[PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[RDH]

This patch avoids unnecessary PCIe link retraining sequences within
the PCIe ASPM common clock setup code by issuing a link retrain
command only if we are actually changing the PCIe clock configuration.

Signed-off-by: Robert D. Houk <rdh@East.Sun.COM>
---
 aspm.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
--- a/drivers/pci/pcie/aspm.c	2009-10-15 20:41:50.000000000 -0400
+++ b/drivers/pci/pcie/aspm.c	2009-11-02 14:29:35.000000000 -0500
@@ -183,6 +183,7 @@ static void pcie_aspm_configure_common_c
 {
 	int ppos, cpos, same_clock = 1;
 	u16 reg16, parent_reg, child_reg[8];
+	u16 lnkctl_ccc_or, lnkctl_ccc_and;
 	unsigned long start_jiffies;
 	struct pci_dev *child, *parent = link->pdev;
 	struct pci_bus *linkbus = parent->subordinate;
@@ -205,6 +206,25 @@ static void pcie_aspm_configure_common_c
 	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
 		same_clock = 0;
 
+	/* Check upstream component for Common Clock Config */
+	pci_read_config_word(parent, ppos + PCI_EXP_LNKCTL, &reg16);
+	lnkctl_ccc_and = lnkctl_ccc_or = (reg16 & PCI_EXP_LNKCTL_CCC);
+
+	/* Scan downstream component for CCC, all functions */
+	list_for_each_entry(child, &linkbus->devices, bus_list) {
+		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);
+		pci_read_config_word(child, cpos + PCI_EXP_LNKCTL, &reg16);
+		lnkctl_ccc_and &= (reg16 & PCI_EXP_LNKCTL_CCC);
+		lnkctl_ccc_or |= (reg16 & PCI_EXP_LNKCTL_CCC);
+	}
+
+	/* If we want Common Clock OFF and no device/function has it on */
+	/* or we want Common Clock ON and every device/function has it on */
+	/* then there is no need to retrain PCIe links */
+	if (((same_clock == 0) && (lnkctl_ccc_or == 0))
+            || ((same_clock == 1) && (lnkctl_ccc_and == PCI_EXP_LNKCTL_CCC)))
+		return;		/* Don't retrain link(s) */
+
 	/* Configure downstream component, all functions */
 	list_for_each_entry(child, &linkbus->devices, bus_list) {
 		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Jesse Barnes]

[Cc'ing linux-pci@vger.kernel.org too]

On Tue, 3 Nov 2009 16:38:20 -0500
RDH <rdh@east.sun.com> wrote:

> 
> This patch avoids unnecessary PCIe link retraining sequences within
> the PCIe ASPM common clock setup code by issuing a link retrain
> command only if we are actually changing the PCIe clock configuration.
> 
> Signed-off-by: Robert D. Houk <rdh@East.Sun.COM>
> ---
>  aspm.c |   20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> --- a/drivers/pci/pcie/aspm.c	2009-10-15 20:41:50.000000000
> -0400 +++ b/drivers/pci/pcie/aspm.c	2009-11-02
> 14:29:35.000000000 -0500 @@ -183,6 +183,7 @@ static void
> pcie_aspm_configure_common_c {
>  	int ppos, cpos, same_clock = 1;
>  	u16 reg16, parent_reg, child_reg[8];
> +	u16 lnkctl_ccc_or, lnkctl_ccc_and;
>  	unsigned long start_jiffies;
>  	struct pci_dev *child, *parent = link->pdev;
>  	struct pci_bus *linkbus = parent->subordinate;
> @@ -205,6 +206,25 @@ static void pcie_aspm_configure_common_c
>  	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
>  		same_clock = 0;
>  
> +	/* Check upstream component for Common Clock Config */
> +	pci_read_config_word(parent, ppos + PCI_EXP_LNKCTL, &reg16);
> +	lnkctl_ccc_and = lnkctl_ccc_or = (reg16 &
> PCI_EXP_LNKCTL_CCC); +
> +	/* Scan downstream component for CCC, all functions */
> +	list_for_each_entry(child, &linkbus->devices, bus_list) {
> +		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);
> +		pci_read_config_word(child, cpos + PCI_EXP_LNKCTL,
> &reg16);
> +		lnkctl_ccc_and &= (reg16 & PCI_EXP_LNKCTL_CCC);
> +		lnkctl_ccc_or |= (reg16 & PCI_EXP_LNKCTL_CCC);
> +	}
> +
> +	/* If we want Common Clock OFF and no device/function has it
> on */
> +	/* or we want Common Clock ON and every device/function has
> it on */
> +	/* then there is no need to retrain PCIe links */
> +	if (((same_clock == 0) && (lnkctl_ccc_or == 0))
> +            || ((same_clock == 1) && (lnkctl_ccc_and ==
> PCI_EXP_LNKCTL_CCC)))
> +		return;		/* Don't retrain link(s) */
> +
>  	/* Configure downstream component, all functions */
>  	list_for_each_entry(child, &linkbus->devices, bus_list) {
>  		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);
> 

