linux-kernel - [PATCH] PCI: Enable SERR# forwarding for Type-1 PCI devices

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Date:   Wed, 14 Nov 2018 20:17:01 +0530
From:   Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
To:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <bhelgaas@...gle.com>, <rgummal@...inx.com>,
        Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
Subject: [PATCH] PCI: Enable SERR# forwarding for Type-1 PCI devices

As per Figure 6-3 in PCIe r4.0, sec 6.2.6, ERR_ messages
will be forwarded from the secondary interface to the primary interface,
if the SERR# Enable bit in the Bridge Control register is set.
Currently PCI_BRIDGE_CTL_SERR is being enabled only in
ACPI flow.
This patch enables PCI_BRIDGE_CTL_SERR for Type-1 PCI device.

Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
---
 drivers/pci/probe.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index b1c05b5..ed71e8e 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1841,8 +1841,6 @@ static void program_hpp_type0(struct pci_dev *dev, struct hpp_type0 *hpp)
 		pci_write_config_byte(dev, PCI_SEC_LATENCY_TIMER,
 				      hpp->latency_timer);
 		pci_read_config_word(dev, PCI_BRIDGE_CONTROL, &pci_bctl);
-		if (hpp->enable_serr)
-			pci_bctl |= PCI_BRIDGE_CTL_SERR;
 		if (hpp->enable_perr)
 			pci_bctl |= PCI_BRIDGE_CTL_PARITY;
 		pci_write_config_word(dev, PCI_BRIDGE_CONTROL, pci_bctl);
@@ -2114,6 +2112,23 @@ static void pci_configure_eetlp_prefix(struct pci_dev *dev)
 #endif
 }
 
+static void pci_configure_serr(struct pci_dev *dev)
+{
+	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
+		u16 control;
+
+		/*
+		 * A Type-1 PCI bridge will not forward ERR_ messages coming
+		 * from an endpoint if SERR# forwarding is not enabled.
+		 */
+		pci_read_config_word(dev, PCI_BRIDGE_CONTROL, &control);
+		if (!(control & PCI_BRIDGE_CTL_SERR)) {
+			control |= PCI_BRIDGE_CTL_SERR;
+			pci_write_config_word(dev, PCI_BRIDGE_CONTROL, control);
+		}
+	}
+}
+
 static void pci_configure_device(struct pci_dev *dev)
 {
 	struct hotplug_params hpp;
@@ -2124,6 +2139,7 @@ static void pci_configure_device(struct pci_dev *dev)
 	pci_configure_relaxed_ordering(dev);
 	pci_configure_ltr(dev);
 	pci_configure_eetlp_prefix(dev);
+	pci_configure_serr(dev);
 
 	memset(&hpp, 0, sizeof(hpp));
 	ret = pci_get_hp_params(dev, &hpp);
-- 
2.7.4