Re: [v3] PCI: Avoid unsync of LTR mechanism configuration

2021-02-03 Thread Mika Westerberg 
On Wed, Feb 03, 2021 at 10:14:01AM +0800, Mingchuang Qiao wrote:
> Hi,
> 
> On Mon, 2021-02-01 at 13:32 +0200, Mika Westerberg wrote:
> > Hi,
> > 
> > On Fri, Jan 29, 2021 at 03:11:37PM +0800, mingchuang.q...@mediatek.com 
> > wrote:
> > > From: Mingchuang Qiao 
> > > 
> > > In bus scan flow, the "LTR Mechanism Enable" bit of DEVCTL2 register is
> > > configured in pci_configure_ltr(). If device and bridge both support LTR
> > > mechanism, the "LTR Mechanism Enable" bit of device and bridge will be
> > > enabled in DEVCTL2 register. And pci_dev->ltr_path will be set as 1.
> > > 
> > > If PCIe link goes down when device resets, the "LTR Mechanism Enable" bit
> > > of bridge will change to 0 according to PCIe r5.0, sec 7.5.3.16. However,
> > > the pci_dev->ltr_path value of bridge is still 1.
> > > 
> > > For following conditions, check and re-configure "LTR Mechanism Enable" 
> > > bit
> > > of bridge to make "LTR Mechanism Enable" bit mtach ltr_path value.
> > 
> > Typo mtach -> match.
> > 
> > >-before configuring device's LTR for hot-remove/hot-add
> > >-before restoring device's DEVCTL2 register when restore device state
> > > 
> > > Signed-off-by: Mingchuang Qiao 
> > > ---
> > > changes of v2
> > >  -modify patch description
> > >  -reconfigure bridge's LTR before restoring device DEVCTL2 register
> > > changes of v3
> > >  -call pci_reconfigure_bridge_ltr() in probe.c
> > 
> > Hmm, which part of this patch takes care of the reset path? It is not
> > entirely clear to me at least.
> > 
> 
> When device resets and link goes down, there seems to have two methods
> to recover for software. 
>-One is that trigger device removal and rescan.
>-The other is that restore device with pci_restore_state() after link
> comes back up.
> For above both scenarios, we need check and reconfigure "LTR Mechanism
> Enable" bit of bridge. It's also this patch intends to do.
>-For the rescan scenario, it's done in pci_configure_ltr().
>-For the restore scenario, it's done in pci_restore_pcie_state().

Okay, thanks for the clarification!

Re: [v3] PCI: Avoid unsync of LTR mechanism configuration

2021-02-02 Thread Mingchuang Qiao 
Hi,

On Mon, 2021-02-01 at 13:32 +0200, Mika Westerberg wrote:
> Hi,
> 
> On Fri, Jan 29, 2021 at 03:11:37PM +0800, mingchuang.q...@mediatek.com wrote:
> > From: Mingchuang Qiao 
> > 
> > In bus scan flow, the "LTR Mechanism Enable" bit of DEVCTL2 register is
> > configured in pci_configure_ltr(). If device and bridge both support LTR
> > mechanism, the "LTR Mechanism Enable" bit of device and bridge will be
> > enabled in DEVCTL2 register. And pci_dev->ltr_path will be set as 1.
> > 
> > If PCIe link goes down when device resets, the "LTR Mechanism Enable" bit
> > of bridge will change to 0 according to PCIe r5.0, sec 7.5.3.16. However,
> > the pci_dev->ltr_path value of bridge is still 1.
> > 
> > For following conditions, check and re-configure "LTR Mechanism Enable" bit
> > of bridge to make "LTR Mechanism Enable" bit mtach ltr_path value.
> 
> Typo mtach -> match.
> 
> >-before configuring device's LTR for hot-remove/hot-add
> >-before restoring device's DEVCTL2 register when restore device state
> > 
> > Signed-off-by: Mingchuang Qiao 
> > ---
> > changes of v2
> >  -modify patch description
> >  -reconfigure bridge's LTR before restoring device DEVCTL2 register
> > changes of v3
> >  -call pci_reconfigure_bridge_ltr() in probe.c
> 
> Hmm, which part of this patch takes care of the reset path? It is not
> entirely clear to me at least.
> 

When device resets and link goes down, there seems to have two methods
to recover for software. 
   -One is that trigger device removal and rescan.
   -The other is that restore device with pci_restore_state() after link
comes back up.
For above both scenarios, we need check and reconfigure "LTR Mechanism
Enable" bit of bridge. It's also this patch intends to do.
   -For the rescan scenario, it's done in pci_configure_ltr().
   -For the restore scenario, it's done in pci_restore_pcie_state().

