[PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Remi Pommarel]

Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
implemented and does not reflect the actual link training state (the
flag is always set to 0). In order to support link re-training feature
this flag has to be emulated. The Link Training and Status State
Machine (LTSSM) flag in Aardvark LMI config register could be used as
a link training indicator. Indeed if the LTSSM is in L0 or upper state
then link training has completed (see [1]).

Unfortunately because after asking a link retraining it takes a while
for the LTSSM state to become less than 0x10 (due to L0s to recovery
state transition delays), LTSSM can still be in L0 while link training
has not finished yet. So this waits for link to be in recovery or lesser
state before returning after asking for a link retrain.

[1] "PCI Express Base Specification", REV. 4.0
    PCI Express, February 19 2014, Table 4-14

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
---
Changes since v1:
  - Rename retraining flag field
  - Fix DEVCTL register writing

Changes since v2:
  - Rewrite patch logic so it is more legible

Please note that I will unlikely be able to answer any comments from May
24th to June 10th.
---
 drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index 134e0306ff00..8803083b2174 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -180,6 +180,8 @@
 #define LINK_WAIT_MAX_RETRIES		10
 #define LINK_WAIT_USLEEP_MIN		90000
 #define LINK_WAIT_USLEEP_MAX		100000
+#define RETRAIN_WAIT_MAX_RETRIES	10
+#define RETRAIN_WAIT_USLEEP_US		2000
 
 #define MSI_IRQ_NUM			32
 
@@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
 	return -ETIMEDOUT;
 }
 
+static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
+{
+	size_t retries;
+
+	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
+		if (!advk_pcie_link_up(pcie))
+			break;
+		udelay(RETRAIN_WAIT_USLEEP_US);
+	}
+}
+
 static void advk_pcie_setup_hw(struct advk_pcie *pcie)
 {
 	u32 reg;
@@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
 		return PCI_BRIDGE_EMUL_HANDLED;
 	}
 
+	case PCI_EXP_LNKCTL: {
+		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
+		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
+			~(PCI_EXP_LNKSTA_LT << 16);
+		if (!advk_pcie_link_up(pcie))
+			val |= (PCI_EXP_LNKSTA_LT << 16);
+		*value = val;
+		return PCI_BRIDGE_EMUL_HANDLED;
+	}
+
 	case PCI_CAP_LIST_ID:
 	case PCI_EXP_DEVCAP:
 	case PCI_EXP_DEVCTL:
 	case PCI_EXP_LNKCAP:
-	case PCI_EXP_LNKCTL:
 		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
 		return PCI_BRIDGE_EMUL_HANDLED;
 	default:
@@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
 
 	switch (reg) {
 	case PCI_EXP_DEVCTL:
+		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
+		break;
+
 	case PCI_EXP_LNKCTL:
 		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
+		if (new & PCI_EXP_LNKCTL_RL)
+			advk_pcie_wait_for_retrain(pcie);
 		break;
 
 	case PCI_EXP_RTCTL:
-- 
2.20.1

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Remi Pommarel]

On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel wrote:
> Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> implemented and does not reflect the actual link training state (the
> flag is always set to 0). In order to support link re-training feature
> this flag has to be emulated. The Link Training and Status State
> Machine (LTSSM) flag in Aardvark LMI config register could be used as
> a link training indicator. Indeed if the LTSSM is in L0 or upper state
> then link training has completed (see [1]).
> 
> Unfortunately because after asking a link retraining it takes a while
> for the LTSSM state to become less than 0x10 (due to L0s to recovery
> state transition delays), LTSSM can still be in L0 while link training
> has not finished yet. So this waits for link to be in recovery or lesser
> state before returning after asking for a link retrain.
> 
> [1] "PCI Express Base Specification", REV. 4.0
>     PCI Express, February 19 2014, Table 4-14
> 
> Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> ---
> Changes since v1:
>   - Rename retraining flag field
>   - Fix DEVCTL register writing
> 
> Changes since v2:
>   - Rewrite patch logic so it is more legible
> 
> Please note that I will unlikely be able to answer any comments from May
> 24th to June 10th.
> ---
>  drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> index 134e0306ff00..8803083b2174 100644
> --- a/drivers/pci/controller/pci-aardvark.c
> +++ b/drivers/pci/controller/pci-aardvark.c
> @@ -180,6 +180,8 @@
>  #define LINK_WAIT_MAX_RETRIES		10
>  #define LINK_WAIT_USLEEP_MIN		90000
>  #define LINK_WAIT_USLEEP_MAX		100000
> +#define RETRAIN_WAIT_MAX_RETRIES	10
> +#define RETRAIN_WAIT_USLEEP_US		2000
>  
>  #define MSI_IRQ_NUM			32
>  
> @@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
>  	return -ETIMEDOUT;
>  }
>  
> +static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
> +{
> +	size_t retries;
> +
> +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
> +		if (!advk_pcie_link_up(pcie))
> +			break;
> +		udelay(RETRAIN_WAIT_USLEEP_US);
> +	}
> +}
> +
>  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
>  {
>  	u32 reg;
> @@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
>  		return PCI_BRIDGE_EMUL_HANDLED;
>  	}
>  
> +	case PCI_EXP_LNKCTL: {
> +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
> +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
> +			~(PCI_EXP_LNKSTA_LT << 16);
> +		if (!advk_pcie_link_up(pcie))
> +			val |= (PCI_EXP_LNKSTA_LT << 16);
> +		*value = val;
> +		return PCI_BRIDGE_EMUL_HANDLED;
> +	}
> +
>  	case PCI_CAP_LIST_ID:
>  	case PCI_EXP_DEVCAP:
>  	case PCI_EXP_DEVCTL:
>  	case PCI_EXP_LNKCAP:
> -	case PCI_EXP_LNKCTL:
>  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
>  		return PCI_BRIDGE_EMUL_HANDLED;
>  	default:
> @@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
>  
>  	switch (reg) {
>  	case PCI_EXP_DEVCTL:
> +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> +		break;
> +
>  	case PCI_EXP_LNKCTL:
>  		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> +		if (new & PCI_EXP_LNKCTL_RL)
> +			advk_pcie_wait_for_retrain(pcie);
>  		break;
>  
>  	case PCI_EXP_RTCTL:
> -- 
> 2.20.1

Gentle ping.

Please note that the SError problem discussed in V1 has been handled
and merged in arm-trusted-firmware's mainline.

-- 
Remi

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Thomas Petazzoni]

Hello Remi,

On Wed, 22 May 2019 23:33:51 +0200
Remi Pommarel <repk@triplefau.lt> wrote:

> Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> implemented and does not reflect the actual link training state (the
> flag is always set to 0). In order to support link re-training feature
> this flag has to be emulated. The Link Training and Status State
> Machine (LTSSM) flag in Aardvark LMI config register could be used as
> a link training indicator. Indeed if the LTSSM is in L0 or upper state
> then link training has completed (see [1]).
> 
> Unfortunately because after asking a link retraining it takes a while
> for the LTSSM state to become less than 0x10 (due to L0s to recovery
> state transition delays), LTSSM can still be in L0 while link training
> has not finished yet. So this waits for link to be in recovery or lesser
> state before returning after asking for a link retrain.
> 
> [1] "PCI Express Base Specification", REV. 4.0
>     PCI Express, February 19 2014, Table 4-14
> 
> Signed-off-by: Remi Pommarel <repk@triplefau.lt>

Here as well, sorry for the very long delay, and many thanks for the
great research work, including the arm-trusted-firmware fix. I reviewed
the implementation, and tested on my Armada 3720 DB board with a E1000E
NIC, and it all looks good to me.

Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Thanks!

