[v3,1/2] i2c_imc: New driver for Intel's iMC, found on LGA2011 SNB chips
diff mbox

Message ID 2d85852187abaf55c1675e30e82aef52c5c9c9e2.1461891499.git.luto@kernel.org
State New
Headers show

Commit Message

Andy Lutomirski April 29, 2016, 1:03 a.m. UTC
Sandy Bridge Xeon and Extreme chips have integrated memory
controllers with (rather limited) onboard SMBUS masters.  This
driver gives access to the bus.

There were various groups working on standardizing a way to arbitrate
access to the bus between the OS, SMM firmware, a BMC, hardware
thermal control, etc.  In the mean time, running this driver is unsafe
except under special circumstances.  Nonetheless, this driver has real
use deployed use cases: there are many Sandy Bridge systems with
pre-NFIT ADR NVDIMMs installed, and many of these NVDIMMs are designed
to be programmed over SMBUS.

As a compromise, the driver will refuse to load unless
i2c_imc.allow_unsafe_access=Y.  When safe access becomes available, we
can leave this option as a way for legacy users to run the driver, and
we'll allow the driver to load by default if safe bus access is
available.

This driver currently only supports SNB.  It should be straightforward
to extend it to all newer CPUs, but I don't have the hardware to test
it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/i2c/busses/Kconfig   |  18 ++
 drivers/i2c/busses/Makefile  |   1 +
 drivers/i2c/busses/i2c-imc.c | 567 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 586 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-imc.c

Patch
diff mbox

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index faa8e6821fea..3c05de897566 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -152,6 +152,24 @@  config I2C_ISMT
 	  This driver can also be built as a module.  If so, the module will be
 	  called i2c-ismt.
 