> > ---
> >  drivers/pci/pci.c   | 25 +
> >  drivers/pci/pci.h   |  1 +
> >  drivers/pci/probe.c | 13 ++---
> >  3 files changed, 36 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index b9fecc25d213..12b557c8f062 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -1437,6 +1437,24 @@ static int pci_save_pcie_state(struct pci_dev *dev)
> > return 0;
> >  }
> >  
> > +void pci_reconfigure_bridge_ltr(struct pci_dev *dev)
> > +{
> > +#ifdef CONFIG_PCIEASPM
> > +   struct pci_dev *bridge;
> > +   u32 ctl;
> > +
> > +   bridge = pci_upstream_bridge(dev);
> > +   if (bridge && bridge->ltr_path) {
> > +   pcie_capability_read_dword(bridge, PCI_EXP_DEVCTL2, );
> > +   if (!(ctl & PCI_EXP_DEVCTL2_LTR_EN)) {
> > +   pci_dbg(bridge, "re-enabling LTR\n");
> > +   pcie_capability_set_word(bridge, PCI_EXP_DEVCTL2,
> > +PCI_EXP_DEVCTL2_LTR_EN);
> > +   }
> > +   }
> > +#endif
> > +}
> > +
> >  static void pci_restore_pcie_state(struct pci_dev *dev)
> >  {
> > int i = 0;
> > @@ -1447,6 +1465,13 @@ static void pci_restore_pcie_state(struct pci_dev 
> > *dev)
> > if (!save_state)
> > return;
> >  
> > +   /*
> > +* Downstream ports reset the LTR enable bit when link goes down.
> > +* Check and re-configure the bit here before restoring device.
> > +* PCIe r5.0, sec 7.5.3.16.
> > +*/
> > +   pci_reconfigure_bridge_ltr(dev);
> > +
> > cap = (u16 *)_state->cap.data[0];
> > pcie_capability_write_word(dev, PCI_EXP_DEVCTL, cap[i++]);
> > pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]);
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index 5c59365092fa..a660a01358c5 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -111,6 +111,7 @@ void pci_free_cap_save_buffers(struct pci_dev *dev);
> >  bool pci_bridge_d3_possible(struct pci_dev *dev);
> >  void pci_bridge_d3_update(struct pci_dev *dev);
> >  void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev);
> > +void pci_reconfigure_bridge_ltr(struct pci_dev *dev);
> 
> Nit: calling it pci_bridge_reconfigure_ltr() would match better with the
> other function names.
> 

Thanks for the suggestion. I will update the name in next patch :)

> >  
> >  static inline void pci_wakeup_event(struct pci_dev *dev)
> >  {
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index 953f15abc850..fa6075093f3b 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -2132,9 +2132,16 @@ static void pci_configure_ltr(struct pci_dev *dev)
> >  * Complex and all intermediate Switches indicate support for LTR.
> >  * PCIe r4.0, sec 6.18.
> >  */
> > -   if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
> > -   ((bridge = pci_upstream_bridge(dev)) &&
> > - bridge->ltr_path)) {
> > +   if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) {
> > +   pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,
> > +

Re: [v3] PCI: Avoid unsync of LTR mechanism configuration

2021-02-01 Thread Mika Westerberg 
Hi,

On Fri, Jan 29, 2021 at 03:11:37PM +0800, mingchuang.q...@mediatek.com wrote:
> From: Mingchuang Qiao 
> 
> In bus scan flow, the "LTR Mechanism Enable" bit of DEVCTL2 register is
> configured in pci_configure_ltr(). If device and bridge both support LTR
> mechanism, the "LTR Mechanism Enable" bit of device and bridge will be
> enabled in DEVCTL2 register. And pci_dev->ltr_path will be set as 1.
> 
> If PCIe link goes down when device resets, the "LTR Mechanism Enable" bit
> of bridge will change to 0 according to PCIe r5.0, sec 7.5.3.16. However,
> the pci_dev->ltr_path value of bridge is still 1.
> 
> For following conditions, check and re-configure "LTR Mechanism Enable" bit
> of bridge to make "LTR Mechanism Enable" bit mtach ltr_path value.

