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* [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
@ 2021-08-23 15:49 Bjorn Andersson
  2021-08-23 15:49 ` [PATCH v2 2/2] PCI: qcom: Add sc8180x compatible Bjorn Andersson
                   ` (3 more replies)
  0 siblings, 4 replies; 11+ messages in thread
From: Bjorn Andersson @ 2021-08-23 15:49 UTC (permalink / raw)
  To: Bjorn Helgaas, Rob Herring, Jingoo Han, Gustavo Pimentel,
	Lorenzo Pieralisi, Krzysztof Wilczyński, Stanimir Varbanov
  Cc: linux-arm-msm, linux-pci, devicetree, linux-kernel

On the Qualcomm sc8180x platform the bootloader does something related
to PCI that leaves a pending "msi" interrupt, which with the current
ordering often fires before init has a chance to enable the clocks that
are necessary for the interrupt handler to access the hardware.

Move the host_init() call before the registration of the "msi" interrupt
handler to ensure the host driver has a chance to enable the clocks.

The assignment of the bridge's ops and child_ops is moved along, because
at least the TI Keystone driver overwrites these in its host_init
callback.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---

Changes since v1:
- New patch, instead of enabling resources in the qcom driver before jumping to
  dw_pcie_host_init(), per Rob Herring's suggestion.

 .../pci/controller/dwc/pcie-designware-host.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index d1d9b8344ec9..f4755f3a03be 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -335,6 +335,16 @@ int dw_pcie_host_init(struct pcie_port *pp)
 	if (pci->link_gen < 1)
 		pci->link_gen = of_pci_get_max_link_speed(np);
 
+	/* Set default bus ops */
+	bridge->ops = &dw_pcie_ops;
+	bridge->child_ops = &dw_child_pcie_ops;
+
+	if (pp->ops->host_init) {
+		ret = pp->ops->host_init(pp);
+		if (ret)
+			return ret;
+	}
+
 	if (pci_msi_enabled()) {
 		pp->has_msi_ctrl = !(pp->ops->msi_host_init ||
 				     of_property_read_bool(np, "msi-parent") ||
@@ -388,15 +398,6 @@ int dw_pcie_host_init(struct pcie_port *pp)
 		}
 	}
 
-	/* Set default bus ops */
-	bridge->ops = &dw_pcie_ops;
-	bridge->child_ops = &dw_child_pcie_ops;
-
-	if (pp->ops->host_init) {
-		ret = pp->ops->host_init(pp);
-		if (ret)
-			goto err_free_msi;
-	}
 	dw_pcie_iatu_detect(pci);
 
 	dw_pcie_setup_rc(pp);
-- 
2.29.2


^ permalink raw reply	[flat|nested] 11+ messages in thread

* [PATCH v2 2/2] PCI: qcom: Add sc8180x compatible
  2021-08-23 15:49 [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Bjorn Andersson
@ 2021-08-23 15:49 ` Bjorn Andersson
  2021-08-23 17:47   ` Rob Herring
  2021-08-23 17:46 ` [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Rob Herring
                   ` (2 subsequent siblings)
  3 siblings, 1 reply; 11+ messages in thread
From: Bjorn Andersson @ 2021-08-23 15:49 UTC (permalink / raw)
  To: Bjorn Helgaas, Rob Herring, Jingoo Han, Gustavo Pimentel,
	Lorenzo Pieralisi, Krzysztof Wilczyński, Stanimir Varbanov
  Cc: linux-arm-msm, linux-pci, devicetree, linux-kernel

The SC8180x platform comes with 4 PCIe controllers, typically used for
things such as NVME storage or connecting a SDX55 5G modem. Add a
compatible for this, that just reuses the 1.9.0 ops.