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Andrew Murray]

On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel wrote:
> Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> implemented and does not reflect the actual link training state (the
> flag is always set to 0). In order to support link re-training feature
> this flag has to be emulated. The Link Training and Status State
> Machine (LTSSM) flag in Aardvark LMI config register could be used as
> a link training indicator. Indeed if the LTSSM is in L0 or upper state
> then link training has completed (see [1]).
> 
> Unfortunately because after asking a link retraining it takes a while
> for the LTSSM state to become less than 0x10 (due to L0s to recovery
> state transition delays), LTSSM can still be in L0 while link training
> has not finished yet. So this waits for link to be in recovery or lesser
> state before returning after asking for a link retrain.
> 
> [1] "PCI Express Base Specification", REV. 4.0
>     PCI Express, February 19 2014, Table 4-14
> 
> Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> ---
> Changes since v1:
>   - Rename retraining flag field
>   - Fix DEVCTL register writing
> 
> Changes since v2:
>   - Rewrite patch logic so it is more legible
> 
> Please note that I will unlikely be able to answer any comments from May
> 24th to June 10th.
> ---
>  drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> index 134e0306ff00..8803083b2174 100644
> --- a/drivers/pci/controller/pci-aardvark.c
> +++ b/drivers/pci/controller/pci-aardvark.c
> @@ -180,6 +180,8 @@
>  #define LINK_WAIT_MAX_RETRIES		10
>  #define LINK_WAIT_USLEEP_MIN		90000
>  #define LINK_WAIT_USLEEP_MAX		100000
> +#define RETRAIN_WAIT_MAX_RETRIES	10
> +#define RETRAIN_WAIT_USLEEP_US		2000
>  
>  #define MSI_IRQ_NUM			32
>  
> @@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
>  	return -ETIMEDOUT;
>  }
>  
> +static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
> +{
> +	size_t retries;
> +
> +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
> +		if (!advk_pcie_link_up(pcie))
> +			break;
> +		udelay(RETRAIN_WAIT_USLEEP_US);
> +	}
> +}
> +
>  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
>  {
>  	u32 reg;
> @@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
>  		return PCI_BRIDGE_EMUL_HANDLED;
>  	}
>  
> +	case PCI_EXP_LNKCTL: {
> +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
> +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
> +			~(PCI_EXP_LNKSTA_LT << 16);

The commit message says "the flag is always set to 0" - therefore I guess
you don't *need* to mask out the LT bit here? I assume this is just
belt-and-braces but thought I'd check incase I've misunderstood or if your
commit message is inaccurate.

In any case masking out the bit (or adding a comment) makes this code more
readable as the reader doesn't need to know what the hardware does with this
bit.


> +		if (!advk_pcie_link_up(pcie))
> +			val |= (PCI_EXP_LNKSTA_LT << 16);
> +		*value = val;
> +		return PCI_BRIDGE_EMUL_HANDLED;
> +	}
> +
>  	case PCI_CAP_LIST_ID:
>  	case PCI_EXP_DEVCAP:
>  	case PCI_EXP_DEVCTL:
>  	case PCI_EXP_LNKCAP:
> -	case PCI_EXP_LNKCTL:
>  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
>  		return PCI_BRIDGE_EMUL_HANDLED;
>  	default:
> @@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
>  
>  	switch (reg) {
>  	case PCI_EXP_DEVCTL:
> +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> +		break;

Why is this here?

Thanks,

Andrew Murray

> +
>  	case PCI_EXP_LNKCTL:
>  		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> +		if (new & PCI_EXP_LNKCTL_RL)
> +			advk_pcie_wait_for_retrain(pcie);
>  		break;
>  
>  	case PCI_EXP_RTCTL:
> -- 
> 2.20.1
> 

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Remi Pommarel]

On Mon, Sep 30, 2019 at 04:40:18PM +0100, Andrew Murray wrote:
> On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel wrote:
> > Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> > implemented and does not reflect the actual link training state (the
> > flag is always set to 0). In order to support link re-training feature
> > this flag has to be emulated. The Link Training and Status State
> > Machine (LTSSM) flag in Aardvark LMI config register could be used as
> > a link training indicator. Indeed if the LTSSM is in L0 or upper state
> > then link training has completed (see [1]).
> > 
> > Unfortunately because after asking a link retraining it takes a while
> > for the LTSSM state to become less than 0x10 (due to L0s to recovery
> > state transition delays), LTSSM can still be in L0 while link training
> > has not finished yet. So this waits for link to be in recovery or lesser
> > state before returning after asking for a link retrain.
> > 
> > [1] "PCI Express Base Specification", REV. 4.0
> >     PCI Express, February 19 2014, Table 4-14
> > 
> > Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> > ---
> > Changes since v1:
> >   - Rename retraining flag field
> >   - Fix DEVCTL register writing
> > 
> > Changes since v2:
> >   - Rewrite patch logic so it is more legible
> > 
> > Please note that I will unlikely be able to answer any comments from May
> > 24th to June 10th.
> > ---
> >  drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
> >  1 file changed, 28 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > index 134e0306ff00..8803083b2174 100644
> > --- a/drivers/pci/controller/pci-aardvark.c
> > +++ b/drivers/pci/controller/pci-aardvark.c
> > @@ -180,6 +180,8 @@
> >  #define LINK_WAIT_MAX_RETRIES		10
> >  #define LINK_WAIT_USLEEP_MIN		90000
> >  #define LINK_WAIT_USLEEP_MAX		100000
> > +#define RETRAIN_WAIT_MAX_RETRIES	10
> > +#define RETRAIN_WAIT_USLEEP_US		2000
> >  
> >  #define MSI_IRQ_NUM			32
> >  
> > @@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
> >  	return -ETIMEDOUT;
> >  }
> >  
> > +static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
> > +{
> > +	size_t retries;
> > +
> > +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
> > +		if (!advk_pcie_link_up(pcie))
> > +			break;
> > +		udelay(RETRAIN_WAIT_USLEEP_US);
> > +	}
> > +}
> > +
> >  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
> >  {
> >  	u32 reg;
> > @@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
> >  		return PCI_BRIDGE_EMUL_HANDLED;
> >  	}
> >  
> > +	case PCI_EXP_LNKCTL: {
> > +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
> > +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
> > +			~(PCI_EXP_LNKSTA_LT << 16);
> 
> The commit message says "the flag is always set to 0" - therefore I guess
> you don't *need* to mask out the LT bit here? I assume this is just
> belt-and-braces but thought I'd check incase I've misunderstood or if your
> commit message is inaccurate.
> 
> In any case masking out the bit (or adding a comment) makes this code more
> readable as the reader doesn't need to know what the hardware does with this
> bit.

Actually vendor eventually responded that the bit was reserved, but
during my tests it remains to 0.

So yes I am masking this out mainly for belt-and-braces and legibility.

> > +		if (!advk_pcie_link_up(pcie))
> > +			val |= (PCI_EXP_LNKSTA_LT << 16);
> > +		*value = val;
> > +		return PCI_BRIDGE_EMUL_HANDLED;
> > +	}
> > +
> >  	case PCI_CAP_LIST_ID:
> >  	case PCI_EXP_DEVCAP:
> >  	case PCI_EXP_DEVCTL:
> >  	case PCI_EXP_LNKCAP:
> > -	case PCI_EXP_LNKCTL:
> >  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
> >  		return PCI_BRIDGE_EMUL_HANDLED;
> >  	default:
> > @@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
> >  
> >  	switch (reg) {
> >  	case PCI_EXP_DEVCTL:
> > +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> > +		break;
> 
> Why is this here?
> 

Before PCI_EXP_DEVCTL and PCI_EXP_LNKCTL were doing the same thing, but
as now PCI_EXP_LNKCTL does extra things (i.e. wait for link to
successfully retrain), they do have different behaviours.

So this is here so PCI_EXP_DEVCTL keeps its old behaviour and do not
wait for link retrain in case an unrelated (PCI_EXP_LNKCTL_RL) bit is
set.

