linux-kernel - Re: [PATCH 1/2] PCI: Disable MSI for Freescale PCIe RC mode

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Message-ID: <20171011193737.GP25517@bhelgaas-glaptop.roam.corp.google.com>
Date:   Wed, 11 Oct 2017 14:37:37 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Zhiqiang Hou <Zhiqiang.Hou@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pci@...r.kernel.org, bhelgaas@...gle.com, roy.zang@....com,
        mingkai.hu@....com, minghuan.lian@....com
Subject: Re: [PATCH 1/2] PCI: Disable MSI for Freescale PCIe RC mode

On Fri, Sep 22, 2017 at 03:25:21PM +0800, Zhiqiang Hou wrote:
> From: Hou Zhiqiang <Zhiqiang.Hou@....com>
> 
> The Freescale PCIe controller advertises the MSI/MSI-X capability
> in both RC and Endpoint mode, but in RC mode it doesn't support
> MSI/MSI-X by it self, it can only transfer MSI/MSI-X from downstream

s/it self,/itself;/

> devices. So add this quirk to prevent use of MSI/MSI-X in RC mode.
> 
> Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@....com>
> ---
>  drivers/pci/quirks.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index a4d33619a7bb..c1063a420f0c 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4799,3 +4799,11 @@ static void quirk_no_ats(struct pci_dev *pdev)
>  /* AMD Stoney platform GPU */
>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x98e4, quirk_no_ats);
>  #endif /* CONFIG_PCI_ATS */
> +
> +/* Freescale PCIe doesn't support MSI in RC mode */
> +static void quirk_fsl_no_msi(struct pci_dev *pdev)
> +{
> +	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT)
> +		pdev->no_msi = 1;
> +}
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_FREESCALE, PCI_ANY_ID, quirk_fsl_no_msi);

This disables MSI for all Freescale root ports, past, present, and
future.  Is that really what you want?  This is a bug (the root port
shouldn't advertise MSI if it doesn't support it), and presumably it
might be fixed in some future device?

This needs an ack from Minghuan or Mingkai (based on MAINTAINERS).

Bjorn