PCI: 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 "pci=ecrc=<policy>" command-line
option. If this option is not set or is set to 'bios", the enable and
generation bits are left in whatever state that firmware/BIOS set them to.
The "off" setting turns them off, and the "on" option turns them on (if the
device supports it).

Turning ECRC on or off can be a data integrity versus performance
tradeoff.  In theory, turning it on will catch more data errors, turning
it off means possibly better performance since CRC does not need to be
calculated by the PCIe hardware and packet sizes are reduced.

Signed-off-by: Andrew Patterson <andrew.patterson@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

4 files changed, 155 insertions, 7 deletions

diff --git a/drivers/pci/pcie/aer/Kconfig b/drivers/pci/pcie/aer/Kconfig
index c3bde588aa13..db4cb950933a 100644
--- a/drivers/pci/pcie/aer/Kconfig
+++ b/drivers/pci/pcie/aer/Kconfig
@@ -10,3 +10,16 @@ config PCIEAER
 	  This enables PCI Express Root Port Advanced Error Reporting
 	  (AER) driver support. Error reporting messages sent to Root
 	  Port will be handled by PCI Express AER driver.
+
+
+#
+# PCI Express ECRC
+#
+config PCIE_ECRC
+	bool "PCI Express ECRC settings control"
+	depends on PCIEAER
+	help
+	  Used to override firmware/bios settings for PCI Express ECRC
+	  (transaction layer end-to-end CRC checking).
+
+	  When in doubt, say N.
diff --git a/drivers/pci/pcie/aer/Makefile b/drivers/pci/pcie/aer/Makefile
index 8da3bd8455a8..7f93411c56e5 100644
--- a/drivers/pci/pcie/aer/Makefile
+++ b/drivers/pci/pcie/aer/Makefile
@@ -4,6 +4,8 @@
 
 obj-$(CONFIG_PCIEAER) += aerdriver.o
 
+obj-$(CONFIG_PCIE_ECRC)	+= ecrc.o
+
 aerdriver-objs := aerdrv_errprint.o aerdrv_core.o aerdrv.o
 aerdriver-$(CONFIG_ACPI) += aerdrv_acpi.o
 
diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
index 307452f30035..dd3829e68e3f 100644
--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/drivers/pci/pcie/aer/aerdrv_core.c
@@ -113,15 +113,17 @@ static void set_device_error_reporting(struct pci_dev *dev, void *data)
 {
 	bool enable = *((bool *)data);
 
-	if (dev->pcie_type != PCIE_RC_PORT &&
-	    dev->pcie_type != PCIE_SW_UPSTREAM_PORT &&
-	    dev->pcie_type != PCIE_SW_DOWNSTREAM_PORT)
-		return;
+	if (dev->pcie_type == PCIE_RC_PORT ||
+	    dev->pcie_type == PCIE_SW_UPSTREAM_PORT ||
+	    dev->pcie_type == PCIE_SW_DOWNSTREAM_PORT) {
+		if (enable)
+			pci_enable_pcie_error_reporting(dev);
+		else
+			pci_disable_pcie_error_reporting(dev);
+	}
 
 	if (enable)
-		pci_enable_pcie_error_reporting(dev);
-	else
-		pci_disable_pcie_error_reporting(dev);
+		pcie_set_ecrc_checking(dev);
 }
 
 /**
diff --git a/drivers/pci/pcie/aer/ecrc.c b/drivers/pci/pcie/aer/ecrc.c
new file mode 100644
index 000000000000..ece97df4df6d
--- /dev/null
+++ b/drivers/pci/pcie/aer/ecrc.c
@@ -0,0 +1,131 @@
+/*
+ *    Enables/disables PCIe ECRC checking.
+ *
+ *    (C) Copyright 2009 Hewlett-Packard Development Company, L.P.
+ *    Andrew Patterson <andrew.patterson@hp.com>
+ *
+ *    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 for performance */
+#define ECRC_POLICY_ON      2		/* ECRC on for data integrity */
+
+static int ecrc_policy = ECRC_POLICY_DEFAULT;
+
+static const char *ecrc_policy_str[] = {
+	[ECRC_POLICY_DEFAULT] = "bios",
+	[ECRC_POLICY_OFF] = "off",
+	[ECRC_POLICY_ON] = "on"
+};
+
+/**
+ * enable_ercr_checking - enable PCIe ECRC checking for a device
+ * @dev: the PCI device
+ *
+ * Returns 0 on success, or negative on failure.
+ */
+static int enable_ecrc_checking(struct pci_dev *dev)
+{
+	int pos;
+	u32 reg32;
+
+	if (!dev->is_pcie)
+		return -ENODEV;
+
+	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 (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;
+}
+
+/**
+ * disable_ercr_checking - disables PCIe ECRC checking for a device
+ * @dev: the PCI device
+ *
+ * Returns 0 on success, or negative on failure.
+ */
+static int disable_ecrc_checking(struct pci_dev *dev)
+{
+	int pos;
+	u32 reg32;
+
+	if (!dev->is_pcie)
+		return -ENODEV;
+
+	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);
+	reg32 &= ~(PCI_ERR_CAP_ECRC_GENE | PCI_ERR_CAP_ECRC_CHKE);
+	pci_write_config_dword(dev, pos + PCI_ERR_CAP, reg32);
+
+	return 0;
+}
+
+/**
+ * pcie_set_ecrc_checking - set/unset PCIe ECRC checking for a device based on global policy
+ * @dev: the PCI device
+ */
+void pcie_set_ecrc_checking(struct pci_dev *dev)
+{
+	switch (ecrc_policy) {
+	case ECRC_POLICY_DEFAULT:
+		return;
+	case ECRC_POLICY_OFF:
+		disable_ecrc_checking(dev);
+		break;
+	case ECRC_POLICY_ON:
+		enable_ecrc_checking(dev);;
+		break;
+	default:
+		return;
+	}
+}
+
+/**
+ * pcie_ecrc_get_policy - parse kernel command-line ecrc option
+ */
+void 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;
+
+	ecrc_policy = i;
+}