Seems ok to me, anyone have comments?

-- 
Jesse Barnes, Intel Open Source Technology Center

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Bjorn Helgaas]

On Wednesday 04 November 2009 12:03:21 pm Jesse Barnes wrote:
> [Cc'ing linux-pci@vger.kernel.org too]
> 
> On Tue, 3 Nov 2009 16:38:20 -0500
> RDH <rdh@east.sun.com> wrote:
> 
> > 
> > This patch avoids unnecessary PCIe link retraining sequences within
> > the PCIe ASPM common clock setup code by issuing a link retrain
> > command only if we are actually changing the PCIe clock configuration.
> > 
> > Signed-off-by: Robert D. Houk <rdh@East.Sun.COM>
> > ---
> >  aspm.c |   20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> > --- a/drivers/pci/pcie/aspm.c	2009-10-15 20:41:50.000000000
> > -0400 +++ b/drivers/pci/pcie/aspm.c	2009-11-02
> > 14:29:35.000000000 -0500 @@ -183,6 +183,7 @@ static void
> > pcie_aspm_configure_common_c {
> >  	int ppos, cpos, same_clock = 1;
> >  	u16 reg16, parent_reg, child_reg[8];
> > +	u16 lnkctl_ccc_or, lnkctl_ccc_and;
> >  	unsigned long start_jiffies;
> >  	struct pci_dev *child, *parent = link->pdev;
> >  	struct pci_bus *linkbus = parent->subordinate;
> > @@ -205,6 +206,25 @@ static void pcie_aspm_configure_common_c
> >  	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
> >  		same_clock = 0;
> >  
> > +	/* Check upstream component for Common Clock Config */
> > +	pci_read_config_word(parent, ppos + PCI_EXP_LNKCTL, &reg16);
> > +	lnkctl_ccc_and = lnkctl_ccc_or = (reg16 &
> > PCI_EXP_LNKCTL_CCC); +
> > +	/* Scan downstream component for CCC, all functions */
> > +	list_for_each_entry(child, &linkbus->devices, bus_list) {
> > +		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);

Some other places in pcie/aspm (e.g., pcie_set_clkpm_nocheck() and
pcie_clkpm_cap_init()) check cpos for NULL.  Your code looks
superficially similar, so maybe you should check it, too, although
I do see many other place in aspm where we *don't* check it.

We look up this capability so often, I wonder if we should save it
in the struct pci_dev or struct pcie_link or something in such a
way that if we have a struct pcie_link, we are guaranteed that there
is a PCIe capability, and we don't have to search for it again.