Typo mtach -> match.

>-before configuring device's LTR for hot-remove/hot-add
>-before restoring device's DEVCTL2 register when restore device state
> 
> Signed-off-by: Mingchuang Qiao 
> ---
> changes of v2
>  -modify patch description
>  -reconfigure bridge's LTR before restoring device DEVCTL2 register
> changes of v3
>  -call pci_reconfigure_bridge_ltr() in probe.c

Hmm, which part of this patch takes care of the reset path? It is not
entirely clear to me at least.

> ---
>  drivers/pci/pci.c   | 25 +
>  drivers/pci/pci.h   |  1 +
>  drivers/pci/probe.c | 13 ++---
>  3 files changed, 36 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b9fecc25d213..12b557c8f062 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1437,6 +1437,24 @@ static int pci_save_pcie_state(struct pci_dev *dev)
>   return 0;
>  }
>  
> +void pci_reconfigure_bridge_ltr(struct pci_dev *dev)
> +{
> +#ifdef CONFIG_PCIEASPM
> + struct pci_dev *bridge;
> + u32 ctl;
> +
> + bridge = pci_upstream_bridge(dev);
> + if (bridge && bridge->ltr_path) {
> + pcie_capability_read_dword(bridge, PCI_EXP_DEVCTL2, );
> + if (!(ctl & PCI_EXP_DEVCTL2_LTR_EN)) {
> + pci_dbg(bridge, "re-enabling LTR\n");
> + pcie_capability_set_word(bridge, PCI_EXP_DEVCTL2,
> +  PCI_EXP_DEVCTL2_LTR_EN);
> + }
> + }
> +#endif
> +}
> +
>  static void pci_restore_pcie_state(struct pci_dev *dev)
>  {
>   int i = 0;
> @@ -1447,6 +1465,13 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
>   if (!save_state)
>   return;
>  
> + /*
> +  * Downstream ports reset the LTR enable bit when link goes down.
> +  * Check and re-configure the bit here before restoring device.
> +  * PCIe r5.0, sec 7.5.3.16.
> +  */
> + pci_reconfigure_bridge_ltr(dev);
> +
>   cap = (u16 *)_state->cap.data[0];
>   pcie_capability_write_word(dev, PCI_EXP_DEVCTL, cap[i++]);
>   pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]);
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 5c59365092fa..a660a01358c5 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -111,6 +111,7 @@ void pci_free_cap_save_buffers(struct pci_dev *dev);
>  bool pci_bridge_d3_possible(struct pci_dev *dev);
>  void pci_bridge_d3_update(struct pci_dev *dev);
>  void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev);
> +void pci_reconfigure_bridge_ltr(struct pci_dev *dev);

Nit: calling it pci_bridge_reconfigure_ltr() would match better with the
other function names.

>  
>  static inline void pci_wakeup_event(struct pci_dev *dev)
>  {
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 953f15abc850..fa6075093f3b 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2132,9 +2132,16 @@ static void pci_configure_ltr(struct pci_dev *dev)
>* Complex and all intermediate Switches indicate support for LTR.
>* PCIe r4.0, sec 6.18.
>*/
> - if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
> - ((bridge = pci_upstream_bridge(dev)) &&
> -   bridge->ltr_path)) {
> + if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) {
> + pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,
> +  PCI_EXP_DEVCTL2_LTR_EN);
> + dev->ltr_path = 1;
> + return;
> + }
> +
> + bridge = pci_upstream_bridge(dev);
> + if (bridge && bridge->ltr_path) {
> + pci_reconfigure_bridge_ltr(dev);
>   pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,
>PCI_EXP_DEVCTL2_LTR_EN);
>   dev->ltr_path = 1;
> -- 
> 2.18.0

[v3] PCI: Avoid unsync of LTR mechanism configuration

2021-01-28 Thread mingchuang.qiao 
From: Mingchuang Qiao 

In bus scan flow, the "LTR Mechanism Enable" bit of DEVCTL2 register is
configured in pci_configure_ltr(). If device and bridge both support LTR
mechanism, the "LTR Mechanism Enable" bit of device and bridge will be
enabled in DEVCTL2 register. And pci_dev->ltr_path will be set as 1.

