linux-kernel - Re: [PATCH v2 3/6] PCI: brcmstb: Add "refusal mode" to preclude PCIe-induced CPU aborts

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Message-ID: <20220720220840.GA1663326@bhelgaas>
Date:   Wed, 20 Jul 2022 17:08:40 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jim Quinlan <jim2101024@...il.com>
Cc:     linux-pci@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Cyril Brulebois <kibi@...ian.org>,
        bcm-kernel-feedback-list@...adcom.com, james.quinlan@...adcom.com,
        Florian Fainelli <f.fainelli@...il.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.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 3/6] PCI: brcmstb: Add "refusal mode" to preclude
 PCIe-induced CPU aborts

On Sat, Jul 16, 2022 at 06:24:50PM -0400, Jim Quinlan wrote:
> Our PCIe RC HW has an atypical behavior: if it does not have PCIe link
> established between itself and downstream, any subsequent config space
> access causes a CPU abort.  This commit sets a "refusal mode" if the PCIe
> link-up fails, and this has our pci_ops map_bus function returning a NULL
> address, which in turn precludes the access from happening.

> @@ -687,6 +688,19 @@ static void __iomem *brcm_pcie_map_conf(struct pci_bus *bus, unsigned int devfn,

Oh, and I forgot to mention that brcmstb is one of the few drivers
that doesn't name these functions ".*_map_bus()".  It's helpful when
they all match a simple grep pattern.  Maybe a patch at the end could
fix this.