linux-kernel - Re: [PATCH v2 5/6] PCI: brcmstb: Add panic/die handler to RC driver

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Message-ID: <20201201180503.GA1321042@bjorn-Precision-5520>
Date:   Tue, 1 Dec 2020 12:05:03 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jim Quinlan <james.quinlan@...adcom.com>
Cc:     linux-pci@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        broonie@...nel.org, 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 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).

Bjorn