[PATCH-RFC] drivers: pci: pcieport: Allow AER service only on root ports

[PATCH-RFC] drivers: pci: pcieport: Allow AER service only on root ports

[Daniel Walker]

From: Suneel Garapati <sgarapati@marvell.com>

Some AER interrupt capability registers may not be present on
non Root ports. Since there is no way to check presence of
ROOT_ERR_COMMAND and ROOT_ERR_STATUS registers. Allow AER
service only on root ports.
Otherwise AER interrupt message number is read incorrectly
causing MSIX vector registration to fail and fallback to legacy
unnecessarily.

Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
Reviewed-by: Chandrakala Chavva <cchavva@marvell.com>
Reviewed-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
---
 drivers/pci/pcie/portdrv_core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 3ee63968deaa..edc355971a32 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -221,7 +221,16 @@ static int get_port_device_capability(struct pci_dev *dev)
 	}
 
 #ifdef CONFIG_PCIEAER
+	/*
+	 * Some AER interrupt capability registers may not be present on
+	 * non Root ports. Since there is no way to check presence of
+	 * ROOT_ERR_COMMAND and ROOT_ERR_STATUS registers. Allow AER
+	 * service only on root ports. Refer PCIe rev5.0 spec v1.0 7.8.4.
+	 * Otherwise AER interrupt message number is read incorrectly
+	 * causing MSIX vector registration to fail and fallback to legacy.
+	 */
 	if (dev->aer_cap && pci_aer_available() &&
+	    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT &&
 	    (pcie_ports_native || host->native_aer)) {
 		services |= PCIE_PORT_SERVICE_AER;
 
-- 
2.25.1

Re: [PATCH-RFC] drivers: pci: pcieport: Allow AER service only on root ports

[Bjorn Helgaas]

Please note "git log --oneline drivers/pci/pcie/portdrv_core.c" and
make your patch follow the style.

On Thu, Oct 07, 2021 at 12:44:09PM -0700, Daniel Walker wrote:
> From: Suneel Garapati <sgarapati@marvell.com>
> 
> Some AER interrupt capability registers may not be present on
> non Root ports. Since there is no way to check presence of
> ROOT_ERR_COMMAND and ROOT_ERR_STATUS registers. Allow AER
> service only on root ports.
> Otherwise AER interrupt message number is read incorrectly
> causing MSIX vector registration to fail and fallback to legacy
> unnecessarily.

Wrap to fill 75 columns.

Add blank lines between paragraphs.

Use complete sentences ("Since there is ..." is not a sentence).

Capitalize consistently ("Root ports" vs "root ports").

Use register names I can find in the spec or with grep
("ROOT_ERR_COMMAND" and "ROOT_ERR_STATUS" do not appear in the
source).

s/MSIX/MSI-X/ to match spec usage.

Also applies to code comment below.

> Signed-off-by: Suneel Garapati <sgarapati@marvell.com>

Needs to include your (Daniel's) Signed-off-by; see:

  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=v5.14#n365

> Reviewed-by: Chandrakala Chavva <cchavva@marvell.com>
> Reviewed-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
> ---
>  drivers/pci/pcie/portdrv_core.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 3ee63968deaa..edc355971a32 100644
> --- a/drivers/pci/pcie/portdrv_core.c
> +++ b/drivers/pci/pcie/portdrv_core.c
> @@ -221,7 +221,16 @@ static int get_port_device_capability(struct pci_dev *dev)
>  	}
>  
>  #ifdef CONFIG_PCIEAER
> +	/*
> +	 * Some AER interrupt capability registers may not be present on
> +	 * non Root ports. Since there is no way to check presence of
> +	 * ROOT_ERR_COMMAND and ROOT_ERR_STATUS registers. Allow AER
> +	 * service only on root ports. Refer PCIe rev5.0 spec v1.0 7.8.4.

Sec 7.8.4 talks about Root Ports and Root Complex Event Collectors
together, so I would think you would treat them the same here.

> +	 * Otherwise AER interrupt message number is read incorrectly
> +	 * causing MSIX vector registration to fail and fallback to legacy.
> +	 */
>  	if (dev->aer_cap && pci_aer_available() &&
> +	    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT &&
>  	    (pcie_ports_native || host->native_aer)) {
>  		services |= PCIE_PORT_SERVICE_AER;
>  
> -- 
> 2.25.1
>