-- 
Remi

> > +
> >  	case PCI_EXP_LNKCTL:
> >  		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> > +		if (new & PCI_EXP_LNKCTL_RL)
> > +			advk_pcie_wait_for_retrain(pcie);
> >  		break;
> >  
> >  	case PCI_EXP_RTCTL:
> > -- 
> > 2.20.1
> > 

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Andrew Murray]

On Mon, Sep 30, 2019 at 06:52:30PM +0200, Remi Pommarel wrote:
> On Mon, Sep 30, 2019 at 04:40:18PM +0100, Andrew Murray wrote:
> > On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel wrote:
> > > Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> > > implemented and does not reflect the actual link training state (the
> > > flag is always set to 0). In order to support link re-training feature
> > > this flag has to be emulated. The Link Training and Status State
> > > Machine (LTSSM) flag in Aardvark LMI config register could be used as
> > > a link training indicator. Indeed if the LTSSM is in L0 or upper state
> > > then link training has completed (see [1]).
> > > 
> > > Unfortunately because after asking a link retraining it takes a while
> > > for the LTSSM state to become less than 0x10 (due to L0s to recovery
> > > state transition delays), LTSSM can still be in L0 while link training
> > > has not finished yet. So this waits for link to be in recovery or lesser
> > > state before returning after asking for a link retrain.
> > > 
> > > [1] "PCI Express Base Specification", REV. 4.0
> > >     PCI Express, February 19 2014, Table 4-14
> > > 
> > > Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> > > ---
> > > Changes since v1:
> > >   - Rename retraining flag field
> > >   - Fix DEVCTL register writing
> > > 
> > > Changes since v2:
> > >   - Rewrite patch logic so it is more legible
> > > 
> > > Please note that I will unlikely be able to answer any comments from May
> > > 24th to June 10th.
> > > ---
> > >  drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
> > >  1 file changed, 28 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > > index 134e0306ff00..8803083b2174 100644
> > > --- a/drivers/pci/controller/pci-aardvark.c
> > > +++ b/drivers/pci/controller/pci-aardvark.c
> > > @@ -180,6 +180,8 @@
> > >  #define LINK_WAIT_MAX_RETRIES		10
> > >  #define LINK_WAIT_USLEEP_MIN		90000
> > >  #define LINK_WAIT_USLEEP_MAX		100000
> > > +#define RETRAIN_WAIT_MAX_RETRIES	10
> > > +#define RETRAIN_WAIT_USLEEP_US		2000
> > >  
> > >  #define MSI_IRQ_NUM			32
> > >  
> > > @@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
> > >  	return -ETIMEDOUT;
> > >  }
> > >  
> > > +static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
> > > +{
> > > +	size_t retries;
> > > +
> > > +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
> > > +		if (!advk_pcie_link_up(pcie))
> > > +			break;
> > > +		udelay(RETRAIN_WAIT_USLEEP_US);
> > > +	}
> > > +}
> > > +
> > >  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
> > >  {
> > >  	u32 reg;
> > > @@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
> > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > >  	}
> > >  
> > > +	case PCI_EXP_LNKCTL: {
> > > +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
> > > +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
> > > +			~(PCI_EXP_LNKSTA_LT << 16);
> > 
> > The commit message says "the flag is always set to 0" - therefore I guess
> > you don't *need* to mask out the LT bit here? I assume this is just
> > belt-and-braces but thought I'd check incase I've misunderstood or if your
> > commit message is inaccurate.
> > 
> > In any case masking out the bit (or adding a comment) makes this code more
> > readable as the reader doesn't need to know what the hardware does with this
> > bit.
> 
> Actually vendor eventually responded that the bit was reserved, but
> during my tests it remains to 0.
> 
> So yes I am masking this out mainly for belt-and-braces and legibility.

Thanks for the clarification.

> 
> > > +		if (!advk_pcie_link_up(pcie))
> > > +			val |= (PCI_EXP_LNKSTA_LT << 16);
> > > +		*value = val;
> > > +		return PCI_BRIDGE_EMUL_HANDLED;
> > > +	}
> > > +
> > >  	case PCI_CAP_LIST_ID:
> > >  	case PCI_EXP_DEVCAP:
> > >  	case PCI_EXP_DEVCTL:
> > >  	case PCI_EXP_LNKCAP:
> > > -	case PCI_EXP_LNKCTL:
> > >  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
> > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > >  	default:
> > > @@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
> > >  
> > >  	switch (reg) {
> > >  	case PCI_EXP_DEVCTL:
> > > +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> > > +		break;
> > 
> > Why is this here?
> > 
> 
> Before PCI_EXP_DEVCTL and PCI_EXP_LNKCTL were doing the same thing, but
> as now PCI_EXP_LNKCTL does extra things (i.e. wait for link to
> successfully retrain), they do have different behaviours.
> 
> So this is here so PCI_EXP_DEVCTL keeps its old behaviour and do not
> wait for link retrain in case an unrelated (PCI_EXP_LNKCTL_RL) bit is
> set.

Oh yes, of course!

Thanks and:

Reviewed-by: Andrew Murray <andrew.murray@arm.com>

> 
> -- 
> Remi
> 
> > > +
> > >  	case PCI_EXP_LNKCTL:
> > >  		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> > > +		if (new & PCI_EXP_LNKCTL_RL)
> > > +			advk_pcie_wait_for_retrain(pcie);
> > >  		break;
> > >  
> > >  	case PCI_EXP_RTCTL:
> > > -- 
> > > 2.20.1
> > > 

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Marc Zyngier]

On Tue, 1 Oct 2019 09:05:46 +0100
Andrew Murray <andrew.murray@arm.com> wrote:

Hi Lorenzo,

> On Mon, Sep 30, 2019 at 06:52:30PM +0200, Remi Pommarel wrote:
> > On Mon, Sep 30, 2019 at 04:40:18PM +0100, Andrew Murray wrote:  
> > > On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel wrote:  
> > > > Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> > > > implemented and does not reflect the actual link training state (the
> > > > flag is always set to 0). In order to support link re-training feature
> > > > this flag has to be emulated. The Link Training and Status State
> > > > Machine (LTSSM) flag in Aardvark LMI config register could be used as
> > > > a link training indicator. Indeed if the LTSSM is in L0 or upper state
> > > > then link training has completed (see [1]).
> > > > 
> > > > Unfortunately because after asking a link retraining it takes a while
> > > > for the LTSSM state to become less than 0x10 (due to L0s to recovery
> > > > state transition delays), LTSSM can still be in L0 while link training
> > > > has not finished yet. So this waits for link to be in recovery or lesser
> > > > state before returning after asking for a link retrain.
> > > > 
> > > > [1] "PCI Express Base Specification", REV. 4.0
> > > >     PCI Express, February 19 2014, Table 4-14
> > > > 
> > > > Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> > > > ---
> > > > Changes since v1:
> > > >   - Rename retraining flag field
> > > >   - Fix DEVCTL register writing
> > > > 
> > > > Changes since v2:
> > > >   - Rewrite patch logic so it is more legible
> > > > 
> > > > Please note that I will unlikely be able to answer any comments from May
> > > > 24th to June 10th.
> > > > ---
> > > >  drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
> > > >  1 file changed, 28 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > > > index 134e0306ff00..8803083b2174 100644
> > > > --- a/drivers/pci/controller/pci-aardvark.c
> > > > +++ b/drivers/pci/controller/pci-aardvark.c
> > > > @@ -180,6 +180,8 @@
> > > >  #define LINK_WAIT_MAX_RETRIES		10
> > > >  #define LINK_WAIT_USLEEP_MIN		90000
> > > >  #define LINK_WAIT_USLEEP_MAX		100000
> > > > +#define RETRAIN_WAIT_MAX_RETRIES	10
> > > > +#define RETRAIN_WAIT_USLEEP_US		2000
> > > >  
> > > >  #define MSI_IRQ_NUM			32
> > > >  
> > > > @@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
> > > >  	return -ETIMEDOUT;
> > > >  }
> > > >  
> > > > +static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
> > > > +{
> > > > +	size_t retries;
> > > > +
> > > > +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
> > > > +		if (!advk_pcie_link_up(pcie))
> > > > +			break;
> > > > +		udelay(RETRAIN_WAIT_USLEEP_US);
> > > > +	}
> > > > +}
> > > > +
> > > >  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
> > > >  {
> > > >  	u32 reg;
> > > > @@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
> > > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > > >  	}
> > > >  
> > > > +	case PCI_EXP_LNKCTL: {
> > > > +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
> > > > +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
> > > > +			~(PCI_EXP_LNKSTA_LT << 16);  
> > > 
> > > The commit message says "the flag is always set to 0" - therefore I guess
> > > you don't *need* to mask out the LT bit here? I assume this is just
> > > belt-and-braces but thought I'd check incase I've misunderstood or if your
> > > commit message is inaccurate.
> > > 
> > > In any case masking out the bit (or adding a comment) makes this code more
> > > readable as the reader doesn't need to know what the hardware does with this
> > > bit.  
> > 
> > Actually vendor eventually responded that the bit was reserved, but
> > during my tests it remains to 0.
> > 
> > So yes I am masking this out mainly for belt-and-braces and legibility.  
> 
> Thanks for the clarification.
> 
> >   
> > > > +		if (!advk_pcie_link_up(pcie))
> > > > +			val |= (PCI_EXP_LNKSTA_LT << 16);
> > > > +		*value = val;
> > > > +		return PCI_BRIDGE_EMUL_HANDLED;
> > > > +	}
> > > > +
> > > >  	case PCI_CAP_LIST_ID:
> > > >  	case PCI_EXP_DEVCAP:
> > > >  	case PCI_EXP_DEVCTL:
> > > >  	case PCI_EXP_LNKCAP:
> > > > -	case PCI_EXP_LNKCTL:
> > > >  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
> > > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > > >  	default:
> > > > @@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
> > > >  
> > > >  	switch (reg) {
> > > >  	case PCI_EXP_DEVCTL:
> > > > +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> > > > +		break;  
> > > 
> > > Why is this here?
> > >   
> > 
> > Before PCI_EXP_DEVCTL and PCI_EXP_LNKCTL were doing the same thing, but
> > as now PCI_EXP_LNKCTL does extra things (i.e. wait for link to
> > successfully retrain), they do have different behaviours.
> > 
> > So this is here so PCI_EXP_DEVCTL keeps its old behaviour and do not
> > wait for link retrain in case an unrelated (PCI_EXP_LNKCTL_RL) bit is
> > set.  
> 
> Oh yes, of course!
> 
> Thanks and:
> 
> Reviewed-by: Andrew Murray <andrew.murray@arm.com>

