Re: [PATCH v2 1/2] PCI: keystone: Set mode as RootComplex for "ti,keystone-pcie" compatible

Re: [PATCH v2 1/2] PCI: keystone: Set mode as RootComplex for "ti,keystone-pcie" compatible

[Bjorn Helgaas]

On Fri, May 24, 2024 at 04:27:13PM +0530, Siddharth Vadapalli wrote:
> From: Kishon Vijay Abraham I <kishon@ti.com>
> 
> commit 23284ad677a9 ("PCI: keystone: Add support for PCIe EP in AM654x
> Platforms") introduced configuring "enum dw_pcie_device_mode" as part of
> device data ("struct ks_pcie_of_data"). However it failed to set mode
> for "ti,keystone-pcie" compatible. Set mode as RootComplex for
> "ti,keystone-pcie" compatible here.

23284ad677a9 appeared in v5.10.  

But I guess RC support has not been broken since v5.10 because we
never used ks_pcie_rc_of_data.mode anyway?

It looks like the only use is here:

  #define DW_PCIE_VER_365A                0x3336352a
  #define DW_PCIE_VER_480A                0x3438302a

  ks_pcie_probe
  {
    ...
    mode = data->mode;
    ...
    if (dw_pcie_ver_is_ge(pci, 480A))
      ret = ks_pcie_am654_set_mode(dev, mode);
    else
      ret = ks_pcie_set_mode(dev);

so we don't even look at .mode unless the version is v4.80a or later,
and this is v3.65a?

So this is basically a cosmetic fix (but still worth doing for
readability!) and doesn't need a stable backport, right?

If so, I might amend the commit log to mention the fact that this
doesn't actually fix a functional issue.

> Fixes: 23284ad677a9 ("PCI: keystone: Add support for PCIe EP in AM654x Platforms")
> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
> ---
>  drivers/pci/controller/dwc/pci-keystone.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c
> index d3a7d14ee685..3184546ba3b6 100644
> --- a/drivers/pci/controller/dwc/pci-keystone.c
> +++ b/drivers/pci/controller/dwc/pci-keystone.c
> @@ -1064,6 +1064,7 @@ static int ks_pcie_am654_set_mode(struct device *dev,
>  
>  static const struct ks_pcie_of_data ks_pcie_rc_of_data = {
>  	.host_ops = &ks_pcie_host_ops,
> +	.mode = DW_PCIE_RC_TYPE,
>  	.version = DW_PCIE_VER_365A,
>  };
>  
> -- 
> 2.40.1
> 

Re: [PATCH v2 1/2] PCI: keystone: Set mode as RootComplex for "ti,keystone-pcie" compatible

[Siddharth Vadapalli]

On Tue, Nov 05, 2024 at 06:57:58PM -0600, Bjorn Helgaas wrote:

Hello Bjorn,

> On Fri, May 24, 2024 at 04:27:13PM +0530, Siddharth Vadapalli wrote:
> > From: Kishon Vijay Abraham I <kishon@ti.com>
> > 
> > commit 23284ad677a9 ("PCI: keystone: Add support for PCIe EP in AM654x
> > Platforms") introduced configuring "enum dw_pcie_device_mode" as part of
> > device data ("struct ks_pcie_of_data"). However it failed to set mode
> > for "ti,keystone-pcie" compatible. Set mode as RootComplex for
> > "ti,keystone-pcie" compatible here.
> 
> 23284ad677a9 appeared in v5.10.  
> 
> But I guess RC support has not been broken since v5.10 because we
> never used ks_pcie_rc_of_data.mode anyway?
> 
> It looks like the only use is here:
> 
>   #define DW_PCIE_VER_365A                0x3336352a
>   #define DW_PCIE_VER_480A                0x3438302a
> 
>   ks_pcie_probe
>   {
>     ...
>     mode = data->mode;
>     ...
>     if (dw_pcie_ver_is_ge(pci, 480A))
>       ret = ks_pcie_am654_set_mode(dev, mode);
>     else
>       ret = ks_pcie_set_mode(dev);

"mode" is used later on during probe at:

....
	switch (mode) {
	case DW_PCIE_RC_TYPE:
	...
	case DW_PCIE_EP_TYPE:
	...
	default:
		dev_err(dev, "INVALID device type %d\n", mode);
	}
....

> 
> so we don't even look at .mode unless the version is v4.80a or later,
> and this is v3.65a?
> 
> So this is basically a cosmetic fix (but still worth doing for
> readability!) and doesn't need a stable backport, right?

