linux-kernel - Re: [PATCH v3 2/4] PCI: brcmstb: Add ACPI config space quirk

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Message-ID: <44ad79081412af289c68e74cdecb6a2baa2e873c.camel@kernel.org>
Date:   Mon, 30 Aug 2021 10:36:43 +0200
From:   nicolas saenz julienne <nsaenz@...nel.org>
To:     Jeremy Linton <jeremy.linton@....com>, linux-pci@...r.kernel.org
Cc:     lorenzo.pieralisi@....com, bhelgaas@...gle.com, rjw@...ysocki.net,
        lenb@...nel.org, robh@...nel.org, kw@...ux.com,
        f.fainelli@...il.com, bcm-kernel-feedback-list@...adcom.com,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] PCI: brcmstb: Add ACPI config space quirk

Hi Jeremy,
sorry for the late reply, I've been on vacation.

On Thu, 2021-08-26 at 02:15 -0500, Jeremy Linton wrote:

[...]

> +static void __iomem *brcm_pcie_map_conf2(struct pci_bus *bus,
> +					unsigned int devfn, int where)
> +{
> +	struct pci_config_window *cfg = bus->sysdata;
> +	void __iomem *base = cfg->win;
> +	int idx;
> +	u32 up;
> +
> +	/* Accesses to the RC go right to the RC registers if slot==0 */
> +	if (pci_is_root_bus(bus))
> +		return PCI_SLOT(devfn) ? NULL : base + where;
> +
> +	/*
> +	 * Assure the link is up before sending requests downstream. This is done
> +	 * to avoid sending transactions to EPs that don't exist. Link flap
> +	 * conditions/etc make this race more probable. The resulting unrecoverable
> +	 * SERRORs will result in the machine crashing.
> +	 */
> +	up = readl(base + PCIE_MISC_PCIE_STATUS);
> +	if (!(up & PCIE_MISC_PCIE_STATUS_PCIE_DL_ACTIVE_MASK))
> +		return NULL;
> +
> +	if (!(up & PCIE_MISC_PCIE_STATUS_PCIE_PHYLINKUP_MASK))
> +		return NULL;

Couldn't this be integrated in the original brcm_pcie_map_conf()? IIUC there is
nothing ACPI specific about it. It'd also make for less code duplication.

Regards,
Nicolas