Is there any hope for this workaround to make it into 5.4?

My EspressoBin (which is blessed with this joke of a PCIe controller)
is pretty much a doorstop without it and dies with a SError early at
boot.

FWIW:

Tested-by: Marc Zyngier <maz@kernel.org>

	M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Lorenzo Pieralisi]

On Sun, Oct 13, 2019 at 11:34:15AM +0100, Marc Zyngier wrote:
> On Tue, 1 Oct 2019 09:05:46 +0100
> Andrew Murray <andrew.murray@arm.com> wrote:
> 
> Hi Lorenzo,
> 
> > On Mon, Sep 30, 2019 at 06:52:30PM +0200, Remi Pommarel wrote:
> > > On Mon, Sep 30, 2019 at 04:40:18PM +0100, Andrew Murray wrote:  
> > > > On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel wrote:  
> > > > > Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> > > > > implemented and does not reflect the actual link training state (the
> > > > > flag is always set to 0). In order to support link re-training feature
> > > > > this flag has to be emulated. The Link Training and Status State
> > > > > Machine (LTSSM) flag in Aardvark LMI config register could be used as
> > > > > a link training indicator. Indeed if the LTSSM is in L0 or upper state
> > > > > then link training has completed (see [1]).
> > > > > 
> > > > > Unfortunately because after asking a link retraining it takes a while
> > > > > for the LTSSM state to become less than 0x10 (due to L0s to recovery
> > > > > state transition delays), LTSSM can still be in L0 while link training
> > > > > has not finished yet. So this waits for link to be in recovery or lesser
> > > > > state before returning after asking for a link retrain.
> > > > > 
> > > > > [1] "PCI Express Base Specification", REV. 4.0
> > > > >     PCI Express, February 19 2014, Table 4-14
> > > > > 
> > > > > Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> > > > > ---
> > > > > Changes since v1:
> > > > >   - Rename retraining flag field
> > > > >   - Fix DEVCTL register writing
> > > > > 
> > > > > Changes since v2:
> > > > >   - Rewrite patch logic so it is more legible
> > > > > 
> > > > > Please note that I will unlikely be able to answer any comments from May
> > > > > 24th to June 10th.
> > > > > ---
> > > > >  drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
> > > > >  1 file changed, 28 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > > > > index 134e0306ff00..8803083b2174 100644
> > > > > --- a/drivers/pci/controller/pci-aardvark.c
> > > > > +++ b/drivers/pci/controller/pci-aardvark.c
> > > > > @@ -180,6 +180,8 @@
> > > > >  #define LINK_WAIT_MAX_RETRIES		10
> > > > >  #define LINK_WAIT_USLEEP_MIN		90000
> > > > >  #define LINK_WAIT_USLEEP_MAX		100000
> > > > > +#define RETRAIN_WAIT_MAX_RETRIES	10
> > > > > +#define RETRAIN_WAIT_USLEEP_US		2000
> > > > >  
> > > > >  #define MSI_IRQ_NUM			32
> > > > >  
> > > > > @@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
> > > > >  	return -ETIMEDOUT;
> > > > >  }
> > > > >  
> > > > > +static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
> > > > > +{
> > > > > +	size_t retries;
> > > > > +
> > > > > +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
> > > > > +		if (!advk_pcie_link_up(pcie))
> > > > > +			break;
> > > > > +		udelay(RETRAIN_WAIT_USLEEP_US);
> > > > > +	}
> > > > > +}
> > > > > +
> > > > >  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
> > > > >  {
> > > > >  	u32 reg;
> > > > > @@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
> > > > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > > > >  	}
> > > > >  
> > > > > +	case PCI_EXP_LNKCTL: {
> > > > > +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
> > > > > +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
> > > > > +			~(PCI_EXP_LNKSTA_LT << 16);  
> > > > 
> > > > The commit message says "the flag is always set to 0" - therefore I guess
> > > > you don't *need* to mask out the LT bit here? I assume this is just
> > > > belt-and-braces but thought I'd check incase I've misunderstood or if your
> > > > commit message is inaccurate.
> > > > 
> > > > In any case masking out the bit (or adding a comment) makes this code more
> > > > readable as the reader doesn't need to know what the hardware does with this
> > > > bit.  
> > > 
> > > Actually vendor eventually responded that the bit was reserved, but
> > > during my tests it remains to 0.
> > > 
> > > So yes I am masking this out mainly for belt-and-braces and legibility.  
> > 
> > Thanks for the clarification.
> > 
> > >   
> > > > > +		if (!advk_pcie_link_up(pcie))
> > > > > +			val |= (PCI_EXP_LNKSTA_LT << 16);
> > > > > +		*value = val;
> > > > > +		return PCI_BRIDGE_EMUL_HANDLED;
> > > > > +	}
> > > > > +
> > > > >  	case PCI_CAP_LIST_ID:
> > > > >  	case PCI_EXP_DEVCAP:
> > > > >  	case PCI_EXP_DEVCTL:
> > > > >  	case PCI_EXP_LNKCAP:
> > > > > -	case PCI_EXP_LNKCTL:
> > > > >  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
> > > > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > > > >  	default:
> > > > > @@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
> > > > >  
> > > > >  	switch (reg) {
> > > > >  	case PCI_EXP_DEVCTL:
> > > > > +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> > > > > +		break;  
> > > > 
> > > > Why is this here?
> > > >   
> > > 
> > > Before PCI_EXP_DEVCTL and PCI_EXP_LNKCTL were doing the same thing, but
> > > as now PCI_EXP_LNKCTL does extra things (i.e. wait for link to
> > > successfully retrain), they do have different behaviours.
> > > 
> > > So this is here so PCI_EXP_DEVCTL keeps its old behaviour and do not
> > > wait for link retrain in case an unrelated (PCI_EXP_LNKCTL_RL) bit is
> > > set.  
> > 
> > Oh yes, of course!
> > 
> > Thanks and:
> > 
> > Reviewed-by: Andrew Murray <andrew.murray@arm.com>
> 
> Is there any hope for this workaround to make it into 5.4?
> 
> My EspressoBin (which is blessed with this joke of a PCIe controller)
> is pretty much a doorstop without it and dies with a SError early at
> boot.
> 
> FWIW:
> 
> Tested-by: Marc Zyngier <maz@kernel.org>

Hi Marc,

First thing I will have to mark it as a Fixes: (if Remi can provide
me with a tag that'd be great), usually we send fixes at -rc* for
patches that fix code that went in the current (eg 5.4) material,
I will ask Bjorn to see if we can send this in one of the upcoming
-rc* even if it fixes older code.