I suppose that "data->mode" will default to zero for v3.65a prior to
this commit, corresponding to "DW_PCIE_UNKNOWN_TYPE" rather than the
correct value of "DW_PCIE_RC_TYPE". Since I don't have an SoC with the
v3.65a version of the controller, I cannot test it out, but I presume
that the "INVALID device type 0" error will be displayed. Though the probe
will not fail since the "default" case doesn't return an error code, the
controller probably will not be functional as the configuration associated
with the "DW_PCIE_RC_TYPE" case has been skipped. Hence, I believe that
this fix should be backported.

Regards,
Siddharth.

Re: [PATCH v2 1/2] PCI: keystone: Set mode as RootComplex for "ti,keystone-pcie" compatible

[Bjorn Helgaas]

On Wed, Nov 06, 2024 at 11:36:38AM +0530, Siddharth Vadapalli wrote:
> On Tue, Nov 05, 2024 at 06:57:58PM -0600, Bjorn Helgaas wrote:
> > On Fri, May 24, 2024 at 04:27:13PM +0530, Siddharth Vadapalli wrote:
> > > From: Kishon Vijay Abraham I <kishon@ti.com>
> > > 
> > > commit 23284ad677a9 ("PCI: keystone: Add support for PCIe EP in AM654x
> > > Platforms") introduced configuring "enum dw_pcie_device_mode" as part of
> > > device data ("struct ks_pcie_of_data"). However it failed to set mode
> > > for "ti,keystone-pcie" compatible. Set mode as RootComplex for
> > > "ti,keystone-pcie" compatible here.
> > 
> > 23284ad677a9 appeared in v5.10.  
> > 
> > But I guess RC support has not been broken since v5.10 because we
> > never used ks_pcie_rc_of_data.mode anyway?
> > 
> > It looks like the only use is here:
> > 
> >   #define DW_PCIE_VER_365A                0x3336352a
> >   #define DW_PCIE_VER_480A                0x3438302a
> > 
> >   ks_pcie_probe
> >   {
> >     ...
> >     mode = data->mode;
> >     ...
> >     if (dw_pcie_ver_is_ge(pci, 480A))
> >       ret = ks_pcie_am654_set_mode(dev, mode);
> >     else
> >       ret = ks_pcie_set_mode(dev);
> 
> "mode" is used later on during probe at:
> 
> ....
> 	switch (mode) {
> 	case DW_PCIE_RC_TYPE:
> 	...
> 	case DW_PCIE_EP_TYPE:
> 	...
> 	default:
> 		dev_err(dev, "INVALID device type %d\n", mode);
> 	}
> ....

How did I miss that? :)  It is literally two lines down.

> > so we don't even look at .mode unless the version is v4.80a or later,
> > and this is v3.65a?
> > 
> > So this is basically a cosmetic fix (but still worth doing for
> > readability!) and doesn't need a stable backport, right?
> 
> I suppose that "data->mode" will default to zero for v3.65a prior to
> this commit, corresponding to "DW_PCIE_UNKNOWN_TYPE" rather than the
> correct value of "DW_PCIE_RC_TYPE". Since I don't have an SoC with the
> v3.65a version of the controller, I cannot test it out, but I presume
> that the "INVALID device type 0" error will be displayed. Though the probe
> will not fail since the "default" case doesn't return an error code, the
> controller probably will not be functional as the configuration associated
> with the "DW_PCIE_RC_TYPE" case has been skipped. Hence, I believe that
> this fix should be backported.

I guess nobody really cares too much since it's been broken for almost
four years.

But indeed, sounds like it should have a stable tag and maybe a commit
log hint about what the failure looks like.

Thanks!

Bjorn

Re: [PATCH v2 1/2] PCI: keystone: Set mode as RootComplex for "ti,keystone-pcie" compatible

[Krzysztof Wilczyński]

Hello,

[...]
> > I suppose that "data->mode" will default to zero for v3.65a prior to
> > this commit, corresponding to "DW_PCIE_UNKNOWN_TYPE" rather than the
> > correct value of "DW_PCIE_RC_TYPE". Since I don't have an SoC with the
> > v3.65a version of the controller, I cannot test it out, but I presume
> > that the "INVALID device type 0" error will be displayed. Though the probe
> > will not fail since the "default" case doesn't return an error code, the
> > controller probably will not be functional as the configuration associated
> > with the "DW_PCIE_RC_TYPE" case has been skipped. Hence, I believe that
> > this fix should be backported.
> 
> I guess nobody really cares too much since it's been broken for almost
> four years.
> 
> But indeed, sounds like it should have a stable tag and maybe a commit
> log hint about what the failure looks like.

Added Cc for stable releases.  Siddharth, let me know how to update the
commit log per Bjorn feedback, so I can do it directly on the branch.

Thank you!

