linux-kernel - Re: [RFC PATCH v1] PCI: qcom: Use quirk to override incorrect device class

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Message-ID: <38ad143b-3b07-4d19-8ccd-ca39fb51e53d@free.fr>
Date:   Tue, 12 Mar 2019 18:34:55 +0100
From:   Marc Gonzalez <marc.w.gonzalez@...e.fr>
To:     Stanimir Varbanov <svarbanov@...sol.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        PCI <linux-pci@...r.kernel.org>,
        MSM <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jeffrey Hugo <jhugo@...eaurora.org>
Subject: Re: [RFC PATCH v1] PCI: qcom: Use quirk to override incorrect device
 class

On 12/03/2019 18:18, Marc Gonzalez wrote:

> On 12/03/2019 13:42, Stanimir Varbanov wrote:
> 
>> I wonder, in case that dw_pcie_setup_rc() already has a write to
>> PCI_CLASS_DEVICE configuration register to set it as a bridge do we
>> still need to do the above fixup?
> 
> I don't know, I don't have an affected device. Unless the msm8998 /is/ affected,
> and dw_pcie_setup_rc() actually fixes it?

I think you hit the nail on the head...

If I comment out
//dw_pcie_wr_own_conf(pp, PCI_CLASS_DEVICE, 2, PCI_CLASS_BRIDGE_PCI);
from dw_pcie_setup_rc()
then pci_class() returns 0xff000000 instead of 0x6040000

So perhaps you're right: the quirk can be omitted altogether.
Unless it is not possible to program the device class on older chips?

Regards.