[PATCH] Add support for turning PCIe ECRC on or off

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Add support for turning PCIe ECRC on or off

Adds support for PCI Express transaction layer end-to-end CRC checking
(ECRC).  This patch will enable/disable ECRC checking by setting/clearing
the ECRC Check Enable and/or ECRC Generation Enable bits for devices that
support ECRC.

The ECRC setting is controlled by the "pcie_ecrc=" command-line option. If
this option is not set or is set to 'default", the enable and generation
bits are left in whatever state that firmware/BIOS sets them to.  The
"off" setting turns them off, and the "on" option turns them on (if the
device supports it).

Signed-off-by: Andrew Patterson <andrew.patterson@xxxxxx>
---

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1754fed..c346b55 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1776,6 +1776,12 @@ and is between 256 and 4096 characters. It is defined in the file
 		force	Enable ASPM even on devices that claim not to support it.
 			WARNING: Forcing ASPM on may cause system lockups.
 
+	pcie_ecrc=	[PCI] Enable/disable PCIe ECRC (transaction layer
+			end-to-end CRC checking).
+			pcie_ecrc=default: Use BIOS/firmware settings.
+			pcie_ecrc=off: Turn ECRC off
+			pcie_ecrc=on: Turn ECRC on.
+
 	pcmv=		[HW,PCMCIA] BadgePAD 4
 
 	pd.		[PARIDE]
diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
index 5a0c6ad..d90f831 100644
--- a/drivers/pci/pcie/Kconfig
+++ b/drivers/pci/pcie/Kconfig
@@ -46,3 +46,15 @@ config PCIEASPM_DEBUG
 	help
 	  This enables PCI Express ASPM debug support. It will add per-device
 	  interface to control ASPM.
+
+#
+# PCI Express ECRC
+#
+config PCIEECRC
+	bool "PCI Express ECRC support"
+	depends on PCI
+	help
+	  Enables PCI Express ECRC (transaction layer end-to-end CRC
+	  checking)
+
+	  When in doubt, say N.
diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
index 11f6bb1..acef212 100644
--- a/drivers/pci/pcie/Makefile
+++ b/drivers/pci/pcie/Makefile
@@ -5,6 +5,9 @@
 # Build PCI Express ASPM if needed
 obj-$(CONFIG_PCIEASPM)		+= aspm.o
 
+# Build PCI Express ECRC if needed
+obj-$(CONFIG_PCIEECRC)		+= ecrc.o
+
 pcieportdrv-y			:= portdrv_core.o portdrv_pci.o portdrv_bus.o
 
 obj-$(CONFIG_PCIEPORTBUS)	+= pcieportdrv.o
diff --git a/drivers/pci/pcie/ecrc.c b/drivers/pci/pcie/ecrc.c
new file mode 100644
index 0000000..eeb93df
--- /dev/null
+++ b/drivers/pci/pcie/ecrc.c
@@ -0,0 +1,94 @@
+/*
+ *    Enables/disables PCIe ECRC checking.
+ *
+ *    (C) Copyright 20009 Hewlett-Packard Development Company, L.P.
+ *    Andrew Patterson <andrew.patterson@xxxxxx>
+ *
+ *    This program is free software; you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation; version 2 of the License.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ *    General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program; if not, write to the Free Software
+ *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ *    02111-1307, USA.
+ *
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/pci.h>
+#include <linux/pci_regs.h>
+#include <linux/errno.h>
+#include "../pci.h"
+
+#define ECRC_POLICY_DEFAULT 0		/* ECRC set by BIOS */
+#define ECRC_POLICY_OFF     1		/* ECRC off */
+#define ECRC_POLICY_ON      2		/* ECRC on */
+
+static int ecrc_policy = ECRC_POLICY_DEFAULT;
+
+static const char *ecrc_policy_str[] = {
+	[ECRC_POLICY_DEFAULT] = "default",
+	[ECRC_POLICY_OFF] = "off",
+	[ECRC_POLICY_ON] = "on"
+};
+
+/**
+ * pcie_set_ercr_checking - enable/disable PCIe ECRC checking
+ * @dev: the PCI device
+ *
+ * Returns 0 on success, or negative on failure.
+ */
+int pcie_set_ecrc_checking(struct pci_dev *dev)
+{
+	int pos;
+	u32 reg32;
+
+	if (!dev->is_pcie)
+		return -ENODEV;
+
+	/* Use firmware/BIOS setting if default */
+	if (ecrc_policy == ECRC_POLICY_DEFAULT)
+		return 0;
+
+	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
+	if (!pos)
+		return -ENODEV;
+
+	pci_read_config_dword(dev, pos + PCI_ERR_CAP, &reg32);
+	if (ecrc_policy == ECRC_POLICY_OFF) {
+		reg32 &= ~(PCI_ERR_CAP_ECRC_GENE | PCI_ERR_CAP_ECRC_CHKE);
+	} else if (ecrc_policy == ECRC_POLICY_ON) {
+		if (reg32 & PCI_ERR_CAP_ECRC_GENC)
+			reg32 |= PCI_ERR_CAP_ECRC_GENE;
+		if (reg32 & PCI_ERR_CAP_ECRC_CHKC)
+			reg32 |= PCI_ERR_CAP_ECRC_CHKE;
+	}
+	pci_write_config_dword(dev, pos + PCI_ERR_CAP, reg32);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pcie_set_ecrc_checking);
+
+static int __init pcie_ecrc_get_policy(char *str)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ecrc_policy_str); i++)
+		if (!strncmp(str, ecrc_policy_str[i],
+			     strlen(ecrc_policy_str[i])))
+			break;
+	if (i >= ARRAY_SIZE(ecrc_policy_str))
+		return 0;
+
+	ecrc_policy = i;
+	return 1;
+}
+__setup("pcie_ecrc=", pcie_ecrc_get_policy);
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index e2f3dd0..e2b0ab5 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -984,6 +984,9 @@ static void pci_init_capabilities(struct pci_dev *dev)
 
 	/* Single Root I/O Virtualization */
 	pci_iov_init(dev);
+
+	/* PCIe ECRC */
+	pcie_set_ecrc_checking(dev);
 }
 
 void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 507552d..080afd8 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -879,6 +879,15 @@ static inline int pcie_aspm_enabled(void)
 extern int pcie_aspm_enabled(void);
 #endif
 
+#ifndef CONFIG_PCIEECRC
+static inline int pcie_set_ecrc_checking(struct pci_dev *dev)
+{
+	return 0;
+}
+#else
+extern int pcie_set_ecrc_checking(struct pci_dev *dev);
+#endif
+
 #define pci_enable_msi(pdev)	pci_enable_msi_block(pdev, 1)
 
 #ifdef CONFIG_HT_IRQ

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