linux-kernel - Re: [PATCH v2 3/3] PCI: set dma-can-stall for HiSilicon chip

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Message-ID: <20210121165706.GA2663152@bjorn-Precision-5520>
Date:   Thu, 21 Jan 2021 10:57:06 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Zhangfei Gao <zhangfei.gao@...aro.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        jean-philippe <jean-philippe@...aro.org>,
        kenneth-lee-2012@...mail.com, wangzhou1@...ilicon.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] PCI: set dma-can-stall for HiSilicon chip

On Mon, Jan 18, 2021 at 04:58:36PM +0800, Zhangfei Gao wrote:
> HiSilicon KunPeng920 and KunPeng930 have devices appear as PCI but are
> actually on the AMBA bus. These fake PCI devices can support SVA via
> SMMU stall feature, by setting dma-can-stall for ACPI platforms.
> 
> Signed-off-by: Zhangfei Gao <zhangfei.gao@...aro.org>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
> Signed-off-by: Zhou Wang <wangzhou1@...ilicon.com>
> ---
> Property dma-can-stall depends on patchset
> https://lore.kernel.org/linux-iommu/20210108145217.2254447-1-jean-philippe@linaro.org/
> 
>  drivers/pci/quirks.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 873d27f..b866cdf 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -1827,10 +1827,23 @@ DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_HUAWEI, 0x1610, PCI_CLASS_BRIDGE_PCI
>  
>  static void quirk_huawei_pcie_sva(struct pci_dev *pdev)
>  {
> +	struct property_entry properties[] = {
> +		PROPERTY_ENTRY_BOOL("dma-can-stall"),
> +		{},
> +	};
> +
>  	if (pdev->revision != 0x21 && pdev->revision != 0x30)
>  		return;
>  
>  	pdev->pasid_no_tlp = 1;
> +
> +	/*
> +	 * Set the dma-can-stall property on ACPI platforms. Device tree
> +	 * can set it directly.
> +	 */
> +	if (!pdev->dev.of_node &&
> +	    device_add_properties(&pdev->dev, properties))
> +		pci_warn(pdev, "could not add stall property");

What's the purpose of adding the "dma-can-stall" property?  I don't
see any reference to that property in the tree or in this series.  If
this is related to some other series that uses it, perhaps this part
should be moved to that series?

>  }
>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa250, quirk_huawei_pcie_sva);
>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa251, quirk_huawei_pcie_sva);
> -- 
> 2.7.4
>