Bjorn

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Kenji Kaneshige]

Bjorn Helgaas wrote:
> On Wednesday 04 November 2009 12:03:21 pm Jesse Barnes wrote:
>> [Cc'ing linux-pci@vger.kernel.org too]
>>
>> On Tue, 3 Nov 2009 16:38:20 -0500
>> RDH <rdh@east.sun.com> wrote:
>>
>>> This patch avoids unnecessary PCIe link retraining sequences within
>>> the PCIe ASPM common clock setup code by issuing a link retrain
>>> command only if we are actually changing the PCIe clock configuration.
>>>
>>> Signed-off-by: Robert D. Houk <rdh@East.Sun.COM>
>>> ---
>>>  aspm.c |   20 ++++++++++++++++++++
>>>  1 file changed, 20 insertions(+)
>>> --- a/drivers/pci/pcie/aspm.c	2009-10-15 20:41:50.000000000
>>> -0400 +++ b/drivers/pci/pcie/aspm.c	2009-11-02
>>> 14:29:35.000000000 -0500 @@ -183,6 +183,7 @@ static void
>>> pcie_aspm_configure_common_c {
>>>  	int ppos, cpos, same_clock = 1;
>>>  	u16 reg16, parent_reg, child_reg[8];
>>> +	u16 lnkctl_ccc_or, lnkctl_ccc_and;
>>>  	unsigned long start_jiffies;
>>>  	struct pci_dev *child, *parent = link->pdev;
>>>  	struct pci_bus *linkbus = parent->subordinate;
>>> @@ -205,6 +206,25 @@ static void pcie_aspm_configure_common_c
>>>  	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
>>>  		same_clock = 0;
>>>  
>>> +	/* Check upstream component for Common Clock Config */
>>> +	pci_read_config_word(parent, ppos + PCI_EXP_LNKCTL, &reg16);
>>> +	lnkctl_ccc_and = lnkctl_ccc_or = (reg16 &
>>> PCI_EXP_LNKCTL_CCC); +
>>> +	/* Scan downstream component for CCC, all functions */
>>> +	list_for_each_entry(child, &linkbus->devices, bus_list) {
>>> +		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);
> 
> Some other places in pcie/aspm (e.g., pcie_set_clkpm_nocheck() and
> pcie_clkpm_cap_init()) check cpos for NULL.  Your code looks
> superficially similar, so maybe you should check it, too, although
> I do see many other place in aspm where we *don't* check it.
> 
> We look up this capability so often, I wonder if we should save it
> in the struct pci_dev or struct pcie_link or something in such a
> way that if we have a struct pcie_link, we are guaranteed that there
> is a PCIe capability, and we don't have to search for it again.
> 

I agree. There are a lot of codes using pci_find_capability() to
search PCIe capability offset in addition to ASPM driver. So I
think it's good idea to have PCIe cap offset in struct pci_dev.

To be honest, I have already made a following patch to add a new
field into struct pci_dev and some other patches to use this new
field a few months ago. But I have never posted them yet. If it
is a right direction, I would like to update and post them soon.

Thanks,
Kenji Kaneshige


There are a lot of codes that searches PCI express capability offset
in the PCI configuration space using pci_find_capability(). Caching it
in the struct pci_dev will reduce unncecessary search. This patch adds
an additional 'pcie_cap' fields into struct pci_dev, which is
initialized at pci device scan time (in set_pcie_port_type()).

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>

---
 drivers/pci/probe.c |    1 +
 include/linux/pci.h |    1 +
 2 files changed, 2 insertions(+)

Index: 20090825/drivers/pci/probe.c
===================================================================
--- 20090825.orig/drivers/pci/probe.c
+++ 20090825/drivers/pci/probe.c
@@ -693,6 +693,7 @@ static void set_pcie_port_type(struct pc
 	if (!pos)
 		return;
 	pdev->is_pcie = 1;
+	pdev->pcie_cap = pos;
 	pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, &reg16);
 	pdev->pcie_type = (reg16 & PCI_EXP_FLAGS_TYPE) >> 4;
 }
Index: 20090825/include/linux/pci.h
===================================================================
--- 20090825.orig/include/linux/pci.h
+++ 20090825/include/linux/pci.h
@@ -218,6 +218,7 @@ struct pci_dev {
 	unsigned int	class;		/* 3 bytes: (base,sub,prog-if) */
 	u8		revision;	/* PCI revision, low byte of class word */
 	u8		hdr_type;	/* PCI header type (`multi' flag masked out) */
+	u8		pcie_cap;	/* PCI-E capability offset */
 	u8		pcie_type;	/* PCI-E device/port type */
 	u8		rom_base_reg;	/* which config register controls the ROM */
 	u8		pin;  		/* which interrupt pin this device uses */

