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From: Bjorn Helgaas <helgaas@kernel.org>
To: "Kelley, Sean V" <sean.v.kelley@intel.com>
Cc: "bhelgaas@google.com" <bhelgaas@google.com>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	"xerces.zhao@gmail.com" <xerces.zhao@gmail.com>,
	"Wysocki, Rafael J" <rafael.j.wysocki@intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	"Luck, Tony" <tony.luck@intel.com>,
	"Kuppuswamy,
	Sathyanarayanan" <sathyanarayanan.kuppuswamy@intel.com>,
	"Zhuo, Qiuxu" <qiuxu.zhuo@intel.com>,
	Linux PCI <linux-pci@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Kuppuswamy Sathyanarayanan 
	<sathyanarayanan.kuppuswamy@linux.intel.com>
Subject: Re: [PATCH v12 05/15] PCI/ERR: Simplify by using pci_upstream_bridge()
Date: Thu, 3 Dec 2020 16:25:46 -0600	[thread overview]
Message-ID: <20201203222546.GA1600426@bjorn-Precision-5520> (raw)
In-Reply-To: <BA95A917-CCFA-4A21-9146-0626716CAF65@intel.com>

On Thu, Dec 03, 2020 at 06:45:00PM +0000, Kelley, Sean V wrote:
> Just confirming that when switched from dev->bus->self to
> pci_upstream_bridge() we’re okay with the NULL case:
> 
> > On Nov 20, 2020, at 4:10 PM, Sean V Kelley <sean.v.kelley@intel.com> wrote:
> > 
> > Use pci_upstream_bridge() in place of dev->bus->self.  No functional change
> > intended.
> > 
> > [bhelgaas: split to separate patch]
> > Link: https://lore.kernel.org/r/20201002184735.1229220-6-seanvk.dev@oregontracks.org
> > Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
> > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> > Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > ---
> > drivers/pci/pcie/err.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> > index db149c6ce4fb..05f61da5ed9d 100644
> > --- a/drivers/pci/pcie/err.c
> > +++ b/drivers/pci/pcie/err.c
> > @@ -159,7 +159,7 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> > 	 */
> > 	if (!(pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
> > 	      pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM))
> > -		dev = dev->bus->self;
> > +		dev = pci_upstream_bridge(dev);
> 
> The only case where pci_upstream_bridge(dev) could be NULL is if
> dev->bus is the root bus and we are being selective based on the
> type.

Yes, pci_upstream_bridge(dev) returns NULL if dev is on a root bus.
I think bus->self is NULL for root buses anyway, so I think this patch
is OK at least at this point in the series.

> Even later in this series when we actually add in RC_EC/RC_END we
> maintain the conditional checks:
> 
> https://lore.kernel.org/linux-pci/20201121001036.8560-11-sean.v.kelley@intel.com/
> 
>  pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> 
> @@ -174,10 +180,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> 
>  
>  	/*
>  	 * Error recovery runs on all subordinates of the bridge.  If the
> -	 * bridge detected the error, it is cleared at the end.
> +	 * bridge detected the error, it is cleared at the end.  For RCiEPs
> +	 * we should reset just the RCiEP itself.
> 
>  	 */
>  	if (type == PCI_EXP_TYPE_ROOT_PORT ||
> -	    type == PCI_EXP_TYPE_DOWNSTREAM)
> +	    type == PCI_EXP_TYPE_DOWNSTREAM ||
> +	    type == PCI_EXP_TYPE_RC_EC ||
> +	    type == PCI_EXP_TYPE_RC_END)
>  		bridge = dev;
>  	else
>  		bridge = pci_upstream_bridge(dev);
> 
> I believe we are okay here.

Well, I think we're at least no worse than today.  Today we keep
"bridge == dev" for Root Ports and Downstream Ports, and use
"bridge = dev->bus->self" for everything else.

After this series we keep "bridge == dev" for RCEC and RCiEPs in
addition.

