linux-kernel - Re: [PATCH 0/2] Let pci_fixup_final access iommu

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Message-ID: <20200525134318.GB5221@8bytes.org>
Date:   Mon, 25 May 2020 15:43:18 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Zhangfei Gao <zhangfei.gao@...aro.org>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Sudeep Holla <sudeep.holla@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        jean-philippe <jean-philippe@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        kenneth-lee-2012@...mail.com, Wangzhou <wangzhou1@...ilicon.com>,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-acpi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/2] Let pci_fixup_final access iommu_fwnode

On Tue, May 12, 2020 at 12:08:29PM +0800, Zhangfei Gao wrote:
> Some platform devices appear as PCI but are
> actually on the AMBA bus, and they need fixup in
> drivers/pci/quirks.c handling iommu_fwnode.
> So calling pci_fixup_final after iommu_fwnode is allocated.
> 
> For example: 
> Hisilicon platform device need fixup in 
> drivers/pci/quirks.c
> 
> +static void quirk_huawei_pcie_sva(struct pci_dev *pdev)
> +{
> +	struct iommu_fwspec *fwspec;
> +
> +	pdev->eetlp_prefix_path = 1;
> +	fwspec = dev_iommu_fwspec_get(&pdev->dev);
> +	if (fwspec)
> +		fwspec->can_stall = 1;
> +}
> +
> +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);

I don't think it is a great idea to hook this into PCI_FIXUP_FINAL. The
fixup list needs to be processed for every device, which will slow down
probing.

So either we introduce something like PCI_FIXUP_IOMMU, if this is
entirely PCI specific. If it needs to be generic we need some fixup
infrastructure in the IOMMU code itself.

Regards,

	Joerg