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Bjorn Helgaas]

On Wednesday 04 November 2009 08:05:11 pm Kenji Kaneshige wrote:
> Bjorn Helgaas wrote:
> > On Wednesday 04 November 2009 12:03:21 pm Jesse Barnes wrote:
> >> [Cc'ing linux-pci@vger.kernel.org too]
> >>
> >> On Tue, 3 Nov 2009 16:38:20 -0500
> >> RDH <rdh@east.sun.com> wrote:

> >>> +	/* Check upstream component for Common Clock Config */
> >>> +	pci_read_config_word(parent, ppos + PCI_EXP_LNKCTL, &reg16);
> >>> +	lnkctl_ccc_and = lnkctl_ccc_or = (reg16 &
> >>> PCI_EXP_LNKCTL_CCC); +
> >>> +	/* Scan downstream component for CCC, all functions */
> >>> +	list_for_each_entry(child, &linkbus->devices, bus_list) {
> >>> +		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);
> > 
> > Some other places in pcie/aspm (e.g., pcie_set_clkpm_nocheck() and
> > pcie_clkpm_cap_init()) check cpos for NULL.  Your code looks
> > superficially similar, so maybe you should check it, too, although
> > I do see many other place in aspm where we *don't* check it.
> > 
> > We look up this capability so often, I wonder if we should save it
> > in the struct pci_dev or struct pcie_link or something in such a
> > way that if we have a struct pcie_link, we are guaranteed that there
> > is a PCIe capability, and we don't have to search for it again.
> > 
> 
> I agree. There are a lot of codes using pci_find_capability() to
> search PCIe capability offset in addition to ASPM driver. So I
> think it's good idea to have PCIe cap offset in struct pci_dev.
> 
> To be honest, I have already made a following patch to add a new
> field into struct pci_dev and some other patches to use this new
> field a few months ago. But I have never posted them yet. If it
> is a right direction, I would like to update and post them soon.
> 
> Thanks,
> Kenji Kaneshige
> 
> 
> There are a lot of codes that searches PCI express capability offset
> in the PCI configuration space using pci_find_capability(). Caching it
> in the struct pci_dev will reduce unncecessary search. This patch adds
> an additional 'pcie_cap' fields into struct pci_dev, which is
> initialized at pci device scan time (in set_pcie_port_type()).
> 
> Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
> 
> ---
>  drivers/pci/probe.c |    1 +
>  include/linux/pci.h |    1 +
>  2 files changed, 2 insertions(+)
> 
> Index: 20090825/drivers/pci/probe.c
> ===================================================================
> --- 20090825.orig/drivers/pci/probe.c
> +++ 20090825/drivers/pci/probe.c
> @@ -693,6 +693,7 @@ static void set_pcie_port_type(struct pc
>  	if (!pos)
>  		return;
>  	pdev->is_pcie = 1;
> +	pdev->pcie_cap = pos;
>  	pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, &reg16);
>  	pdev->pcie_type = (reg16 & PCI_EXP_FLAGS_TYPE) >> 4;
>  }
> Index: 20090825/include/linux/pci.h
> ===================================================================
> --- 20090825.orig/include/linux/pci.h
> +++ 20090825/include/linux/pci.h
> @@ -218,6 +218,7 @@ struct pci_dev {
>  	unsigned int	class;		/* 3 bytes: (base,sub,prog-if) */
>  	u8		revision;	/* PCI revision, low byte of class word */
>  	u8		hdr_type;	/* PCI header type (`multi' flag masked out) */
> +	u8		pcie_cap;	/* PCI-E capability offset */
>  	u8		pcie_type;	/* PCI-E device/port type */
>  	u8		rom_base_reg;	/* which config register controls the ROM */
>  	u8		pin;  		/* which interrupt pin this device uses */
> 

Here's another possibility, the idea being to collect all the PCIe
stuff in one place.  This would require a lot of changes in the PCIe
driver code, but most of them would be trivial.


