linux-kernel - Re: [PATCH v2] pci: loongson: Workaround MIPS firmware MRRS settings

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Date:   Sun, 6 Aug 2023 10:20:30 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     linux-pci@...r.kernel.org, bhelgaas@...gle.com
Cc:     linux-kernel@...r.kernel.org, chenhuacai@...nel.org, kw@...ux.com,
        lpieralisi@...nel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] pci: loongson: Workaround MIPS firmware MRRS settings



在 2023/7/25 14:10, Jiaxun Yang 写道:
> This is a partial revert of commit 8b3517f88ff2 ("PCI:
> loongson: Prevent LS7A MRRS increases") for MIPS based Loongson.
>
> There are many MIPS based Loongson systems in wild that
> shipped with firmware which does not set maximum MRRS properly.
>
> Limiting MRRS to 256 for all as MIPS Loongson comes with higher
> MRRS support is considered rare.
>
> Cc: stable@...r.kernel.org
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217680
> Fixes: 8b3517f88ff2 ("PCI: loongson: Prevent LS7A MRRS increases")
> Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>

Ping?
I expect this patch to go through PCI fixes tree.

Thanks
- Jiaxun

> ---
> v2: Rename quirk name to: loongson_old_mrrs_quirk
> ---
>   drivers/pci/controller/pci-loongson.c | 38 +++++++++++++++++++++++++++
>   1 file changed, 38 insertions(+)
>
> diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
> index fe0f732f6e43..d0f68b102d10 100644
> --- a/drivers/pci/controller/pci-loongson.c
> +++ b/drivers/pci/controller/pci-loongson.c
> @@ -108,6 +108,44 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
>   DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
>   			DEV_LS7A_PCIE_PORT6, loongson_mrrs_quirk);
>   
> +#ifdef CONFIG_MIPS
> +static void loongson_old_mrrs_quirk(struct pci_dev *pdev)
> +{
> +	struct pci_bus *bus = pdev->bus;
> +	struct pci_dev *bridge;
> +	static const struct pci_device_id bridge_devids[] = {
> +		{ PCI_VDEVICE(LOONGSON, DEV_LS2K_PCIE_PORT0) },
> +		{ PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT0) },
> +		{ PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT1) },
> +		{ PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT2) },
> +		{ PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT3) },
> +		{ PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT4) },
> +		{ PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT5) },
> +		{ PCI_VDEVICE(LOONGSON, DEV_LS7A_PCIE_PORT6) },
> +		{ 0, },
> +	};
> +
> +	/* look for the matching bridge */
> +	while (!pci_is_root_bus(bus)) {
> +		bridge = bus->self;
> +		bus = bus->parent;
> +		/*
> +		 * There are still some wild MIPS Loongson firmware won't
> +		 * set MRRS properly. Limiting MRRS to 256 as MIPS Loongson
> +		 * comes with higher MRRS support is considered rare.
> +		 */
> +		if (pci_match_id(bridge_devids, bridge)) {
> +			if (pcie_get_readrq(pdev) > 256) {
> +				pci_info(pdev, "limiting MRRS to 256\n");
> +				pcie_set_readrq(pdev, 256);
> +			}
> +			break;
> +		}
> +	}
> +}
> +DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, loongson_old_mrrs_quirk);
> +#endif
> +
>   static void loongson_pci_pin_quirk(struct pci_dev *pdev)
>   {
>   	pdev->pin = 1 + (PCI_FUNC(pdev->devfn) & 3);