Link: https://lore.kernel.org/linux-arm-msm/20210725040038.3966348-4-bjorn.andersson@linaro.org/
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---

Changes since v1:
- None

 Documentation/devicetree/bindings/pci/qcom,pcie.txt | 5 +++--
 drivers/pci/controller/dwc/pcie-qcom.c              | 1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/pci/qcom,pcie.txt b/Documentation/devicetree/bindings/pci/qcom,pcie.txt
index 3f646875f8c2..a0ae024c2d0c 100644
--- a/Documentation/devicetree/bindings/pci/qcom,pcie.txt
+++ b/Documentation/devicetree/bindings/pci/qcom,pcie.txt
@@ -12,6 +12,7 @@
 			- "qcom,pcie-ipq4019" for ipq4019
 			- "qcom,pcie-ipq8074" for ipq8074
 			- "qcom,pcie-qcs404" for qcs404
+			- "qcom,pcie-sc8180x" for sc8180x
 			- "qcom,pcie-sdm845" for sdm845
 			- "qcom,pcie-sm8250" for sm8250
 			- "qcom,pcie-ipq6018" for ipq6018
@@ -156,7 +157,7 @@
 			- "pipe"	PIPE clock
 
 - clock-names:
-	Usage: required for sm8250
+	Usage: required for sc8180x and sm8250
 	Value type: <stringlist>
 	Definition: Should contain the following entries
 			- "aux"		Auxiliary clock
@@ -245,7 +246,7 @@
 			- "ahb"			AHB reset
 
 - reset-names:
-	Usage: required for sdm845 and sm8250
+	Usage: required for sc8180x, sdm845 and sm8250
 	Value type: <stringlist>
 	Definition: Should contain the following entries
 			- "pci"			PCIe core reset
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 8a7a300163e5..f3d9e522cfab 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1554,6 +1554,7 @@ static const struct of_device_id qcom_pcie_match[] = {
 	{ .compatible = "qcom,pcie-ipq4019", .data = &ops_2_4_0 },
 	{ .compatible = "qcom,pcie-qcs404", .data = &ops_2_4_0 },
 	{ .compatible = "qcom,pcie-sdm845", .data = &ops_2_7_0 },
+	{ .compatible = "qcom,pcie-sc8180x", .data = &ops_1_9_0 },
 	{ .compatible = "qcom,pcie-sm8250", .data = &ops_1_9_0 },
 	{ }
 };
-- 
2.29.2


^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
  2021-08-23 15:49 [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Bjorn Andersson
  2021-08-23 15:49 ` [PATCH v2 2/2] PCI: qcom: Add sc8180x compatible Bjorn Andersson
@ 2021-08-23 17:46 ` Rob Herring
  2021-08-24 19:05 ` Bjorn Helgaas
  2021-10-12 12:47 ` Lorenzo Pieralisi
  3 siblings, 0 replies; 11+ messages in thread
From: Rob Herring @ 2021-08-23 17:46 UTC (permalink / raw)
  To: Bjorn Andersson
  Cc: Bjorn Helgaas, Jingoo Han, Gustavo Pimentel, Lorenzo Pieralisi,
	Krzysztof Wilczyński, Stanimir Varbanov, linux-arm-msm,
	linux-pci, devicetree, linux-kernel

On Mon, Aug 23, 2021 at 08:49:57AM -0700, Bjorn Andersson wrote:
> On the Qualcomm sc8180x platform the bootloader does something related
> to PCI that leaves a pending "msi" interrupt, which with the current
> ordering often fires before init has a chance to enable the clocks that
> are necessary for the interrupt handler to access the hardware.
> 
> Move the host_init() call before the registration of the "msi" interrupt
> handler to ensure the host driver has a chance to enable the clocks.
> 
> The assignment of the bridge's ops and child_ops is moved along, because
> at least the TI Keystone driver overwrites these in its host_init
> callback.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
> 
> Changes since v1:
> - New patch, instead of enabling resources in the qcom driver before jumping to
>   dw_pcie_host_init(), per Rob Herring's suggestion.
> 
>  .../pci/controller/dwc/pcie-designware-host.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)