Thanks,
Lorenzo

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Remi Pommarel]

Hi Lorenzo, Marc,

On Mon, Oct 14, 2019 at 11:01:29AM +0100, Lorenzo Pieralisi wrote:
> On Sun, Oct 13, 2019 at 11:34:15AM +0100, Marc Zyngier wrote:
> > On Tue, 1 Oct 2019 09:05:46 +0100
> > Andrew Murray <andrew.murray@arm.com> wrote:
> > 
> > Hi Lorenzo,
> > 
> > > On Mon, Sep 30, 2019 at 06:52:30PM +0200, Remi Pommarel wrote:
> > > > On Mon, Sep 30, 2019 at 04:40:18PM +0100, Andrew Murray wrote:  
> > > > > On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel wrote:  
> > > > > > Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> > > > > > implemented and does not reflect the actual link training state (the
> > > > > > flag is always set to 0). In order to support link re-training feature
> > > > > > this flag has to be emulated. The Link Training and Status State
> > > > > > Machine (LTSSM) flag in Aardvark LMI config register could be used as
> > > > > > a link training indicator. Indeed if the LTSSM is in L0 or upper state
> > > > > > then link training has completed (see [1]).
> > > > > > 
> > > > > > Unfortunately because after asking a link retraining it takes a while
> > > > > > for the LTSSM state to become less than 0x10 (due to L0s to recovery
> > > > > > state transition delays), LTSSM can still be in L0 while link training
> > > > > > has not finished yet. So this waits for link to be in recovery or lesser
> > > > > > state before returning after asking for a link retrain.
> > > > > > 
> > > > > > [1] "PCI Express Base Specification", REV. 4.0
> > > > > >     PCI Express, February 19 2014, Table 4-14
> > > > > > 
> > > > > > Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> > > > > > ---
> > > > > > Changes since v1:
> > > > > >   - Rename retraining flag field
> > > > > >   - Fix DEVCTL register writing
> > > > > > 
> > > > > > Changes since v2:
> > > > > >   - Rewrite patch logic so it is more legible
> > > > > > 
> > > > > > Please note that I will unlikely be able to answer any comments from May
> > > > > > 24th to June 10th.
> > > > > > ---
> > > > > >  drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
> > > > > >  1 file changed, 28 insertions(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > > > > > index 134e0306ff00..8803083b2174 100644
> > > > > > --- a/drivers/pci/controller/pci-aardvark.c
> > > > > > +++ b/drivers/pci/controller/pci-aardvark.c
> > > > > > @@ -180,6 +180,8 @@
> > > > > >  #define LINK_WAIT_MAX_RETRIES		10
> > > > > >  #define LINK_WAIT_USLEEP_MIN		90000
> > > > > >  #define LINK_WAIT_USLEEP_MAX		100000
> > > > > > +#define RETRAIN_WAIT_MAX_RETRIES	10
> > > > > > +#define RETRAIN_WAIT_USLEEP_US		2000
> > > > > >  
> > > > > >  #define MSI_IRQ_NUM			32
> > > > > >  
> > > > > > @@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
> > > > > >  	return -ETIMEDOUT;
> > > > > >  }
> > > > > >  
> > > > > > +static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
> > > > > > +{
> > > > > > +	size_t retries;
> > > > > > +
> > > > > > +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
> > > > > > +		if (!advk_pcie_link_up(pcie))
> > > > > > +			break;
> > > > > > +		udelay(RETRAIN_WAIT_USLEEP_US);
> > > > > > +	}
> > > > > > +}
> > > > > > +
> > > > > >  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
> > > > > >  {
> > > > > >  	u32 reg;
> > > > > > @@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
> > > > > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > > > > >  	}
> > > > > >  
> > > > > > +	case PCI_EXP_LNKCTL: {
> > > > > > +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
> > > > > > +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
> > > > > > +			~(PCI_EXP_LNKSTA_LT << 16);  
> > > > > 
> > > > > The commit message says "the flag is always set to 0" - therefore I guess
> > > > > you don't *need* to mask out the LT bit here? I assume this is just
> > > > > belt-and-braces but thought I'd check incase I've misunderstood or if your
> > > > > commit message is inaccurate.
> > > > > 
> > > > > In any case masking out the bit (or adding a comment) makes this code more
> > > > > readable as the reader doesn't need to know what the hardware does with this
> > > > > bit.  
> > > > 
> > > > Actually vendor eventually responded that the bit was reserved, but
> > > > during my tests it remains to 0.
> > > > 
> > > > So yes I am masking this out mainly for belt-and-braces and legibility.  
> > > 
> > > Thanks for the clarification.
> > > 
> > > >   
> > > > > > +		if (!advk_pcie_link_up(pcie))
> > > > > > +			val |= (PCI_EXP_LNKSTA_LT << 16);
> > > > > > +		*value = val;
> > > > > > +		return PCI_BRIDGE_EMUL_HANDLED;
> > > > > > +	}
> > > > > > +
> > > > > >  	case PCI_CAP_LIST_ID:
> > > > > >  	case PCI_EXP_DEVCAP:
> > > > > >  	case PCI_EXP_DEVCTL:
> > > > > >  	case PCI_EXP_LNKCAP:
> > > > > > -	case PCI_EXP_LNKCTL:
> > > > > >  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
> > > > > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > > > > >  	default:
> > > > > > @@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
> > > > > >  
> > > > > >  	switch (reg) {
> > > > > >  	case PCI_EXP_DEVCTL:
> > > > > > +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> > > > > > +		break;  
> > > > > 
> > > > > Why is this here?
> > > > >   
> > > > 
> > > > Before PCI_EXP_DEVCTL and PCI_EXP_LNKCTL were doing the same thing, but
> > > > as now PCI_EXP_LNKCTL does extra things (i.e. wait for link to
> > > > successfully retrain), they do have different behaviours.
> > > > 
> > > > So this is here so PCI_EXP_DEVCTL keeps its old behaviour and do not
> > > > wait for link retrain in case an unrelated (PCI_EXP_LNKCTL_RL) bit is
> > > > set.  
> > > 
> > > Oh yes, of course!
> > > 
> > > Thanks and:
> > > 
> > > Reviewed-by: Andrew Murray <andrew.murray@arm.com>
> > 
> > Is there any hope for this workaround to make it into 5.4?
> > 
> > My EspressoBin (which is blessed with this joke of a PCIe controller)
> > is pretty much a doorstop without it and dies with a SError early at
> > boot.
> > 
> > FWIW:
> > 
> > Tested-by: Marc Zyngier <maz@kernel.org>
> 
> Hi Marc,
> 
> First thing I will have to mark it as a Fixes: (if Remi can provide
> me with a tag that'd be great), usually we send fixes at -rc* for
> patches that fix code that went in the current (eg 5.4) material,
> I will ask Bjorn to see if we can send this in one of the upcoming
> -rc* even if it fixes older code.

Sure, I think this could be considered a fix for the following commit :
Fixes: 8a3ebd8de328 ("PCI: aardvark: Implement emulated root PCI bridge config space")

Moreover, Marc, I am also a bit supprised that you did not have to use
[1] to even be able to boot.

Also if you want to be completely immune to this kind of SError (that
could theoretically happen if the link goes down for other reasons than
being retrained) you would have to use mainline ATF along with [2]. But
the chances to hit that are low (could only happen in case of link
errors).