diff --git a/include/linux/pci.h b/include/linux/pci.h
index f5c7cd3..29272ab 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -198,6 +198,14 @@ struct pci_vpd;
 struct pci_sriov;
 struct pci_ats;
 
+struct pcie_dev {
+#ifdef CONFIG_PCIEASPM
+	struct pcie_link_state	*link_state;	/* ASPM link state. */
+#endif
+	u8		cap;	/* PCI-E capability offset */
+	u8		type;	/* PCI-E device/port type */
+};
+
 /*
  * The pci_dev structure is used to describe PCI devices.
  */
@@ -218,7 +226,6 @@ struct pci_dev {
 	unsigned int	class;		/* 3 bytes: (base,sub,prog-if) */
 	u8		revision;	/* PCI revision, low byte of class word */
 	u8		hdr_type;	/* PCI header type (`multi' flag masked out) */
-	u8		pcie_type;	/* PCI-E device/port type */
 	u8		rom_base_reg;	/* which config register controls the ROM */
 	u8		pin;  		/* which interrupt pin this device uses */
 
@@ -243,10 +250,6 @@ struct pci_dev {
 	unsigned int	no_d1d2:1;	/* Only allow D0 and D3 */
 	unsigned int	wakeup_prepared:1;
 
-#ifdef CONFIG_PCIEASPM
-	struct pcie_link_state	*link_state;	/* ASPM link state. */
-#endif
-
 	pci_channel_state_t error_state;	/* current connectivity state */
 	struct	device	dev;		/* Generic device interface */
 
@@ -273,7 +276,6 @@ struct pci_dev {
 	unsigned int	msix_enabled:1;
 	unsigned int	ari_enabled:1;	/* ARI forwarding */
 	unsigned int	is_managed:1;
-	unsigned int	is_pcie:1;
 	unsigned int    needs_freset:1; /* Dev requires fundamental reset */
 	unsigned int	state_saved:1;
 	unsigned int	is_physfn:1;
@@ -293,6 +295,7 @@ struct pci_dev {
 	struct list_head msi_list;
 #endif
 	struct pci_vpd *vpd;
+	struct pci_pcie *pcie;
 #ifdef CONFIG_PCI_IOV
 	union {
 		struct pci_sriov *sriov;	/* SR-IOV capability related */
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 5c4ce1b..f85f2e7 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -684,13 +684,21 @@ static void set_pcie_port_type(struct pci_dev *pdev)
 {
 	int pos;
 	u16 reg16;
+	struct pcie_dev *pcie;
 
 	pos = pci_find_capability(pdev, PCI_CAP_ID_EXP);
 	if (!pos)
 		return;
-	pdev->is_pcie = 1;
+
+	pcie = kzalloc(sizeof(struct pci_dev), GFP_KERNEL);
+	if (!pcie)
+		return;
+
 	pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, &reg16);
-	pdev->pcie_type = (reg16 & PCI_EXP_FLAGS_TYPE) >> 4;
+
+	pcie->type = (reg16 & PCI_EXP_FLAGS_TYPE) >> 4;
+	pcie->cap = pos;
+	pdev->pcie = pcie;
 }
 
 static void set_pcie_hotplug_bridge(struct pci_dev *pdev)

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Matthew Wilcox]

On Thu, Nov 05, 2009 at 12:59:25PM -0600, Bjorn Helgaas wrote:
> Here's another possibility, the idea being to collect all the PCIe
> stuff in one place.  This would require a lot of changes in the PCIe
> driver code, but most of them would be trivial.

I don't like the idea of kmallocing a 6- or 10-byte data structure
... better to keep it in the pci_dev.  Maybe embedding a pcie_dev inside
the pci_dev would be a good idea, but unless there're more things to
move to it, this seems like a net loss to me.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Bjorn Helgaas]

On Thursday 05 November 2009 12:07:07 pm Matthew Wilcox wrote:
> On Thu, Nov 05, 2009 at 12:59:25PM -0600, Bjorn Helgaas wrote:
> > Here's another possibility, the idea being to collect all the PCIe
> > stuff in one place.  This would require a lot of changes in the PCIe
> > driver code, but most of them would be trivial.
> 
> I don't like the idea of kmallocing a 6- or 10-byte data structure
> ... better to keep it in the pci_dev.  Maybe embedding a pcie_dev inside
> the pci_dev would be a good idea, but unless there're more things to
> move to it, this seems like a net loss to me.