Reviewed-by: Rob Herring <robh@kernel.org>

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 2/2] PCI: qcom: Add sc8180x compatible
  2021-08-23 15:49 ` [PATCH v2 2/2] PCI: qcom: Add sc8180x compatible Bjorn Andersson
@ 2021-08-23 17:47   ` Rob Herring
  0 siblings, 0 replies; 11+ messages in thread
From: Rob Herring @ 2021-08-23 17:47 UTC (permalink / raw)
  To: Bjorn Andersson
  Cc: linux-kernel, Lorenzo Pieralisi, Bjorn Helgaas,
	Krzysztof Wilczyński, linux-pci, devicetree, Rob Herring,
	Stanimir Varbanov, Gustavo Pimentel, Jingoo Han, linux-arm-msm

On Mon, 23 Aug 2021 08:49:58 -0700, Bjorn Andersson wrote:
> The SC8180x platform comes with 4 PCIe controllers, typically used for
> things such as NVME storage or connecting a SDX55 5G modem. Add a
> compatible for this, that just reuses the 1.9.0 ops.
> 
> Link: https://lore.kernel.org/linux-arm-msm/20210725040038.3966348-4-bjorn.andersson@linaro.org/
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
> 
> Changes since v1:
> - None
> 
>  Documentation/devicetree/bindings/pci/qcom,pcie.txt | 5 +++--
>  drivers/pci/controller/dwc/pcie-qcom.c              | 1 +
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 

Reviewed-by: Rob Herring <robh@kernel.org>

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
  2021-08-23 15:49 [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Bjorn Andersson
  2021-08-23 15:49 ` [PATCH v2 2/2] PCI: qcom: Add sc8180x compatible Bjorn Andersson
  2021-08-23 17:46 ` [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Rob Herring
@ 2021-08-24 19:05 ` Bjorn Helgaas
  2021-08-24 20:15   ` Bjorn Andersson
  2021-10-12 12:47 ` Lorenzo Pieralisi
  3 siblings, 1 reply; 11+ messages in thread
From: Bjorn Helgaas @ 2021-08-24 19:05 UTC (permalink / raw)
  To: Bjorn Andersson
  Cc: Bjorn Helgaas, Rob Herring, Jingoo Han, Gustavo Pimentel,
	Lorenzo Pieralisi, Krzysztof Wilczyński, Stanimir Varbanov,
	linux-arm-msm, linux-pci, devicetree, linux-kernel

On Mon, Aug 23, 2021 at 08:49:57AM -0700, Bjorn Andersson wrote:
> On the Qualcomm sc8180x platform the bootloader does something related
> to PCI that leaves a pending "msi" interrupt, which with the current
> ordering often fires before init has a chance to enable the clocks that
> are necessary for the interrupt handler to access the hardware.
> 
> Move the host_init() call before the registration of the "msi" interrupt
> handler to ensure the host driver has a chance to enable the clocks.

Did you audit other drivers for similar issues?  If they do, we should
fix them all at once.

> The assignment of the bridge's ops and child_ops is moved along, because
> at least the TI Keystone driver overwrites these in its host_init
> callback.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
> 
> Changes since v1:
> - New patch, instead of enabling resources in the qcom driver before jumping to
>   dw_pcie_host_init(), per Rob Herring's suggestion.
> 
>  .../pci/controller/dwc/pcie-designware-host.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index d1d9b8344ec9..f4755f3a03be 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -335,6 +335,16 @@ int dw_pcie_host_init(struct pcie_port *pp)
>  	if (pci->link_gen < 1)
>  		pci->link_gen = of_pci_get_max_link_speed(np);
>  
> +	/* Set default bus ops */
> +	bridge->ops = &dw_pcie_ops;
> +	bridge->child_ops = &dw_child_pcie_ops;
> +
> +	if (pp->ops->host_init) {
> +		ret = pp->ops->host_init(pp);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	if (pci_msi_enabled()) {
>  		pp->has_msi_ctrl = !(pp->ops->msi_host_init ||
>  				     of_property_read_bool(np, "msi-parent") ||
> @@ -388,15 +398,6 @@ int dw_pcie_host_init(struct pcie_port *pp)
>  		}
>  	}
>  
> -	/* Set default bus ops */
> -	bridge->ops = &dw_pcie_ops;
> -	bridge->child_ops = &dw_child_pcie_ops;
> -
> -	if (pp->ops->host_init) {
> -		ret = pp->ops->host_init(pp);
> -		if (ret)
> -			goto err_free_msi;
> -	}
>  	dw_pcie_iatu_detect(pci);
>  
>  	dw_pcie_setup_rc(pp);
> -- 
> 2.29.2
> 