[1] [v3] PCI: aardvark: Use LTSSM state to build link training flag
    https://patchwork.ozlabs.org/patch/1115864/
[2] [v3] PCI: aardvark: Don't rely on jiffies while holding spinlock
    https://patchwork.ozlabs.org/patch/1168349/

-- 
Remi

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Marc Zyngier]

Hi Remi,

On 2019-10-14 14:06, Remi Pommarel wrote:
> Hi Lorenzo, Marc,
>
> On Mon, Oct 14, 2019 at 11:01:29AM +0100, Lorenzo Pieralisi wrote:
>> On Sun, Oct 13, 2019 at 11:34:15AM +0100, Marc Zyngier wrote:
>> > On Tue, 1 Oct 2019 09:05:46 +0100
>> > Andrew Murray <andrew.murray@arm.com> wrote:
>> >
>> > Hi Lorenzo,
>> >
>> > > On Mon, Sep 30, 2019 at 06:52:30PM +0200, Remi Pommarel wrote:
>> > > > On Mon, Sep 30, 2019 at 04:40:18PM +0100, Andrew Murray wrote:
>> > > > > On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel 
>> wrote:
>> > > > > > Aardvark's PCI_EXP_LNKSTA_LT flag in its link status 
>> register is not
>> > > > > > implemented and does not reflect the actual link training 
>> state (the
>> > > > > > flag is always set to 0). In order to support link 
>> re-training feature
>> > > > > > this flag has to be emulated. The Link Training and Status 
>> State
>> > > > > > Machine (LTSSM) flag in Aardvark LMI config register could 
>> be used as
>> > > > > > a link training indicator. Indeed if the LTSSM is in L0 or 
>> upper state
>> > > > > > then link training has completed (see [1]).
>> > > > > >
>> > > > > > Unfortunately because after asking a link retraining it 
>> takes a while
>> > > > > > for the LTSSM state to become less than 0x10 (due to L0s 
>> to recovery
>> > > > > > state transition delays), LTSSM can still be in L0 while 
>> link training
>> > > > > > has not finished yet. So this waits for link to be in 
>> recovery or lesser
>> > > > > > state before returning after asking for a link retrain.
>> > > > > >
>> > > > > > [1] "PCI Express Base Specification", REV. 4.0
>> > > > > >     PCI Express, February 19 2014, Table 4-14
>> > > > > >
>> > > > > > Signed-off-by: Remi Pommarel <repk@triplefau.lt>
>> > > > > > ---
>> > > > > > Changes since v1:
>> > > > > >   - Rename retraining flag field
>> > > > > >   - Fix DEVCTL register writing
>> > > > > >
>> > > > > > Changes since v2:
>> > > > > >   - Rewrite patch logic so it is more legible
>> > > > > >
>> > > > > > Please note that I will unlikely be able to answer any 
>> comments from May
>> > > > > > 24th to June 10th.
>> > > > > > ---
>> > > > > >  drivers/pci/controller/pci-aardvark.c | 29 
>> ++++++++++++++++++++++++++-
>> > > > > >  1 file changed, 28 insertions(+), 1 deletion(-)
>> > > > > >
>> > > > > > diff --git a/drivers/pci/controller/pci-aardvark.c 
>> b/drivers/pci/controller/pci-aardvark.c
>> > > > > > index 134e0306ff00..8803083b2174 100644
>> > > > > > --- a/drivers/pci/controller/pci-aardvark.c
>> > > > > > +++ b/drivers/pci/controller/pci-aardvark.c
>> > > > > > @@ -180,6 +180,8 @@
>> > > > > >  #define LINK_WAIT_MAX_RETRIES		10
>> > > > > >  #define LINK_WAIT_USLEEP_MIN		90000
>> > > > > >  #define LINK_WAIT_USLEEP_MAX		100000
>> > > > > > +#define RETRAIN_WAIT_MAX_RETRIES	10
>> > > > > > +#define RETRAIN_WAIT_USLEEP_US		2000
>> > > > > >
>> > > > > >  #define MSI_IRQ_NUM			32
>> > > > > >
>> > > > > > @@ -239,6 +241,17 @@ static int 
>> advk_pcie_wait_for_link(struct advk_pcie *pcie)
>> > > > > >  	return -ETIMEDOUT;
>> > > > > >  }
>> > > > > >
>> > > > > > +static void advk_pcie_wait_for_retrain(struct advk_pcie 
>> *pcie)
>> > > > > > +{
>> > > > > > +	size_t retries;
>> > > > > > +
>> > > > > > +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; 
>> ++retries) {
>> > > > > > +		if (!advk_pcie_link_up(pcie))
>> > > > > > +			break;
>> > > > > > +		udelay(RETRAIN_WAIT_USLEEP_US);
>> > > > > > +	}
>> > > > > > +}
>> > > > > > +
>> > > > > >  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
>> > > > > >  {
>> > > > > >  	u32 reg;
>> > > > > > @@ -426,11 +439,20 @@ 
>> advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
>> > > > > >  		return PCI_BRIDGE_EMUL_HANDLED;
>> > > > > >  	}
>> > > > > >
>> > > > > > +	case PCI_EXP_LNKCTL: {
>> > > > > > +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA 
>> */
>> > > > > > +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) 
>> &
>> > > > > > +			~(PCI_EXP_LNKSTA_LT << 16);
>> > > > >
>> > > > > The commit message says "the flag is always set to 0" - 
>> therefore I guess
>> > > > > you don't *need* to mask out the LT bit here? I assume this 
>> is just
>> > > > > belt-and-braces but thought I'd check incase I've 
>> misunderstood or if your
>> > > > > commit message is inaccurate.
>> > > > >
>> > > > > In any case masking out the bit (or adding a comment) makes 
>> this code more
>> > > > > readable as the reader doesn't need to know what the 
>> hardware does with this
>> > > > > bit.
>> > > >
>> > > > Actually vendor eventually responded that the bit was 
>> reserved, but
>> > > > during my tests it remains to 0.
>> > > >
>> > > > So yes I am masking this out mainly for belt-and-braces and 
>> legibility.
>> > >
>> > > Thanks for the clarification.
>> > >
>> > > >
>> > > > > > +		if (!advk_pcie_link_up(pcie))
>> > > > > > +			val |= (PCI_EXP_LNKSTA_LT << 16);
>> > > > > > +		*value = val;
>> > > > > > +		return PCI_BRIDGE_EMUL_HANDLED;
>> > > > > > +	}
>> > > > > > +
>> > > > > >  	case PCI_CAP_LIST_ID:
>> > > > > >  	case PCI_EXP_DEVCAP:
>> > > > > >  	case PCI_EXP_DEVCTL:
>> > > > > >  	case PCI_EXP_LNKCAP:
>> > > > > > -	case PCI_EXP_LNKCTL:
>> > > > > >  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
>> > > > > >  		return PCI_BRIDGE_EMUL_HANDLED;
>> > > > > >  	default:
>> > > > > > @@ -447,8 +469,13 @@ 
>> advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
>> > > > > >
>> > > > > >  	switch (reg) {
>> > > > > >  	case PCI_EXP_DEVCTL:
>> > > > > > +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
>> > > > > > +		break;
>> > > > >
>> > > > > Why is this here?
>> > > > >
>> > > >
>> > > > Before PCI_EXP_DEVCTL and PCI_EXP_LNKCTL were doing the same 
>> thing, but
>> > > > as now PCI_EXP_LNKCTL does extra things (i.e. wait for link to
>> > > > successfully retrain), they do have different behaviours.
>> > > >
>> > > > So this is here so PCI_EXP_DEVCTL keeps its old behaviour and 
>> do not
>> > > > wait for link retrain in case an unrelated (PCI_EXP_LNKCTL_RL) 
>> bit is
>> > > > set.
>> > >
>> > > Oh yes, of course!
>> > >
>> > > Thanks and:
>> > >
>> > > Reviewed-by: Andrew Murray <andrew.murray@arm.com>
>> >
>> > Is there any hope for this workaround to make it into 5.4?
>> >
>> > My EspressoBin (which is blessed with this joke of a PCIe 
>> controller)
>> > is pretty much a doorstop without it and dies with a SError early 
>> at
>> > boot.
>> >
>> > FWIW:
>> >
>> > Tested-by: Marc Zyngier <maz@kernel.org>
>>
>> Hi Marc,
>>
>> First thing I will have to mark it as a Fixes: (if Remi can provide
>> me with a tag that'd be great), usually we send fixes at -rc* for
>> patches that fix code that went in the current (eg 5.4) material,
>> I will ask Bjorn to see if we can send this in one of the upcoming
>> -rc* even if it fixes older code.
>
> Sure, I think this could be considered a fix for the following commit 
> :
> Fixes: 8a3ebd8de328 ("PCI: aardvark: Implement emulated root PCI
> bridge config space")
>
> Moreover, Marc, I am also a bit supprised that you did not have to 
> use
> [1] to even be able to boot.

No, I don't have that one, and yet the system boots fine (although PCI
doesn't get much use on this box). I guess I'm lucky...

> Also if you want to be completely immune to this kind of SError (that
> could theoretically happen if the link goes down for other reasons 
> than
> being retrained) you would have to use mainline ATF along with [2]. 
> But
> the chances to hit that are low (could only happen in case of link
> errors).