If PCIe link goes down when device resets, the "LTR Mechanism Enable" bit
of bridge will change to 0 according to PCIe r5.0, sec 7.5.3.16. However,
the pci_dev->ltr_path value of bridge is still 1.

For following conditions, check and re-configure "LTR Mechanism Enable" bit
of bridge to make "LTR Mechanism Enable" bit mtach ltr_path value.
   -before configuring device's LTR for hot-remove/hot-add
   -before restoring device's DEVCTL2 register when restore device state

Signed-off-by: Mingchuang Qiao 
---
changes of v2
 -modify patch description
 -reconfigure bridge's LTR before restoring device DEVCTL2 register
changes of v3
 -call pci_reconfigure_bridge_ltr() in probe.c
---
 drivers/pci/pci.c   | 25 +
 drivers/pci/pci.h   |  1 +
 drivers/pci/probe.c | 13 ++---
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b9fecc25d213..12b557c8f062 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1437,6 +1437,24 @@ static int pci_save_pcie_state(struct pci_dev *dev)
return 0;
 }
 
+void pci_reconfigure_bridge_ltr(struct pci_dev *dev)
+{
+#ifdef CONFIG_PCIEASPM
+   struct pci_dev *bridge;
+   u32 ctl;
+
+   bridge = pci_upstream_bridge(dev);
+   if (bridge && bridge->ltr_path) {
+   pcie_capability_read_dword(bridge, PCI_EXP_DEVCTL2, );
+   if (!(ctl & PCI_EXP_DEVCTL2_LTR_EN)) {
+   pci_dbg(bridge, "re-enabling LTR\n");
+   pcie_capability_set_word(bridge, PCI_EXP_DEVCTL2,
+PCI_EXP_DEVCTL2_LTR_EN);
+   }
+   }
+#endif
+}
+
 static void pci_restore_pcie_state(struct pci_dev *dev)
 {
int i = 0;
@@ -1447,6 +1465,13 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
if (!save_state)
return;
 
+   /*
+* Downstream ports reset the LTR enable bit when link goes down.
+* Check and re-configure the bit here before restoring device.
+* PCIe r5.0, sec 7.5.3.16.
+*/
+   pci_reconfigure_bridge_ltr(dev);
+
cap = (u16 *)_state->cap.data[0];
pcie_capability_write_word(dev, PCI_EXP_DEVCTL, cap[i++]);
pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]);
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 5c59365092fa..a660a01358c5 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -111,6 +111,7 @@ void pci_free_cap_save_buffers(struct pci_dev *dev);
 bool pci_bridge_d3_possible(struct pci_dev *dev);
 void pci_bridge_d3_update(struct pci_dev *dev);
 void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev);
+void pci_reconfigure_bridge_ltr(struct pci_dev *dev);
 
 static inline void pci_wakeup_event(struct pci_dev *dev)
 {
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 953f15abc850..fa6075093f3b 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2132,9 +2132,16 @@ static void pci_configure_ltr(struct pci_dev *dev)
 * Complex and all intermediate Switches indicate support for LTR.
 * PCIe r4.0, sec 6.18.
 */
-   if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
-   ((bridge = pci_upstream_bridge(dev)) &&
- bridge->ltr_path)) {
+   if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) {
+   pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,
+PCI_EXP_DEVCTL2_LTR_EN);
+   dev->ltr_path = 1;
+   return;
+   }
+
+   bridge = pci_upstream_bridge(dev);
+   if (bridge && bridge->ltr_path) {
+   pci_reconfigure_bridge_ltr(dev);
pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,
 PCI_EXP_DEVCTL2_LTR_EN);
dev->ltr_path = 1;
-- 
2.18.0