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
  2021-08-24 19:05 ` Bjorn Helgaas
@ 2021-08-24 20:15   ` Bjorn Andersson
  2021-08-24 20:29     ` Bjorn Helgaas
  0 siblings, 1 reply; 11+ messages in thread
From: Bjorn Andersson @ 2021-08-24 20:15 UTC (permalink / raw)
  To: Bjorn Helgaas
  Cc: Bjorn Helgaas, Rob Herring, Jingoo Han, Gustavo Pimentel,
	Lorenzo Pieralisi, Krzysztof Wilczy??ski, Stanimir Varbanov,
	linux-arm-msm, linux-pci, devicetree, linux-kernel

On Tue 24 Aug 12:05 PDT 2021, Bjorn Helgaas wrote:

> On Mon, Aug 23, 2021 at 08:49:57AM -0700, Bjorn Andersson wrote:
> > On the Qualcomm sc8180x platform the bootloader does something related
> > to PCI that leaves a pending "msi" interrupt, which with the current
> > ordering often fires before init has a chance to enable the clocks that
> > are necessary for the interrupt handler to access the hardware.
> > 
> > Move the host_init() call before the registration of the "msi" interrupt
> > handler to ensure the host driver has a chance to enable the clocks.
> 
> Did you audit other drivers for similar issues?  If they do, we should
> fix them all at once.
> 

I only looked at the DesignWware drivers, in an attempt to find any
issues the proposed reordering.

The set of bugs causes by drivers registering interrupts before critical
resources tends to be rather visible and I don't know if there's much
value in speculatively "fixing" drivers.

E.g. a quick look through the drivers I see a similar pattern in
pci-tegra.c, but it's unlikely that they have the similar problem in
practice and I have no way to validate that a change to the order would
have a positive effect - or any side effects.


Or am I misunderstanding your request?

Regards,
Bjorn

> > The assignment of the bridge's ops and child_ops is moved along, because
> > at least the TI Keystone driver overwrites these in its host_init
> > callback.
> > 
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> > ---
> > 
> > Changes since v1:
> > - New patch, instead of enabling resources in the qcom driver before jumping to
> >   dw_pcie_host_init(), per Rob Herring's suggestion.
> > 
> >  .../pci/controller/dwc/pcie-designware-host.c | 19 ++++++++++---------
> >  1 file changed, 10 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> > index d1d9b8344ec9..f4755f3a03be 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > @@ -335,6 +335,16 @@ int dw_pcie_host_init(struct pcie_port *pp)
> >  	if (pci->link_gen < 1)
> >  		pci->link_gen = of_pci_get_max_link_speed(np);
> >  
> > +	/* Set default bus ops */
> > +	bridge->ops = &dw_pcie_ops;
> > +	bridge->child_ops = &dw_child_pcie_ops;
> > +
> > +	if (pp->ops->host_init) {
> > +		ret = pp->ops->host_init(pp);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> >  	if (pci_msi_enabled()) {
> >  		pp->has_msi_ctrl = !(pp->ops->msi_host_init ||
> >  				     of_property_read_bool(np, "msi-parent") ||
> > @@ -388,15 +398,6 @@ int dw_pcie_host_init(struct pcie_port *pp)
> >  		}
> >  	}
> >  
> > -	/* Set default bus ops */
> > -	bridge->ops = &dw_pcie_ops;
> > -	bridge->child_ops = &dw_child_pcie_ops;
> > -
> > -	if (pp->ops->host_init) {
> > -		ret = pp->ops->host_init(pp);
> > -		if (ret)
> > -			goto err_free_msi;
> > -	}
> >  	dw_pcie_iatu_detect(pci);
> >  
> >  	dw_pcie_setup_rc(pp);
> > -- 
> > 2.29.2
> > 