That's true, it's not worth it for such a small structure.  I figured
there would probably be more PCIe-related stuff that could go there,
e.g., embedding the link_state directly.  But I haven't looked to
see whether there actually is enough PCIe stuff to make it worthwhile.

Bjorn

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Kenji Kaneshige]

Bjorn Helgaas wrote:
> On Thursday 05 November 2009 12:07:07 pm Matthew Wilcox wrote:
>> On Thu, Nov 05, 2009 at 12:59:25PM -0600, Bjorn Helgaas wrote:
>>> Here's another possibility, the idea being to collect all the PCIe
>>> stuff in one place.  This would require a lot of changes in the PCIe
>>> driver code, but most of them would be trivial.
>> I don't like the idea of kmallocing a 6- or 10-byte data structure
>> ... better to keep it in the pci_dev.  Maybe embedding a pcie_dev inside
>> the pci_dev would be a good idea, but unless there're more things to
>> move to it, this seems like a net loss to me.
> 
> That's true, it's not worth it for such a small structure.  I figured
> there would probably be more PCIe-related stuff that could go there,
> e.g., embedding the link_state directly.  But I haven't looked to
> see whether there actually is enough PCIe stuff to make it worthwhile.
> 

In my understanding, there are the following PCIe specific data in
struct pci_dev. It is not many.

	u8 pcie_cap;			*I added this time
	u8 pcie_type;
	struct pcie_link_state *link_state;
	unsigned int ari_enabled:1;
	unsigned int is_pcie:1;		*No longer needed and will be removed.
	unsigned int aer_firmware_first:1;

How about keeping cap offset in pci_dev so far and introducing the
following wrapper function?

static inline pcie_cap(struct pci_dev *pdev)
{
        return pdev->pcie_cap;
}

When we actually need a new data structure for PCIe-related stuff in the
future, all we need to do would be changing this wrapper like below.

static inline pcie_cap(struct pci_dev *pdev)
{
	struct pcie_dev *pcie = pdev->pcie;
	if (pcie)
		return pcie->cap;
	return 0;
}

Thanks,
Kenji Kaneshige

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Matthew Wilcox]

On Thu, Nov 05, 2009 at 12:05:11PM +0900, Kenji Kaneshige wrote:
> There are a lot of codes that searches PCI express capability offset
> in the PCI configuration space using pci_find_capability(). Caching it
> in the struct pci_dev will reduce unncecessary search. This patch adds
> an additional 'pcie_cap' fields into struct pci_dev, which is
> initialized at pci device scan time (in set_pcie_port_type()).

I think adding this should imply the removal of ->is_pcie.  pcie_cap == 0
means !is_pcie.

> Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
> 
> ---
>  drivers/pci/probe.c |    1 +
>  include/linux/pci.h |    1 +
>  2 files changed, 2 insertions(+)
> 
> Index: 20090825/drivers/pci/probe.c
> ===================================================================
> --- 20090825.orig/drivers/pci/probe.c
> +++ 20090825/drivers/pci/probe.c
> @@ -693,6 +693,7 @@ static void set_pcie_port_type(struct pc
>  	if (!pos)
>  		return;
>  	pdev->is_pcie = 1;
> +	pdev->pcie_cap = pos;
>  	pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, &reg16);
>  	pdev->pcie_type = (reg16 & PCI_EXP_FLAGS_TYPE) >> 4;
>  }
> Index: 20090825/include/linux/pci.h
> ===================================================================
> --- 20090825.orig/include/linux/pci.h
> +++ 20090825/include/linux/pci.h
> @@ -218,6 +218,7 @@ struct pci_dev {
>  	unsigned int	class;		/* 3 bytes: (base,sub,prog-if) */
>  	u8		revision;	/* PCI revision, low byte of class word */
>  	u8		hdr_type;	/* PCI header type (`multi' flag masked out) */
> +	u8		pcie_cap;	/* PCI-E capability offset */
>  	u8		pcie_type;	/* PCI-E device/port type */
>  	u8		rom_base_reg;	/* which config register controls the ROM */
>  	u8		pin;  		/* which interrupt pin this device uses */
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Kenji Kaneshige]