Now you've got me worried. Can you point me to that ATF patch? I'm 
quite
curious as to how you recover from an SError on a v8.0 CPU given that 
it
has no syndrome information and may as well signal "CPU on fire!"...

Thanks,

         M.

>
> [1] [v3] PCI: aardvark: Use LTSSM state to build link training flag
>     https://patchwork.ozlabs.org/patch/1115864/
> [2] [v3] PCI: aardvark: Don't rely on jiffies while holding spinlock
>     https://patchwork.ozlabs.org/patch/1168349/

-- 
Jazz is not dead. It just smells funny...

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Remi Pommarel]

On Mon, Oct 14, 2019 at 02:45:34PM +0100, Marc Zyngier wrote:
> Hi Remi,
> 
> On 2019-10-14 14:06, Remi Pommarel wrote:
> > Hi Lorenzo, Marc,
> > 
> > On Mon, Oct 14, 2019 at 11:01:29AM +0100, Lorenzo Pieralisi wrote:
> > > On Sun, Oct 13, 2019 at 11:34:15AM +0100, Marc Zyngier wrote:
> > > > On Tue, 1 Oct 2019 09:05:46 +0100
> > > > Andrew Murray <andrew.murray@arm.com> wrote:
> > > >
> > > > Hi Lorenzo,
> > > >
> > > > > On Mon, Sep 30, 2019 at 06:52:30PM +0200, Remi Pommarel wrote:
> > > > > > On Mon, Sep 30, 2019 at 04:40:18PM +0100, Andrew Murray wrote:
> > > > > > > On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel
> > > wrote:
> > > > > > > > Aardvark's PCI_EXP_LNKSTA_LT flag in its link status
> > > register is not
> > > > > > > > implemented and does not reflect the actual link training
> > > state (the
> > > > > > > > flag is always set to 0). In order to support link
> > > re-training feature
> > > > > > > > this flag has to be emulated. The Link Training and Status
> > > State
> > > > > > > > Machine (LTSSM) flag in Aardvark LMI config register could
> > > be used as
> > > > > > > > a link training indicator. Indeed if the LTSSM is in L0 or
> > > upper state
> > > > > > > > then link training has completed (see [1]).
> > > > > > > >
> > > > > > > > Unfortunately because after asking a link retraining it
> > > takes a while
> > > > > > > > for the LTSSM state to become less than 0x10 (due to L0s
> > > to recovery
> > > > > > > > state transition delays), LTSSM can still be in L0 while
> > > link training
> > > > > > > > has not finished yet. So this waits for link to be in
> > > recovery or lesser
> > > > > > > > state before returning after asking for a link retrain.
> > > > > > > >
> > > > > > > > [1] "PCI Express Base Specification", REV. 4.0
> > > > > > > >     PCI Express, February 19 2014, Table 4-14
> > > > > > > >
> > > > > > > > Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> > > > > > > > ---
> > > > > > > > Changes since v1:
> > > > > > > >   - Rename retraining flag field
> > > > > > > >   - Fix DEVCTL register writing
> > > > > > > >
> > > > > > > > Changes since v2:
> > > > > > > >   - Rewrite patch logic so it is more legible
> > > > > > > >
> > > > > > > > Please note that I will unlikely be able to answer any
> > > comments from May
> > > > > > > > 24th to June 10th.
> > > > > > > > ---
> > > > > > > >  drivers/pci/controller/pci-aardvark.c | 29
> > > ++++++++++++++++++++++++++-
> > > > > > > >  1 file changed, 28 insertions(+), 1 deletion(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/pci/controller/pci-aardvark.c
> > > b/drivers/pci/controller/pci-aardvark.c
> > > > > > > > index 134e0306ff00..8803083b2174 100644
> > > > > > > > --- a/drivers/pci/controller/pci-aardvark.c
> > > > > > > > +++ b/drivers/pci/controller/pci-aardvark.c
> > > > > > > > @@ -180,6 +180,8 @@
> > > > > > > >  #define LINK_WAIT_MAX_RETRIES		10
> > > > > > > >  #define LINK_WAIT_USLEEP_MIN		90000
> > > > > > > >  #define LINK_WAIT_USLEEP_MAX		100000
> > > > > > > > +#define RETRAIN_WAIT_MAX_RETRIES	10
> > > > > > > > +#define RETRAIN_WAIT_USLEEP_US		2000
> > > > > > > >
> > > > > > > >  #define MSI_IRQ_NUM			32
> > > > > > > >
> > > > > > > > @@ -239,6 +241,17 @@ static int
> > > advk_pcie_wait_for_link(struct advk_pcie *pcie)
> > > > > > > >  	return -ETIMEDOUT;
> > > > > > > >  }
> > > > > > > >
> > > > > > > > +static void advk_pcie_wait_for_retrain(struct advk_pcie
> > > *pcie)
> > > > > > > > +{
> > > > > > > > +	size_t retries;
> > > > > > > > +
> > > > > > > > +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES;
> > > ++retries) {
> > > > > > > > +		if (!advk_pcie_link_up(pcie))
> > > > > > > > +			break;
> > > > > > > > +		udelay(RETRAIN_WAIT_USLEEP_US);
> > > > > > > > +	}
> > > > > > > > +}
> > > > > > > > +
> > > > > > > >  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
> > > > > > > >  {
> > > > > > > >  	u32 reg;
> > > > > > > > @@ -426,11 +439,20 @@
> > > advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
> > > > > > > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > > > > > > >  	}
> > > > > > > >
> > > > > > > > +	case PCI_EXP_LNKCTL: {
> > > > > > > > +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA
> > > */
> > > > > > > > +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg)
> > > &
> > > > > > > > +			~(PCI_EXP_LNKSTA_LT << 16);
> > > > > > >
> > > > > > > The commit message says "the flag is always set to 0" -
> > > therefore I guess
> > > > > > > you don't *need* to mask out the LT bit here? I assume this
> > > is just
> > > > > > > belt-and-braces but thought I'd check incase I've
> > > misunderstood or if your
> > > > > > > commit message is inaccurate.
> > > > > > >
> > > > > > > In any case masking out the bit (or adding a comment) makes
> > > this code more
> > > > > > > readable as the reader doesn't need to know what the
> > > hardware does with this
> > > > > > > bit.
> > > > > >
> > > > > > Actually vendor eventually responded that the bit was
> > > reserved, but
> > > > > > during my tests it remains to 0.
> > > > > >
> > > > > > So yes I am masking this out mainly for belt-and-braces and
> > > legibility.
> > > > >
> > > > > Thanks for the clarification.
> > > > >
> > > > > >
> > > > > > > > +		if (!advk_pcie_link_up(pcie))
> > > > > > > > +			val |= (PCI_EXP_LNKSTA_LT << 16);
> > > > > > > > +		*value = val;
> > > > > > > > +		return PCI_BRIDGE_EMUL_HANDLED;
> > > > > > > > +	}
> > > > > > > > +
> > > > > > > >  	case PCI_CAP_LIST_ID:
> > > > > > > >  	case PCI_EXP_DEVCAP:
> > > > > > > >  	case PCI_EXP_DEVCTL:
> > > > > > > >  	case PCI_EXP_LNKCAP:
> > > > > > > > -	case PCI_EXP_LNKCTL:
> > > > > > > >  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
> > > > > > > >  		return PCI_BRIDGE_EMUL_HANDLED;
> > > > > > > >  	default:
> > > > > > > > @@ -447,8 +469,13 @@
> > > advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
> > > > > > > >
> > > > > > > >  	switch (reg) {
> > > > > > > >  	case PCI_EXP_DEVCTL:
> > > > > > > > +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> > > > > > > > +		break;
> > > > > > >
> > > > > > > Why is this here?
> > > > > > >
> > > > > >
> > > > > > Before PCI_EXP_DEVCTL and PCI_EXP_LNKCTL were doing the same
> > > thing, but
> > > > > > as now PCI_EXP_LNKCTL does extra things (i.e. wait for link to
> > > > > > successfully retrain), they do have different behaviours.
> > > > > >
> > > > > > So this is here so PCI_EXP_DEVCTL keeps its old behaviour and
> > > do not
> > > > > > wait for link retrain in case an unrelated (PCI_EXP_LNKCTL_RL)
> > > bit is
> > > > > > set.
> > > > >
> > > > > Oh yes, of course!
> > > > >
> > > > > Thanks and:
> > > > >
> > > > > Reviewed-by: Andrew Murray <andrew.murray@arm.com>
> > > >
> > > > Is there any hope for this workaround to make it into 5.4?
> > > >
> > > > My EspressoBin (which is blessed with this joke of a PCIe
> > > controller)
> > > > is pretty much a doorstop without it and dies with a SError early
> > > at
> > > > boot.
> > > >
> > > > FWIW:
> > > >
> > > > Tested-by: Marc Zyngier <maz@kernel.org>
> > > 
> > > Hi Marc,
> > > 
> > > First thing I will have to mark it as a Fixes: (if Remi can provide
> > > me with a tag that'd be great), usually we send fixes at -rc* for
> > > patches that fix code that went in the current (eg 5.4) material,
> > > I will ask Bjorn to see if we can send this in one of the upcoming
> > > -rc* even if it fixes older code.
> > 
> > Sure, I think this could be considered a fix for the following commit :
> > Fixes: 8a3ebd8de328 ("PCI: aardvark: Implement emulated root PCI
> > bridge config space")
> > 
> > Moreover, Marc, I am also a bit supprised that you did not have to use
> > [1] to even be able to boot.
> 
> No, I don't have that one, and yet the system boots fine (although PCI
> doesn't get much use on this box). I guess I'm lucky...
> 
> > Also if you want to be completely immune to this kind of SError (that
> > could theoretically happen if the link goes down for other reasons than
> > being retrained) you would have to use mainline ATF along with [2]. But
> > the chances to hit that are low (could only happen in case of link
> > errors).
> 
> Now you've got me worried. Can you point me to that ATF patch? I'm quite
> curious as to how you recover from an SError on a v8.0 CPU given that it
> has no syndrome information and may as well signal "CPU on fire!"...
> 