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
  2021-08-24 20:15   ` Bjorn Andersson
@ 2021-08-24 20:29     ` Bjorn Helgaas
  2021-08-24 21:23       ` Bjorn Andersson
  0 siblings, 1 reply; 11+ messages in thread
From: Bjorn Helgaas @ 2021-08-24 20:29 UTC (permalink / raw)
  To: Bjorn Andersson
  Cc: Bjorn Helgaas, Rob Herring, Jingoo Han, Gustavo Pimentel,
	Lorenzo Pieralisi, Krzysztof Wilczy??ski, Stanimir Varbanov,
	linux-arm-msm, linux-pci, devicetree, linux-kernel

On Tue, Aug 24, 2021 at 01:15:49PM -0700, Bjorn Andersson wrote:
> On Tue 24 Aug 12:05 PDT 2021, Bjorn Helgaas wrote:
> 
> > On Mon, Aug 23, 2021 at 08:49:57AM -0700, Bjorn Andersson wrote:
> > > On the Qualcomm sc8180x platform the bootloader does something related
> > > to PCI that leaves a pending "msi" interrupt, which with the current
> > > ordering often fires before init has a chance to enable the clocks that
> > > are necessary for the interrupt handler to access the hardware.
> > > 
> > > Move the host_init() call before the registration of the "msi" interrupt
> > > handler to ensure the host driver has a chance to enable the clocks.
> > 
> > Did you audit other drivers for similar issues?  If they do, we should
> > fix them all at once.
> 
> I only looked at the DesignWware drivers, in an attempt to find any
> issues the proposed reordering.
> 
> The set of bugs causes by drivers registering interrupts before critical
> resources tends to be rather visible and I don't know if there's much
> value in speculatively "fixing" drivers.
> 
> E.g. a quick look through the drivers I see a similar pattern in
> pci-tegra.c, but it's unlikely that they have the similar problem in
> practice and I have no way to validate that a change to the order would
> have a positive effect - or any side effects.
> 
> Or am I misunderstanding your request?

That is exactly my request.  I'm not sure if the potential issue you
noticed in pci-tegra.c is similar to the one I mentioned here:

  https://lore.kernel.org/linux-pci/20210624224040.GA3567297@bjorn-Precision-5520/

but I am actually in favor of speculatively fixing drivers even though
they're hard to test.  Code like this tends to get copied to other
places, and fixing several drivers sometimes exposes opportunities for
refactoring and sharing code.

Bjorn

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
  2021-08-24 20:29     ` Bjorn Helgaas
@ 2021-08-24 21:23       ` Bjorn Andersson
  2021-10-08 17:48         ` Lorenzo Pieralisi
  0 siblings, 1 reply; 11+ messages in thread
From: Bjorn Andersson @ 2021-08-24 21:23 UTC (permalink / raw)
  To: Bjorn Helgaas
  Cc: Bjorn Helgaas, Rob Herring, Jingoo Han, Gustavo Pimentel,
	Lorenzo Pieralisi, Krzysztof Wilczy??ski, Stanimir Varbanov,
	linux-arm-msm, linux-pci, devicetree, linux-kernel

On Tue 24 Aug 13:29 PDT 2021, Bjorn Helgaas wrote:

> On Tue, Aug 24, 2021 at 01:15:49PM -0700, Bjorn Andersson wrote:
> > On Tue 24 Aug 12:05 PDT 2021, Bjorn Helgaas wrote:
> > 
> > > On Mon, Aug 23, 2021 at 08:49:57AM -0700, Bjorn Andersson wrote:
> > > > On the Qualcomm sc8180x platform the bootloader does something related
> > > > to PCI that leaves a pending "msi" interrupt, which with the current
> > > > ordering often fires before init has a chance to enable the clocks that
> > > > are necessary for the interrupt handler to access the hardware.
> > > > 
> > > > Move the host_init() call before the registration of the "msi" interrupt
> > > > handler to ensure the host driver has a chance to enable the clocks.
> > > 
> > > Did you audit other drivers for similar issues?  If they do, we should
> > > fix them all at once.
> > 
> > I only looked at the DesignWware drivers, in an attempt to find any
> > issues the proposed reordering.
> > 
> > The set of bugs causes by drivers registering interrupts before critical
> > resources tends to be rather visible and I don't know if there's much
> > value in speculatively "fixing" drivers.
> > 
> > E.g. a quick look through the drivers I see a similar pattern in
> > pci-tegra.c, but it's unlikely that they have the similar problem in
> > practice and I have no way to validate that a change to the order would
> > have a positive effect - or any side effects.
> > 
> > Or am I misunderstanding your request?
> 
> That is exactly my request.

Okay.

> I'm not sure if the potential issue you
> noticed in pci-tegra.c is similar to the one I mentioned here:
> 
>   https://lore.kernel.org/linux-pci/20210624224040.GA3567297@bjorn-Precision-5520/
> 

As I still have the tegra driver open, I share your concern about the
use of potentially uninitialized variables.

The problem I was concerned about was however the same as in my patch
and the rockchip one, that if the tegra hardware isn't clocked the
pm_runtime_get_sync() (which would turn on power and clock) happens
after setting up the msi chain handler...

> but I am actually in favor of speculatively fixing drivers even though
> they're hard to test.  Code like this tends to get copied to other
> places, and fixing several drivers sometimes exposes opportunities for
> refactoring and sharing code.
> 

Looking through the other cases mentioned in your reply above certainly
gives a feeling that this problem has been inherited from driver to
driver...

I've added a ticket to my backlog to take a deeper look at this.

Regards,
Bjorn

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
  2021-08-24 21:23       ` Bjorn Andersson
@ 2021-10-08 17:48         ` Lorenzo Pieralisi
  2021-10-08 19:08           ` Bjorn Andersson
  0 siblings, 1 reply; 11+ messages in thread
From: Lorenzo Pieralisi @ 2021-10-08 17:48 UTC (permalink / raw)
  To: Bjorn Andersson
  Cc: Bjorn Helgaas, Bjorn Helgaas, Rob Herring, Jingoo Han,
	Gustavo Pimentel, Krzysztof Wilczy??ski, Stanimir Varbanov,
	linux-arm-msm, linux-pci, devicetree, linux-kernel, vidyas

[+Vidya]

