernel has marked the device's AS and Clock PM states disabled
>   - removes clkpm_disable from the struct pcie_link_state
>   - removes all instance where clkpm_disable is set
>   - ensure that the Clock PM is always disabled if it is part of the
>     states passed into __pci_disable_link_state(), regardless of the
>     global policy
> 
> Signed-off-by: Bolarinwa O. Saheed <refactormyself@gmail.com>
> ---
>  drivers/pci/pcie/aspm.c | 18 +++++-------------
>  1 file changed, 5 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 368828cd427d..e6ae00daa7ae 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -60,8 +60,7 @@ struct pcie_link_state {
>  	u32 aspm_default:7;		/* Default ASPM state by BIOS */
>  	u32 aspm_disable:7;		/* Disabled ASPM state */
>  
> -	/* Clock PM state */
> -	u32 clkpm_disable:1;		/* Clock PM disabled */
> +	u32 pm_disabled:1;		/* Disabled AS and Clock PM ? */

What did we gain by renaming this?  AFAICT this only affects clkpm
(the only test of pm_disabled is in pcie_set_clkpm()).

>  	/* Exit latencies */
>  	struct aspm_latency latency_up;	/* Upstream direction exit latency */
> @@ -198,7 +197,7 @@ static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
>  	 * Don't enable Clock PM if the link is not Clock PM capable
>  	 * or Clock PM is disabled
>  	 */
> -	if (!capable || link->clkpm_disable)
> +	if (enable && (!capable || link->pm_disabled))
>  		enable = 0;
>  	/* Need nothing if the specified equals to current state */
>  	if (pcie_get_clkpm_state(link->pdev) == enable)
> @@ -206,11 +205,6 @@ static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
>  	pcie_set_clkpm_nocheck(link, enable);
>  }
>  
> -static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
> -{
> -	link->clkpm_disable = blacklist ? 1 : 0;
> -}
> -
>  static bool pcie_retrain_link(struct pcie_link_state *link)
>  {
>  	struct pci_dev *parent = link->pdev;
> @@ -952,8 +946,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
>  	 */
>  	pcie_aspm_cap_init(link, blacklist);
>  
> -	/* Setup initial Clock PM state */
> -	pcie_clkpm_cap_init(link, blacklist);
> +	link->pm_disabled = blacklist;
>  
>  	/*
>  	 * At this stage drivers haven't had an opportunity to change the
> @@ -1129,8 +1122,8 @@ static int __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
>  	pcie_config_aspm_link(link, policy_to_aspm_state(link));
>  
>  	if (state & PCIE_LINK_STATE_CLKPM)
> -		link->clkpm_disable = 1;
> -	pcie_set_clkpm(link, policy_to_clkpm_state(link));
> +		pcie_set_clkpm(link, 0);
> +
>  	mutex_unlock(&aspm_lock);
>  	if (sem)
>  		up_read(&pci_bus_sem);
> @@ -1301,7 +1294,6 @@ static ssize_t clkpm_store(struct device *dev,
>  	down_read(&pci_bus_sem);
>  	mutex_lock(&aspm_lock);
>  
> -	link->clkpm_disable = !state_enable;

Something is seriously wrong here because clkpm_store() no longer does
anything with "state_enable", the value we got from the user.

>  	pcie_set_clkpm(link, policy_to_clkpm_state(link));
>  
>  	mutex_unlock(&aspm_lock);
> -- 
> 2.20.1
>
Saheed O. Bolarinwa Oct. 11, 2021, 6:06 a.m. UTC | #2 
Thank you for the review.


