linux-kernel - Re: [PATCH v2] PCI: Add quirk for HiSilicon NP 5896 devices

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Message-ID: <20191206181051.GA121021@google.com>
Date:   Fri, 6 Dec 2019 12:10:51 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Xiongfeng Wang <wangxiongfeng2@...wei.com>
Cc:     andrew.murray@....com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, wangkefeng.wang@...wei.com,
        huawei.libin@...wei.com, guohanjun@...wei.com
Subject: Re: [PATCH v2] PCI: Add quirk for HiSilicon NP 5896 devices

On Fri, Dec 06, 2019 at 03:01:45PM +0800, Xiongfeng Wang wrote:
> HiSilicon PCI Network Processor 5896 devices misreport the class type as
> 'NOT_DEFINED', but it is actually a network device. Also the size of
> BAR3 is reported as 265T, but this BAR is actually unused.
> This patch modify the class type to 'CLASS_NETWORK' and disable the
> unused BAR3.

"NOT_DEFINED" is not the value in the Class Code register.  The commit
message should include the actual value.

> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
> ---
>  drivers/pci/quirks.c    | 29 +++++++++++++++++++++++++++++
>  include/linux/pci_ids.h |  1 +
>  2 files changed, 30 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 4937a08..b9adebb 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5431,3 +5431,32 @@ static void quirk_reset_lenovo_thinkpad_p50_nvgpu(struct pci_dev *pdev)
>  DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, 0x13b1,
>  			      PCI_CLASS_DISPLAY_VGA, 8,
>  			      quirk_reset_lenovo_thinkpad_p50_nvgpu);
> +
> +static void quirk_hisi_fixup_np_class(struct pci_dev *pdev)
> +{
> +	u32 class = pdev->class;
> +
> +	pdev->class = PCI_BASE_CLASS_NETWORK << 8;
> +	pci_info(pdev, "PCI class overriden (%#08x -> %#08x)\n",
> +		 class, pdev->class);
> +}
> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_HUAWEI, PCI_DEVICE_ID_HISI_5896,
> +			quirk_hisi_fixup_np_class);
> +
> +/*
> + * HiSilicon NP 5896 devices BAR3 size is reported as 256T and causes problem
> + * when assigning the resources. But this BAR is actually unused by the driver,
> + * so let's disable it.

The question is not whether the BAR is used by the driver; the
question is whether the device responds to accesses to the region
described by the BAR when PCI_COMMAND_MEMORY is turned on.

> + */
> +static void quirk_hisi_fixup_np_bar(struct pci_dev *pdev)
> +{
> +	struct resource *r = &pdev->resource[3];
> +
> +	r->start = 0;
> +	r->end = 0;
> +	r->flags = 0;
> +
> +	pci_info(pdev, "Disabling invalid BAR 3\n");

This quirk clears the Linux *resource* related to the BAR, but it
does nothing with the hardware register itself.  There is no way to
disable an individual BAR; all we have is PCI_COMMAND_MEMORY, which
enables/disables all memory BARs as a group.

If this is a device defect, where the config register at 0x1c *looks*
like a BAR, but it actually isn't a BAR and doesn't cause the device
to decode any address space, a quirk like this might be OK.  But if
the device does decode address space described by that BAR, we need
more than this.

Can you provide "sudo lspci -vvxxx" output for this device?

> +}
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HUAWEI, PCI_DEVICE_ID_HISI_5896,
> +			 quirk_hisi_fixup_np_bar);
> diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
> index 2302d133..f21cd8b 100644
> --- a/include/linux/pci_ids.h
> +++ b/include/linux/pci_ids.h
> @@ -2558,6 +2558,7 @@
>  #define PCI_DEVICE_ID_KORENIX_JETCARDF3	0x17ff
>  
>  #define PCI_VENDOR_ID_HUAWEI		0x19e5
> +#define PCI_DEVICE_ID_HISI_5896        0x5896 /* HiSilicon NP 5896 devices */
>  
>  #define PCI_VENDOR_ID_NETRONOME		0x19ee
>  #define PCI_DEVICE_ID_NETRONOME_NFP4000	0x4000
> -- 
> 1.7.12.4
>