On Tue, Aug 24, 2021 at 02:23:14PM -0700, Bjorn Andersson wrote:
> On Tue 24 Aug 13:29 PDT 2021, Bjorn Helgaas wrote:
> 
> > On Tue, Aug 24, 2021 at 01:15:49PM -0700, Bjorn Andersson wrote:
> > > On Tue 24 Aug 12:05 PDT 2021, Bjorn Helgaas wrote:
> > > 
> > > > On Mon, Aug 23, 2021 at 08:49:57AM -0700, Bjorn Andersson wrote:
> > > > > On the Qualcomm sc8180x platform the bootloader does something related
> > > > > to PCI that leaves a pending "msi" interrupt, which with the current
> > > > > ordering often fires before init has a chance to enable the clocks that
> > > > > are necessary for the interrupt handler to access the hardware.
> > > > > 
> > > > > Move the host_init() call before the registration of the "msi" interrupt
> > > > > handler to ensure the host driver has a chance to enable the clocks.
> > > > 
> > > > Did you audit other drivers for similar issues?  If they do, we should
> > > > fix them all at once.
> > > 
> > > I only looked at the DesignWware drivers, in an attempt to find any
> > > issues the proposed reordering.
> > > 
> > > The set of bugs causes by drivers registering interrupts before critical
> > > resources tends to be rather visible and I don't know if there's much
> > > value in speculatively "fixing" drivers.
> > > 
> > > E.g. a quick look through the drivers I see a similar pattern in
> > > pci-tegra.c, but it's unlikely that they have the similar problem in
> > > practice and I have no way to validate that a change to the order would
> > > have a positive effect - or any side effects.
> > > 
> > > Or am I misunderstanding your request?
> > 
> > That is exactly my request.
> 
> Okay.
> 
> > I'm not sure if the potential issue you
> > noticed in pci-tegra.c is similar to the one I mentioned here:
> > 
> >   https://lore.kernel.org/linux-pci/20210624224040.GA3567297@bjorn-Precision-5520/
> > 
> 
> As I still have the tegra driver open, I share your concern about the
> use of potentially uninitialized variables.
> 
> The problem I was concerned about was however the same as in my patch
> and the rockchip one, that if the tegra hardware isn't clocked the
> pm_runtime_get_sync() (which would turn on power and clock) happens
> after setting up the msi chain handler...
> 
> > but I am actually in favor of speculatively fixing drivers even though
> > they're hard to test.  Code like this tends to get copied to other
> > places, and fixing several drivers sometimes exposes opportunities for
> > refactoring and sharing code.
> > 
> 
> Looking through the other cases mentioned in your reply above certainly
> gives a feeling that this problem has been inherited from driver to
> driver...
> 
> I've added a ticket to my backlog to take a deeper look at this.

Vidya, can you look into this please ? In the meantime I would merge
this series.

Thanks,
Lorenzo

> 
> Regards,
> Bjorn

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
  2021-10-08 17:48         ` Lorenzo Pieralisi
@ 2021-10-08 19:08           ` Bjorn Andersson
  0 siblings, 0 replies; 11+ messages in thread
From: Bjorn Andersson @ 2021-10-08 19:08 UTC (permalink / raw)
  To: Lorenzo Pieralisi
  Cc: Bjorn Helgaas, Bjorn Helgaas, Rob Herring, Jingoo Han,
	Gustavo Pimentel, Krzysztof Wilczy??ski, Stanimir Varbanov,
	linux-arm-msm, linux-pci, devicetree, linux-kernel, vidyas

On Fri 08 Oct 10:48 PDT 2021, Lorenzo Pieralisi wrote:

> [+Vidya]
> 
> On Tue, Aug 24, 2021 at 02:23:14PM -0700, Bjorn Andersson wrote:
> > On Tue 24 Aug 13:29 PDT 2021, Bjorn Helgaas wrote:
> > 
> > > On Tue, Aug 24, 2021 at 01:15:49PM -0700, Bjorn Andersson wrote:
> > > > On Tue 24 Aug 12:05 PDT 2021, Bjorn Helgaas wrote:
> > > > 
> > > > > On Mon, Aug 23, 2021 at 08:49:57AM -0700, Bjorn Andersson wrote:
> > > > > > On the Qualcomm sc8180x platform the bootloader does something related
> > > > > > to PCI that leaves a pending "msi" interrupt, which with the current
> > > > > > ordering often fires before init has a chance to enable the clocks that
> > > > > > are necessary for the interrupt handler to access the hardware.
> > > > > > 
> > > > > > Move the host_init() call before the registration of the "msi" interrupt
> > > > > > handler to ensure the host driver has a chance to enable the clocks.
> > > > > 
> > > > > Did you audit other drivers for similar issues?  If they do, we should
> > > > > fix them all at once.
> > > > 
> > > > I only looked at the DesignWware drivers, in an attempt to find any
> > > > issues the proposed reordering.
> > > > 
> > > > The set of bugs causes by drivers registering interrupts before critical
> > > > resources tends to be rather visible and I don't know if there's much
> > > > value in speculatively "fixing" drivers.
> > > > 
> > > > E.g. a quick look through the drivers I see a similar pattern in
> > > > pci-tegra.c, but it's unlikely that they have the similar problem in
> > > > practice and I have no way to validate that a change to the order would
> > > > have a positive effect - or any side effects.
> > > > 
> > > > Or am I misunderstanding your request?
> > > 
> > > That is exactly my request.
> > 
> > Okay.
> > 
> > > I'm not sure if the potential issue you
> > > noticed in pci-tegra.c is similar to the one I mentioned here:
> > > 
> > >   https://lore.kernel.org/linux-pci/20210624224040.GA3567297@bjorn-Precision-5520/
> > > 
> > 
> > As I still have the tegra driver open, I share your concern about the
> > use of potentially uninitialized variables.
> > 
> > The problem I was concerned about was however the same as in my patch
> > and the rockchip one, that if the tegra hardware isn't clocked the
> > pm_runtime_get_sync() (which would turn on power and clock) happens
> > after setting up the msi chain handler...
> > 
> > > but I am actually in favor of speculatively fixing drivers even though
> > > they're hard to test.  Code like this tends to get copied to other
> > > places, and fixing several drivers sometimes exposes opportunities for
> > > refactoring and sharing code.
> > > 
> > 
> > Looking through the other cases mentioned in your reply above certainly
> > gives a feeling that this problem has been inherited from driver to
> > driver...
> > 
> > I've added a ticket to my backlog to take a deeper look at this.
> 
> Vidya, can you look into this please ? In the meantime I would merge
> this series.
> 