On Thu, Sep 30, 2021 at 10:20 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Wed, Sep 29, 2021 at 02:44:00AM +0200, Saheed O. Bolarinwa wrote:
> > From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>
> >
> > The clkpm_disable member of the struct pcie_link_state indicates
> > if the Clock PM state of the device is disabled. There are two
> > situations which can cause the Clock PM state disabled.
> > 1. If the device fails sanity check as in pcie_aspm_sanity_check()
> > 2. By calling __pci_disable_link_state()
>
> And, 3. clkpm_store(), when the user writes to the "clkpm" sysfs file,
> right?
That's right and something went wrong truly. I intend to propose that
instead of setting
    link->clkpm_disable = !state_enable;
we can :
    if (!state_enable)
         pci_disable_link_state_locked(pdev, PCIE_LINK_STATE_CLKPM);

>
> IIUC, clkpm_disable really tells us whether we can enable clkpm.  The
> only place we test clkpm_disable is in pcie_set_clkpm():
>
>   pcie_set_clkpm(struct pcie_link_state *link, int enable)
>   {
>     if (!link->clkpm_capable || link->clkpm_disable)
>       enable = 0;
>     pcie_set_clkpm_nocheck(link, enable);
>   }
>
> So in other words, if clkpm_disable is set, we will never call
> pcie_set_clkpm_nocheck() to *enable* clkpm.  We will only call it to
> *disable* clkpm.
>
For case 1 (as stated above), this is fine. However, I am concerned that
the intention of cases 2 and 3 may require that it should be possible to
re-enable clkpm after disabling it. Is this the correct perspective?

I think the essence of this patch should have been to show that cases 2 and 3
have the same goal which is different from case 1. Hence, three and not two
checks are needed within pcie_set_clkpm().




> Tangent: I think the usefulness of pcie_set_clkpm_nocheck() being a
> separate function is gone.  I think things will be a little simpler if
> we integrate it into pcie_set_clkpm().  Separate preliminary patch, of
> course.
>
> > It is possible to set the Clock PM state of a device ON or OFF by
> > calling pcie_set_clkpm(). The state can be retieved by calling
> > pcie_get_clkpm_state().
>
> s/retieved/retrieved/
>
> > pcie_link_state.clkpm_disable is only accessed in pcie_set_clkpm()
> > to ensure that Clock PM state can be reenabled after being disabled.
> >
> > This patch:
> >   - add pm_disable to the struct pcie_link_state, to indicate that
> >     the kernel has marked the device's AS and Clock PM states disabled
> >   - removes clkpm_disable from the struct pcie_link_state
> >   - removes all instance where clkpm_disable is set
> >   - ensure that the Clock PM is always disabled if it is part of the
> >     states passed into __pci_disable_link_state(), regardless of the
> >     global policy
> >
> > Signed-off-by: Bolarinwa O. Saheed <refactormyself@gmail.com>
> > ---
> >  drivers/pci/pcie/aspm.c | 18 +++++-------------
> >  1 file changed, 5 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index 368828cd427d..e6ae00daa7ae 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -60,8 +60,7 @@ struct pcie_link_state {
> >       u32 aspm_default:7;             /* Default ASPM state by BIOS */
> >       u32 aspm_disable:7;             /* Disabled ASPM state */
> >
> > -     /* Clock PM state */
> > -     u32 clkpm_disable:1;            /* Clock PM disabled */
> > +     u32 pm_disabled:1;              /* Disabled AS and Clock PM ? */
>
> What did we gain by renaming this?  AFAICT this only affects clkpm
> (the only test of pm_disabled is in pcie_set_clkpm()).
>
> >       /* Exit latencies */
> >       struct aspm_latency latency_up; /* Upstream direction exit latency */
> > @@ -198,7 +197,7 @@ static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
> >        * Don't enable Clock PM if the link is not Clock PM capable
> >        * or Clock PM is disabled
> >        */
> > -     if (!capable || link->clkpm_disable)
> > +     if (enable && (!capable || link->pm_disabled))
> >               enable = 0;
> >       /* Need nothing if the specified equals to current state */
> >       if (pcie_get_clkpm_state(link->pdev) == enable)
> > @@ -206,11 +205,6 @@ static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
> >       pcie_set_clkpm_nocheck(link, enable);
> >  }
> >
> > -static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
> > -{
> > -     link->clkpm_disable = blacklist ? 1 : 0;
> > -}
> > -
> >  static bool pcie_retrain_link(struct pcie_link_state *link)
> >  {
> >       struct pci_dev *parent = link->pdev;
> > @@ -952,8 +946,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
> >        */
> >       pcie_aspm_cap_init(link, blacklist);
> >
> > -     /* Setup initial Clock PM state */
> > -     pcie_clkpm_cap_init(link, blacklist);
> > +     link->pm_disabled = blacklist;
> >
> >       /*
> >        * At this stage drivers haven't had an opportunity to change the
> > @@ -1129,8 +1122,8 @@ static int __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
> >       pcie_config_aspm_link(link, policy_to_aspm_state(link));
> >
> >       if (state & PCIE_LINK_STATE_CLKPM)
> > -             link->clkpm_disable = 1;
> > -     pcie_set_clkpm(link, policy_to_clkpm_state(link));
> > +             pcie_set_clkpm(link, 0);
> > +
> >       mutex_unlock(&aspm_lock);
> >       if (sem)
> >               up_read(&pci_bus_sem);
> > @@ -1301,7 +1294,6 @@ static ssize_t clkpm_store(struct device *dev,
> >       down_read(&pci_bus_sem);
> >       mutex_lock(&aspm_lock);
> >
> > -     link->clkpm_disable = !state_enable;
>
> Something is seriously wrong here because clkpm_store() no longer does
> anything with "state_enable", the value we got from the user.
>
> >       pcie_set_clkpm(link, policy_to_clkpm_state(link));
> >
> >       mutex_unlock(&aspm_lock);
> > --
> > 2.20.1
> >
diff mbox series