	Krzysztof

Re: [PATCH v2 1/2] PCI: keystone: Set mode as RootComplex for "ti,keystone-pcie" compatible

[Siddharth Vadapalli]

On Thu, Nov 07, 2024 at 01:05:20AM +0900, Krzysztof Wilczyński wrote:

Hello Krzysztof,

> Hello,
> 
> [...]
> > > I suppose that "data->mode" will default to zero for v3.65a prior to
> > > this commit, corresponding to "DW_PCIE_UNKNOWN_TYPE" rather than the
> > > correct value of "DW_PCIE_RC_TYPE". Since I don't have an SoC with the
> > > v3.65a version of the controller, I cannot test it out, but I presume
> > > that the "INVALID device type 0" error will be displayed. Though the probe
> > > will not fail since the "default" case doesn't return an error code, the
> > > controller probably will not be functional as the configuration associated
> > > with the "DW_PCIE_RC_TYPE" case has been skipped. Hence, I believe that
> > > this fix should be backported.
> > 
> > I guess nobody really cares too much since it's been broken for almost
> > four years.
> > 
> > But indeed, sounds like it should have a stable tag and maybe a commit
> > log hint about what the failure looks like.
> 
> Added Cc for stable releases.  Siddharth, let me know how to update the
> commit log per Bjorn feedback, so I can do it directly on the branch.

The existing commit message could be replaced by the following:

------------------------------------------------------------------------
commit 23284ad677a9 ("PCI: keystone: Add support for PCIe EP in AM654x
Platforms") introduced configuring "enum dw_pcie_device_mode" as part of
device data ("struct ks_pcie_of_data"). However it failed to set the mode
for "ti,keystone-pcie" compatible.

Since the mode defaults to "DW_PCIE_UNKNOWN_TYPE", the following error
message is displayed:
	"INVALID device type 0"
for the v3.65a controller. Despite the driver probing successfully, the
controller may not be functional in the Root Complex mode of operation.

So, set the mode as Root Complex for "ti,keystone-pcie" compatible to fix
this.
------------------------------------------------------------------------

Regards,
Siddharth.

Re: [PATCH v2 1/2] PCI: keystone: Set mode as RootComplex for "ti,keystone-pcie" compatible

[Krzysztof Wilczyński]

Hello,

> > Added Cc for stable releases.  Siddharth, let me know how to update the
> > commit log per Bjorn feedback, so I can do it directly on the branch.
> 
> The existing commit message could be replaced by the following:
> 
> ------------------------------------------------------------------------
> commit 23284ad677a9 ("PCI: keystone: Add support for PCIe EP in AM654x
> Platforms") introduced configuring "enum dw_pcie_device_mode" as part of
> device data ("struct ks_pcie_of_data"). However it failed to set the mode
> for "ti,keystone-pcie" compatible.
> 
> Since the mode defaults to "DW_PCIE_UNKNOWN_TYPE", the following error
> message is displayed:
> 	"INVALID device type 0"
> for the v3.65a controller. Despite the driver probing successfully, the
> controller may not be functional in the Root Complex mode of operation.
> 
> So, set the mode as Root Complex for "ti,keystone-pcie" compatible to fix
> this.
> ------------------------------------------------------------------------

Done.  See the following:

  - https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?h=controller/keystone&id=5a938ed9481b0c06cb97aec45e722a80568256fd

Thank you!

	Krzysztof

Re: [PATCH v2 1/2] PCI: keystone: Set mode as RootComplex for "ti,keystone-pcie" compatible

[Siddharth Vadapalli]

On Fri, Nov 08, 2024 at 12:51:44AM +0900, Krzysztof Wilczyński wrote:
> Hello,
> 
> > > Added Cc for stable releases.  Siddharth, let me know how to update the
> > > commit log per Bjorn feedback, so I can do it directly on the branch.
> > 
> > The existing commit message could be replaced by the following:
> > 
> > ------------------------------------------------------------------------
> > commit 23284ad677a9 ("PCI: keystone: Add support for PCIe EP in AM654x
> > Platforms") introduced configuring "enum dw_pcie_device_mode" as part of
> > device data ("struct ks_pcie_of_data"). However it failed to set the mode
> > for "ti,keystone-pcie" compatible.
> > 
> > Since the mode defaults to "DW_PCIE_UNKNOWN_TYPE", the following error
> > message is displayed:
> > 	"INVALID device type 0"
> > for the v3.65a controller. Despite the driver probing successfully, the
> > controller may not be functional in the Root Complex mode of operation.
> > 
> > So, set the mode as Root Complex for "ti,keystone-pcie" compatible to fix
> > this.
> > ------------------------------------------------------------------------
> 
> Done.  See the following:
> 
>   - https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?h=controller/keystone&id=5a938ed9481b0c06cb97aec45e722a80568256fd

LGTM. Thank you for updating the commit message :)

Regards,
Siddharth.