The patch is at [1]. Please note that this is done quite similarly for
rcar.

[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/1541

-- 
Remi

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Marc Zyngier]

On 2019-10-14 15:00, Remi Pommarel wrote:
> On Mon, Oct 14, 2019 at 02:45:34PM +0100, Marc Zyngier wrote:
>> Hi Remi,
>>
>> On 2019-10-14 14:06, Remi Pommarel wrote:
>> > Hi Lorenzo, Marc,

[...]

>> > Sure, I think this could be considered a fix for the following 
>> commit :
>> > Fixes: 8a3ebd8de328 ("PCI: aardvark: Implement emulated root PCI
>> > bridge config space")
>> >
>> > Moreover, Marc, I am also a bit supprised that you did not have to 
>> use
>> > [1] to even be able to boot.
>>
>> No, I don't have that one, and yet the system boots fine (although 
>> PCI
>> doesn't get much use on this box). I guess I'm lucky...
>>
>> > Also if you want to be completely immune to this kind of SError 
>> (that
>> > could theoretically happen if the link goes down for other reasons 
>> than
>> > being retrained) you would have to use mainline ATF along with 
>> [2]. But
>> > the chances to hit that are low (could only happen in case of link
>> > errors).
>>
>> Now you've got me worried. Can you point me to that ATF patch? I'm 
>> quite
>> curious as to how you recover from an SError on a v8.0 CPU given 
>> that it
>> has no syndrome information and may as well signal "CPU on fire!"...
>>
>
> The patch is at [1]. Please note that this is done quite similarly 
> for
> rcar.
>
> [1] 
> https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/1541

That patch, without any other information, looks quite flaky. Unless 
there
is a strong guarantee that ESR_EL3.ISS==2 only when the PCIe controller
goes wrong, it looks like this only papers over the issue...

That's pretty much independent from the patch at hand in this thread, 
but
I certainly wouldn't trust this ATF patch without some more information
about how the fault is reported to the CPU.

         M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH v3] PCI: aardvark: Use LTSSM state to build link training flag

[Lorenzo Pieralisi]

On Wed, May 22, 2019 at 11:33:51PM +0200, Remi Pommarel wrote:
> Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not
> implemented and does not reflect the actual link training state (the
> flag is always set to 0). In order to support link re-training feature
> this flag has to be emulated. The Link Training and Status State
> Machine (LTSSM) flag in Aardvark LMI config register could be used as
> a link training indicator. Indeed if the LTSSM is in L0 or upper state
> then link training has completed (see [1]).
> 
> Unfortunately because after asking a link retraining it takes a while
> for the LTSSM state to become less than 0x10 (due to L0s to recovery
> state transition delays), LTSSM can still be in L0 while link training
> has not finished yet. So this waits for link to be in recovery or lesser
> state before returning after asking for a link retrain.
> 
> [1] "PCI Express Base Specification", REV. 4.0
>     PCI Express, February 19 2014, Table 4-14
> 
> Signed-off-by: Remi Pommarel <repk@triplefau.lt>
> ---
> Changes since v1:
>   - Rename retraining flag field
>   - Fix DEVCTL register writing
> 
> Changes since v2:
>   - Rewrite patch logic so it is more legible
> 
> Please note that I will unlikely be able to answer any comments from May
> 24th to June 10th.
> ---
>  drivers/pci/controller/pci-aardvark.c | 29 ++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)

Merged in pci/aardvark, to be decided if we target one of the
upcoming -rc* or v5.5.

Thanks and apologies for the delay.

Lorenzo

> 
> diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> index 134e0306ff00..8803083b2174 100644
> --- a/drivers/pci/controller/pci-aardvark.c
> +++ b/drivers/pci/controller/pci-aardvark.c
> @@ -180,6 +180,8 @@
>  #define LINK_WAIT_MAX_RETRIES		10
>  #define LINK_WAIT_USLEEP_MIN		90000
>  #define LINK_WAIT_USLEEP_MAX		100000
> +#define RETRAIN_WAIT_MAX_RETRIES	10
> +#define RETRAIN_WAIT_USLEEP_US		2000
>  
>  #define MSI_IRQ_NUM			32
>  
> @@ -239,6 +241,17 @@ static int advk_pcie_wait_for_link(struct advk_pcie *pcie)
>  	return -ETIMEDOUT;
>  }
>  
> +static void advk_pcie_wait_for_retrain(struct advk_pcie *pcie)
> +{
> +	size_t retries;
> +
> +	for (retries = 0; retries < RETRAIN_WAIT_MAX_RETRIES; ++retries) {
> +		if (!advk_pcie_link_up(pcie))
> +			break;
> +		udelay(RETRAIN_WAIT_USLEEP_US);
> +	}
> +}
> +
>  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
>  {
>  	u32 reg;
> @@ -426,11 +439,20 @@ advk_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge,
>  		return PCI_BRIDGE_EMUL_HANDLED;
>  	}
>  
> +	case PCI_EXP_LNKCTL: {
> +		/* u32 contains both PCI_EXP_LNKCTL and PCI_EXP_LNKSTA */
> +		u32 val = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg) &
> +			~(PCI_EXP_LNKSTA_LT << 16);
> +		if (!advk_pcie_link_up(pcie))
> +			val |= (PCI_EXP_LNKSTA_LT << 16);
> +		*value = val;
> +		return PCI_BRIDGE_EMUL_HANDLED;
> +	}
> +
>  	case PCI_CAP_LIST_ID:
>  	case PCI_EXP_DEVCAP:
>  	case PCI_EXP_DEVCTL:
>  	case PCI_EXP_LNKCAP:
> -	case PCI_EXP_LNKCTL:
>  		*value = advk_readl(pcie, PCIE_CORE_PCIEXP_CAP + reg);
>  		return PCI_BRIDGE_EMUL_HANDLED;
>  	default:
> @@ -447,8 +469,13 @@ advk_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
>  
>  	switch (reg) {
>  	case PCI_EXP_DEVCTL:
> +		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> +		break;
> +
>  	case PCI_EXP_LNKCTL:
>  		advk_writel(pcie, new, PCIE_CORE_PCIEXP_CAP + reg);
> +		if (new & PCI_EXP_LNKCTL_RL)
> +			advk_pcie_wait_for_retrain(pcie);
>  		break;
>  
>  	case PCI_EXP_RTCTL:
> -- 
> 2.20.1
>