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Message-ID: <CA+-6iNy0O8WJMm+z7QOEsMpGAj=-quBmbPwrZpgxo19kVB921g@mail.gmail.com>
Date: Tue, 1 Dec 2020 15:12:54 -0500
From: Jim Quinlan <james.quinlan@...adcom.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS"
<linux-pci@...r.kernel.org>,
Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
Mark Brown <broonie@...nel.org>,
"maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE"
<bcm-kernel-feedback-list@...adcom.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Rob Herring <robh@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Florian Fainelli <f.fainelli@...il.com>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-rpi-kernel@...ts.infradead.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-arm-kernel@...ts.infradead.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/6] PCI: brcmstb: Add panic/die handler to RC driver
On Tue, Dec 1, 2020 at 1:05 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Mon, Nov 30, 2020 at 04:11:42PM -0500, Jim Quinlan wrote:
> > Whereas most PCIe HW returns 0xffffffff on illegal accesses and the like,
> > by default Broadcom's STB PCIe controller effects an abort. This simple
> > handler determines if the PCIe controller was the cause of the abort and if
> > so, prints out diagnostic info.
>
> What happens during enumeration? pci_bus_generic_read_dev_vendor_id()
> assumes a read of Vendor ID returns 0xffffffff if the device doesn't
> exist.
>
> I assume this case doesn't cause the abort you're referring to here,
> or nothing would work. I think this enumeration case results in PCIe
> Unsupported Request errors (PCIe r5.0, sec 2.3.2 implementation note).
Hi Bjorn,
Yes, our controller makes a special case to allow for config-space
accesses to the dev_id and vendor_id registers. even if the device is
missing. That being said, it will abort on any access if the link is
down.
However, the 7216-type SOCs bring PCIe error-reporting HW but also
have a mode where 0xffffffff is returned on improper accesses, just
like many other controllers. We are debating whether we should turn
this on by default.
Regards,
Jim Quinlan
Broadcom STB
>
> Bjorn
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