Matthew Wilcox wrote:
> On Thu, Nov 05, 2009 at 12:05:11PM +0900, Kenji Kaneshige wrote:
>> There are a lot of codes that searches PCI express capability offset
>> in the PCI configuration space using pci_find_capability(). Caching it
>> in the struct pci_dev will reduce unncecessary search. This patch adds
>> an additional 'pcie_cap' fields into struct pci_dev, which is
>> initialized at pci device scan time (in set_pcie_port_type()).
> 
> I think adding this should imply the removal of ->is_pcie.  pcie_cap == 0
> means !is_pcie.

Right.

But, as you know, we need to change users of is_pcie (including some
adapter card drivers) before removing it.

Thanks,
Kenji Kaneshige

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Jesse Barnes]

On Thu, 05 Nov 2009 12:05:11 +0900
Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com> wrote:
> 
> There are a lot of codes that searches PCI express capability offset
> in the PCI configuration space using pci_find_capability(). Caching it
> in the struct pci_dev will reduce unncecessary search. This patch adds
> an additional 'pcie_cap' fields into struct pci_dev, which is
> initialized at pci device scan time (in set_pcie_port_type()).
> 
> Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
> 
> ---
>  drivers/pci/probe.c |    1 +
>  include/linux/pci.h |    1 +
>  2 files changed, 2 insertions(+)
> 
> Index: 20090825/drivers/pci/probe.c
> ===================================================================
> --- 20090825.orig/drivers/pci/probe.c
> +++ 20090825/drivers/pci/probe.c
> @@ -693,6 +693,7 @@ static void set_pcie_port_type(struct pc
>  	if (!pos)
>  		return;
>  	pdev->is_pcie = 1;
> +	pdev->pcie_cap = pos;
>  	pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, &reg16);
>  	pdev->pcie_type = (reg16 & PCI_EXP_FLAGS_TYPE) >> 4;
>  }
> Index: 20090825/include/linux/pci.h
> ===================================================================
> --- 20090825.orig/include/linux/pci.h
> +++ 20090825/include/linux/pci.h
> @@ -218,6 +218,7 @@ struct pci_dev {
>  	unsigned int	class;		/* 3 bytes:
> (base,sub,prog-if) */ u8		revision;	/* PCI
> revision, low byte of class word */ u8
> hdr_type;	/* PCI header type (`multi' flag masked out) */
> +	u8		pcie_cap;	/* PCI-E capability
> offset */ u8		pcie_type;	/* PCI-E device/port
> type */ u8		rom_base_reg;	/* which config
> register controls the ROM */ u8		pin;
> 		/* which interrupt pin this device uses */
> 
> 

Applied this one to linux-next, thanks Kenji-san.

-- 
Jesse Barnes, Intel Open Source Technology Center

Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

[Kenji Kaneshige]