Patch

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 368828cd427d..e6ae00daa7ae 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -60,8 +60,7 @@  struct pcie_link_state {
 	u32 aspm_default:7;		/* Default ASPM state by BIOS */
 	u32 aspm_disable:7;		/* Disabled ASPM state */
 
-	/* Clock PM state */
-	u32 clkpm_disable:1;		/* Clock PM disabled */
+	u32 pm_disabled:1;		/* Disabled AS and Clock PM ? */
 
 	/* Exit latencies */
 	struct aspm_latency latency_up;	/* Upstream direction exit latency */
@@ -198,7 +197,7 @@  static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
 	 * Don't enable Clock PM if the link is not Clock PM capable
 	 * or Clock PM is disabled
 	 */
-	if (!capable || link->clkpm_disable)
+	if (enable && (!capable || link->pm_disabled))
 		enable = 0;
 	/* Need nothing if the specified equals to current state */
 	if (pcie_get_clkpm_state(link->pdev) == enable)
@@ -206,11 +205,6 @@  static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
 	pcie_set_clkpm_nocheck(link, enable);
 }
 
-static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
-{
-	link->clkpm_disable = blacklist ? 1 : 0;
-}
-
 static bool pcie_retrain_link(struct pcie_link_state *link)
 {
 	struct pci_dev *parent = link->pdev;
@@ -952,8 +946,7 @@  void pcie_aspm_init_link_state(struct pci_dev *pdev)
 	 */
 	pcie_aspm_cap_init(link, blacklist);
 
-	/* Setup initial Clock PM state */
-	pcie_clkpm_cap_init(link, blacklist);
+	link->pm_disabled = blacklist;
 
 	/*
 	 * At this stage drivers haven't had an opportunity to change the
@@ -1129,8 +1122,8 @@  static int __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
 	pcie_config_aspm_link(link, policy_to_aspm_state(link));
 
 	if (state & PCIE_LINK_STATE_CLKPM)
-		link->clkpm_disable = 1;
-	pcie_set_clkpm(link, policy_to_clkpm_state(link));
+		pcie_set_clkpm(link, 0);
+
 	mutex_unlock(&aspm_lock);
 	if (sem)
 		up_read(&pci_bus_sem);
@@ -1301,7 +1294,6 @@  static ssize_t clkpm_store(struct device *dev,
 	down_read(&pci_bus_sem);
 	mutex_lock(&aspm_lock);
 
-	link->clkpm_disable = !state_enable;
 	pcie_set_clkpm(link, policy_to_clkpm_state(link));
 
 	mutex_unlock(&aspm_lock);