I'm not sure about PCI_EXP_TYPE_PCI_BRIDGE, which is a PCIe-to-PCI
bridge.  According to the ancient "PCI Express to PCI/PCI-X Bridge
Specification" r1.0 of July 14, 2003, sec 5.23, these bridges can have
an AER Capability (with different format that I don't see mentioned
elsewhere).

But this AER Capability doesn't have the Root registers, so I assume
it would have to be below a Root Port in order to actually signal the
errors, which would mean it could not be on a root bus.

So I don't really *love* the fact that we use pci_upstream_bridge()
and rely on these assumptions that the result will not be NULL, but I
guess it's OK for now.

> > 	bus = dev->subordinate;
> > 
> > 	pci_dbg(dev, "broadcast error_detected message\n");
> > -- 
> > 2.29.2
> > 
> > 
> 

  reply	other threads:[~2020-12-03 22:26 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-21  0:10 [PATCH v12 00/15] Add RCEC handling to PCI/AER Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 01/15] AER: aer_root_reset() non-native handling Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 02/15] PCI/RCEC: Bind RCEC devices to the Root Port driver Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 03/15] PCI/RCEC: Cache RCEC capabilities in pci_init_capabilities() Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 04/15] PCI/ERR: Rename reset_link() to reset_subordinates() Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 05/15] PCI/ERR: Simplify by using pci_upstream_bridge() Sean V Kelley
2020-12-03 18:45   ` Kelley, Sean V
2020-12-03 22:25     ` Bjorn Helgaas [this message]
2020-11-21  0:10 ` [PATCH v12 06/15] PCI/ERR: Simplify by computing pci_pcie_type() once Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 07/15] PCI/ERR: Use "bridge" for clarity in pcie_do_recovery() Sean V Kelley
2020-12-02 23:18   ` Bjorn Helgaas
2020-11-21  0:10 ` [PATCH v12 08/15] PCI/ERR: Avoid negated conditional for clarity Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 09/15] PCI/ERR: Add pci_walk_bridge() to pcie_do_recovery() Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 10/15] PCI/ERR: Limit AER resets in pcie_do_recovery() Sean V Kelley
2020-11-23 23:28   ` Bjorn Helgaas
2020-11-23 23:57     ` Kelley, Sean V
2020-11-24 17:17       ` Bjorn Helgaas
2020-11-30 19:54         ` Kelley, Sean V
2020-12-01  0:25           ` Bjorn Helgaas
2020-12-01  1:09             ` Kuppuswamy, Sathyanarayanan
2020-12-01  1:13             ` Kelley, Sean V
2020-12-02 20:53             ` Kelley, Sean V
2020-12-02 21:27               ` Bjorn Helgaas
2020-12-02 22:54                 ` Kelley, Sean V
2020-11-21  0:10 ` [PATCH v12 11/15] PCI/RCEC: Add pcie_link_rcec() to associate RCiEPs Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 12/15] PCI/RCEC: Add RCiEP's linked RCEC to AER/ERR Sean V Kelley
2020-12-02 23:44   ` Bjorn Helgaas
2020-12-03  0:51     ` Kelley, Sean V
2020-12-04  0:01       ` Bjorn Helgaas
2020-12-04 17:17         ` Kelley, Sean V
2020-12-04 17:24           ` Bjorn Helgaas
2020-12-05 21:30           ` Bjorn Helgaas
2020-12-07 17:23             ` Kelley, Sean V
2020-11-21  0:10 ` [PATCH v12 13/15] PCI/AER: Add pcie_walk_rcec() to RCEC AER handling Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 14/15] PCI/PME: Add pcie_walk_rcec() to RCEC PME handling Sean V Kelley
2020-11-21  0:10 ` [PATCH v12 15/15] PCI/AER: Add RCEC AER error injection support Sean V Kelley
2020-11-21  4:26 ` [PATCH v12 00/15] Add RCEC handling to PCI/AER Bjorn Helgaas

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