Jesse Barnes wrote:
> [Cc'ing linux-pci@vger.kernel.org too]
> 
> On Tue, 3 Nov 2009 16:38:20 -0500
> RDH <rdh@east.sun.com> wrote:
> 
>> This patch avoids unnecessary PCIe link retraining sequences within
>> the PCIe ASPM common clock setup code by issuing a link retrain
>> command only if we are actually changing the PCIe clock configuration.
>>
>> Signed-off-by: Robert D. Houk <rdh@East.Sun.COM>
>> ---
>>  aspm.c |   20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>> --- a/drivers/pci/pcie/aspm.c	2009-10-15 20:41:50.000000000
>> -0400 +++ b/drivers/pci/pcie/aspm.c	2009-11-02
>> 14:29:35.000000000 -0500 @@ -183,6 +183,7 @@ static void
>> pcie_aspm_configure_common_c {
>>  	int ppos, cpos, same_clock = 1;
>>  	u16 reg16, parent_reg, child_reg[8];
>> +	u16 lnkctl_ccc_or, lnkctl_ccc_and;
>>  	unsigned long start_jiffies;
>>  	struct pci_dev *child, *parent = link->pdev;
>>  	struct pci_bus *linkbus = parent->subordinate;
>> @@ -205,6 +206,25 @@ static void pcie_aspm_configure_common_c
>>  	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
>>  		same_clock = 0;
>>  
>> +	/* Check upstream component for Common Clock Config */
>> +	pci_read_config_word(parent, ppos + PCI_EXP_LNKCTL, &reg16);
>> +	lnkctl_ccc_and = lnkctl_ccc_or = (reg16 &
>> PCI_EXP_LNKCTL_CCC); +
>> +	/* Scan downstream component for CCC, all functions */
>> +	list_for_each_entry(child, &linkbus->devices, bus_list) {
>> +		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);
>> +		pci_read_config_word(child, cpos + PCI_EXP_LNKCTL,
>> &reg16);
>> +		lnkctl_ccc_and &= (reg16 & PCI_EXP_LNKCTL_CCC);
>> +		lnkctl_ccc_or |= (reg16 & PCI_EXP_LNKCTL_CCC);
>> +	}
>> +
>> +	/* If we want Common Clock OFF and no device/function has it
>> on */
>> +	/* or we want Common Clock ON and every device/function has
>> it on */
>> +	/* then there is no need to retrain PCIe links */
>> +	if (((same_clock == 0) && (lnkctl_ccc_or == 0))
>> +            || ((same_clock == 1) && (lnkctl_ccc_and ==
>> PCI_EXP_LNKCTL_CCC)))
>> +		return;		/* Don't retrain link(s) */
>> +
>>  	/* Configure downstream component, all functions */
>>  	list_for_each_entry(child, &linkbus->devices, bus_list) {
>>  		cpos = pci_find_capability(child, PCI_CAP_ID_EXP);
>>
> 
> Seems ok to me, anyone have comments?
> 

Hi Robert,

How about like below? IMHO, it is easier to understand.
(Please note that I don't test it yet)

Thanks,
Kenji Kaneshige


---
 drivers/pci/pcie/aspm.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

Index: 20091026/drivers/pci/pcie/aspm.c
===================================================================
--- 20091026.orig/drivers/pci/pcie/aspm.c
+++ 20091026/drivers/pci/pcie/aspm.c
@@ -186,6 +186,7 @@ static void pcie_aspm_configure_common_c
 	unsigned long start_jiffies;
 	struct pci_dev *child, *parent = link->pdev;
 	struct pci_bus *linkbus = parent->subordinate;
+	bool ccc_updated = false;
 	/*
 	 * All functions of a slot should have the same Slot Clock
 	 * Configuration, so just check one function
@@ -214,7 +215,10 @@ static void pcie_aspm_configure_common_c
 			reg16 |= PCI_EXP_LNKCTL_CCC;
 		else
 			reg16 &= ~PCI_EXP_LNKCTL_CCC;
+		if (reg16 == child_reg[PCI_FUNC(child->devfn)])
+			continue;
 		pci_write_config_word(child, cpos + PCI_EXP_LNKCTL, reg16);
+		ccc_updated = true;
 	}
 
 	/* Configure upstream component */
@@ -224,7 +228,14 @@ static void pcie_aspm_configure_common_c
 		reg16 |= PCI_EXP_LNKCTL_CCC;
 	else
 		reg16 &= ~PCI_EXP_LNKCTL_CCC;
-	pci_write_config_word(parent, ppos + PCI_EXP_LNKCTL, reg16);
+	if (reg16 != parent_reg) {
+		pci_write_config_word(parent, ppos + PCI_EXP_LNKCTL, reg16);
+		ccc_updated = true;
+	}
+
+	/* Don't need to retrain link if there is no change in CCC */
+	if (!ccc_updated)
+		return;
 
 	/* Retrain link */
 	reg16 |= PCI_EXP_LNKCTL_RL;