I would greatly appreciate that, as it unlocks 5G connectivity and NVME
support on my laptop. I still intend to review the items Bjorn pointed
out, but I haven't gotten there yet.

Thanks,
Bjorn

> Thanks,
> Lorenzo
> 
> > 
> > Regards,
> > Bjorn

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
  2021-08-23 15:49 [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Bjorn Andersson
                   ` (2 preceding siblings ...)
  2021-08-24 19:05 ` Bjorn Helgaas
@ 2021-10-12 12:47 ` Lorenzo Pieralisi
  3 siblings, 0 replies; 11+ messages in thread
From: Lorenzo Pieralisi @ 2021-10-12 12:47 UTC (permalink / raw)
  To: Bjorn Helgaas, Gustavo Pimentel, Stanimir Varbanov,
	Krzysztof Wilczyński, Bjorn Andersson, Jingoo Han,
	Rob Herring
  Cc: Lorenzo Pieralisi, linux-arm-msm, devicetree, linux-pci, linux-kernel

On Mon, 23 Aug 2021 08:49:57 -0700, Bjorn Andersson wrote:
> On the Qualcomm sc8180x platform the bootloader does something related
> to PCI that leaves a pending "msi" interrupt, which with the current
> ordering often fires before init has a chance to enable the clocks that
> are necessary for the interrupt handler to access the hardware.
> 
> Move the host_init() call before the registration of the "msi" interrupt
> handler to ensure the host driver has a chance to enable the clocks.
> 
> [...]

Applied to pci/dwc, thanks!

[1/2] PCI: dwc: Perform host_init() before registering msi
      https://git.kernel.org/lpieralisi/pci/c/7e919677bb
[2/2] PCI: qcom: Add sc8180x compatible
      https://git.kernel.org/lpieralisi/pci/c/0e00fc858f

Thanks,
Lorenzo

^ permalink raw reply	[flat|nested] 11+ messages in thread

end of thread, other threads:[~2021-10-12 12:47 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-08-23 15:49 [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Bjorn Andersson
2021-08-23 15:49 ` [PATCH v2 2/2] PCI: qcom: Add sc8180x compatible Bjorn Andersson
2021-08-23 17:47   ` Rob Herring
2021-08-23 17:46 ` [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Rob Herring
2021-08-24 19:05 ` Bjorn Helgaas
2021-08-24 20:15   ` Bjorn Andersson
2021-08-24 20:29     ` Bjorn Helgaas
2021-08-24 21:23       ` Bjorn Andersson
2021-10-08 17:48         ` Lorenzo Pieralisi
2021-10-08 19:08           ` Bjorn Andersson
2021-10-12 12:47 ` Lorenzo Pieralisi

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