linux-kernel - Re: [PATCH INTERNAL 3/3] PCI: iproc: Disable MSI parsing in certain PAXC blocks

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Message-ID: <20180518135614.GA18605@e107981-ln.cambridge.arm.com>
Date:   Fri, 18 May 2018 14:56:14 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     poza@...eaurora.org
Cc:     Ray Jui <ray.jui@...adcom.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com, linux-pci@...r.kernel.org,
        linux-pci-owner@...r.kernel.org
Subject: Re: [PATCH INTERNAL 3/3] PCI: iproc: Disable MSI parsing in certain
 PAXC blocks

On Fri, May 18, 2018 at 02:53:41PM +0530, poza@...eaurora.org wrote:
> On 2018-05-17 22:51, Ray Jui wrote:
> >The internal MSI parsing logic in certain revisions of PAXC root
> >complexes does not work properly and can casue corruptions on the
> >writes. They need to be disabled
> >
> >Signed-off-by: Ray Jui <ray.jui@...adcom.com>
> >Reviewed-by: Scott Branden <scott.branden@...adcom.com>
> >---
> > drivers/pci/host/pcie-iproc.c | 34 ++++++++++++++++++++++++++++++++--
> > 1 file changed, 32 insertions(+), 2 deletions(-)
> >
> >diff --git a/drivers/pci/host/pcie-iproc.c b/drivers/pci/host/pcie-iproc.c
> >index 3c76c5f..b906d80 100644
> >--- a/drivers/pci/host/pcie-iproc.c
> >+++ b/drivers/pci/host/pcie-iproc.c
> >@@ -1144,10 +1144,22 @@ static int iproc_pcie_paxb_v2_msi_steer(struct
> >iproc_pcie *pcie, u64 msi_addr)
> > 	return ret;
> > }
> >
> >-static void iproc_pcie_paxc_v2_msi_steer(struct iproc_pcie *pcie, u64
> >msi_addr)
> >+static void iproc_pcie_paxc_v2_msi_steer(struct iproc_pcie *pcie, u64
> >msi_addr,
> >+					 bool enable)
> > {
> > 	u32 val;
> >
> >+	if (!enable) {
> >+		/*
> >+		 * Disable PAXC MSI steering. All write transfers will be
> >+		 * treated as non-MSI transfers
> >+		 */
> >+		val = iproc_pcie_read_reg(pcie, IPROC_PCIE_MSI_EN_CFG);
> >+		val &= ~MSI_ENABLE_CFG;
> >+		iproc_pcie_write_reg(pcie, IPROC_PCIE_MSI_EN_CFG, val);
> >+		return;
> >+	}
> >+
> > 	/*
> > 	 * Program bits [43:13] of address of GITS_TRANSLATER register into
> > 	 * bits [30:0] of the MSI base address register.  In fact, in all iProc
> >@@ -1201,7 +1213,7 @@ static int iproc_pcie_msi_steer(struct iproc_pcie
> >*pcie,
> > 			return ret;
> > 		break;
> > 	case IPROC_PCIE_PAXC_V2:
> >-		iproc_pcie_paxc_v2_msi_steer(pcie, msi_addr);
> >+		iproc_pcie_paxc_v2_msi_steer(pcie, msi_addr, true);
> 
> Are you calling iproc_pcie_paxc_v2_msi_steer() anywhere else with 'false' ?
> I see its getting called only from one place in current code
> iproc_pcie_msi_steer().

It is called below with the false field to disable MSIs. That's probably
one reason more to create a function to enable/disable MSIs instead of
adding a parameter to iproc_pcie_paxc_v2_msi_steer().

Which brings me to the question: what happens to those MSIs writes
when MSIs are disabled according to this patch ? Are they terminated
at the root complex ?

Lorenzo

> > 		break;
> > 	default:
> > 		return -EINVAL;
> >@@ -1427,6 +1439,24 @@ int iproc_pcie_remove(struct iproc_pcie *pcie)
> > }
> > EXPORT_SYMBOL(iproc_pcie_remove);
> >
> >+/*
> >+ * The MSI parsing logic in certain revisions of Broadcom PAXC based root
> >+ * complex does not work and needs to be disabled
> >+ */
> >+static void quirk_paxc_disable_msi_parsing(struct pci_dev *pdev)
> >+{
> >+	struct iproc_pcie *pcie = iproc_data(pdev->bus);
> >+
> >+	if (pdev->hdr_type == PCI_HEADER_TYPE_BRIDGE)
> >+		iproc_pcie_paxc_v2_msi_steer(pcie, 0, false);
> >+}
> >+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_BROADCOM, 0x16f0,
> >+			quirk_paxc_disable_msi_parsing);
> >+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_BROADCOM, 0xd802,
> >+			quirk_paxc_disable_msi_parsing);
> >+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_BROADCOM, 0xd804,
> >+			quirk_paxc_disable_msi_parsing);
> >+
> > MODULE_AUTHOR("Ray Jui <rjui@...adcom.com>");
> > MODULE_DESCRIPTION("Broadcom iPROC PCIe common driver");
> > MODULE_LICENSE("GPL v2");