linux-kernel - Re: [PATCH v5 3/3] PCI: Set dma-can-stall for HiSilicon chips

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Message-ID: <20210826182624.GA3694827@bjorn-Precision-5520>
Date:   Thu, 26 Aug 2021 13:26:24 -0500
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, Wangzhou <wangzhou1@...ilicon.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v5 3/3] PCI: Set dma-can-stall for HiSilicon chips

[+cc Will, Robin, Joerg, hoping for an ack]

On Tue, Jul 13, 2021 at 10:54:36AM +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>
> ---
>  drivers/pci/quirks.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 5d46ac6..03b0f98 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -1823,10 +1823,23 @@ 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"),

"dma-can-stall" is used in arm_smmu_probe_device() to help set
master->stall_enabled.

I don't know the implications, so it'd be nice to get an ack from a
maintainer of that code.

> +		{},
> +	};
> +
>  	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");
>  }
>  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
>