+config I2C_IMC
+	tristate "Intel iMC (LGA 2011) SMBus Controller"
+	depends on PCI && X86
+	help
+	  If you say yes to this option, support will be included for the Intel
+	  Integrated Memory Controller SMBus host controller interface.  This
+	  controller is found on LGA 2011 Sandy Bridge Xeons and Core i7
+	  Extremes.
+
+	  There are currently no systems on which the kernel knows that it can
+	  safely enable this driver.  For now, you need to pass this driver a
+	  scary module parameter, and you should only pass that parameter if you
+	  have a special motherboard and know exactly what you are doing.
+	  Special motherboards include the Supermicro X9DRH-iF-NV.
+
+	  This driver can also be built as a module.  If so, the module will be
+	  called i2c-imc.
+
 config I2C_PIIX4
 	tristate "Intel PIIX4 and compatible (ATI/AMD/Serverworks/Broadcom/SMSC)"
 	depends on PCI
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 37f2819b4560..ab3cdf1b3ca1 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -15,6 +15,7 @@  obj-$(CONFIG_I2C_AMD8111)	+= i2c-amd8111.o
 obj-$(CONFIG_I2C_I801)		+= i2c-i801.o
 obj-$(CONFIG_I2C_ISCH)		+= i2c-isch.o
 obj-$(CONFIG_I2C_ISMT)		+= i2c-ismt.o
+obj-$(CONFIG_I2C_IMC)		+= i2c-imc.o
 obj-$(CONFIG_I2C_NFORCE2)	+= i2c-nforce2.o
 obj-$(CONFIG_I2C_NFORCE2_S4985)	+= i2c-nforce2-s4985.o
 obj-$(CONFIG_I2C_PIIX4)		+= i2c-piix4.o
diff --git a/drivers/i2c/busses/i2c-imc.c b/drivers/i2c/busses/i2c-imc.c
new file mode 100644
index 000000000000..ace93bb1adb2
--- /dev/null
+++ b/drivers/i2c/busses/i2c-imc.c
@@ -0,0 +1,567 @@ 
+/*
+ * Copyright (c) 2013-2016 Andrew Lutomirski <luto@amacapital.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/pci.h>
+#include <linux/ratelimit.h>
+#include <linux/i2c.h>
+
+/*
+ * The datasheet can be found here, for example:
+ * http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/xeon-e5-1600-2600-vol-2-datasheet.pdf
+ *
+ * There seem to be quite a few bugs or spec errors, though:
+ *
+ *  - A successful transaction sets WOD and RDO.
+ *
+ *  - The docs for TSOD_POLL_EN make no sense (see imc_channel_claim).
+ *
+ *  - Erratum BT109, which says:
+ *
+ *      The processor may not complete SMBus (System Management Bus)
+ *      transactions targeting the TSOD (Temperature Sensor On DIMM)
+ *      when Package C-States are enabled. Due to this erratum, if the
+ *      processor transitions into a Package C-State while an SMBus
+ *      transaction with the TSOD is in process, the processor will
+ *      suspend receipt of the transaction. The transaction completes
+ *      while the processor is in a Package C-State.  Upon exiting
+ *      Package C-State, the processor will attempt to resume the
+ *      SMBus transaction, detect a protocol violation, and log an
+ *      error.
+ *
+ *   The description notwithstanding, I've seen difficult-to-reproduce
+ *   issues when the system goes completely idle (so package C-states can
+ *   be entered) while software-initiated SMBUS transactions are in
+ *   progress.
+ */
+
+/* Register offsets (in PCI configuration space) */
+#define SMBSTAT(i)			(0x180 + 0x10*(i))
+#define SMBCMD(i)			(0x184 + 0x10*(i))
+#define SMBCNTL(i)			(0x188 + 0x10*(i))
+#define SMB_TSOD_POLL_RATE_CNTR(i)	(0x18C + 0x10*(i))
+#define SMB_TSOD_POLL_RATE		(0x1A8)
+
+/* SMBSTAT fields */
+#define SMBSTAT_RDO		(1U << 31)	/* Read Data Valid */
+#define SMBSTAT_WOD		(1U << 30)	/* Write Operation Done */
+#define SMBSTAT_SBE		(1U << 29)	/* SMBus Error */
+#define SMBSTAT_SMB_BUSY	(1U << 28)	/* SMBus Busy State */
+/* 26:24 is the last automatically polled TSOD address */
+#define SMBSTAT_RDATA_MASK	0xffff		/* result of a read */
+
+/* SMBCMD fields */
+#define SMBCMD_TRIGGER		(1U << 31)	/* CMD Trigger */
+#define SMBCMD_PNTR_SEL		(1U << 30)	/* HW polls TSOD with pointer */
+#define SMBCMD_WORD_ACCESS	(1U << 29)	/* word (vs byte) access */
+#define SMBCMD_TYPE_MASK	(3U << 27)	/* Mask for access type */
+#define  SMBCMD_TYPE_READ	(0U << 27)	/* Read */
+#define  SMBCMD_TYPE_WRITE	(1U << 27)	/* Write */
+#define  SMBCMD_TYPE_PNTR_WRITE	(3U << 27)	/* Write to pointer */
+#define SMBCMD_SA_MASK		(7U << 24)	/* Slave Address high bits */
+#define SMBCMD_SA_SHIFT		24
+#define SMBCMD_BA_MASK		0xff0000	/* Bus Txn address */
+#define SMBCMD_BA_SHIFT		16
+#define SMBCMD_WDATA_MASK	0xffff		/* data to write */
+
+/* SMBCNTL fields */
+#define SMBCNTL_DTI_MASK	0xf0000000	/* Slave Address low bits */
+#define SMBCNTL_DTI_SHIFT	28		/* Slave Address low bits */
+#define SMBCNTL_CKOVRD		(1U << 27)	/* # Clock Override */
+#define SMBCNTL_DIS_WRT		(1U << 26)	/* Disable Write (sadly) */
+#define SMBCNTL_SOFT_RST	(1U << 10)	/* Soft Reset */
+#define SMBCNTL_TSOD_POLL_EN	(1U << 8)	/* TSOD Polling Enable */
+/* Bits 0-3 and 4-6 indicate TSOD presence in various slots */
+
+/* Bits that might randomly change if we race with something. */
+#define SMBCMD_OUR_BITS		(~(u32)SMBCMD_TRIGGER)
+#define SMBCNTL_OUR_BITS	(SMBCNTL_DTI_MASK | SMBCNTL_TSOD_POLL_EN)
+
+/* System Address Controller, PCI dev 13 fn 6, 8086.3cf5 */
+#define SAD_CONTROL 0xf4
+
+#define PCI_DEVICE_ID_INTEL_SBRIDGE_BR          0x3cf5  /* 13.6 */
+#define PCI_DEVICE_ID_INTEL_SBRIDGE_IMC_TA      0x3ca8  /* 15.0 */
+
+static atomic_t imc_raced;  /* Set permanently to 1 if we screw up. */
+
+static bool allow_unsafe_access;
+
+struct imc_channel {
+	struct i2c_adapter adapter;
+	struct mutex mutex;  /* protects access to regs and prev_tsod_poll */
+	bool can_write, suspended;
+	bool prev_tsod_poll;
+};
+
+struct imc_priv {
+	struct pci_dev *pci_dev;
+	struct imc_channel channels[2];
+};
+
+static bool imc_wait_not_busy(struct imc_priv *priv, int chan, u32 *stat)
+{
+	/*
+	 * The clock is around 100kHz, and transactions are nine cycles
+	 * per byte plus a few start/stop cycles, plus whatever clock
+	 * streching is involved.  This means that polling every 70us
+	 * or so will give decent performance.
+	 *
+	 * Ideally we would calculate a good estimate for the
+	 * transaction time and sleep, but busy-waiting is an effective
+	 * workaround for an apparent Sandy Bridge bug that causes bogus
+	 * output if the system enters a package C-state.  (NB: these
+	 * states are systemwide -- we don't need be running on the
+	 * right package for this to work.)
+	 *
+	 * When Ivy Bridge and Haswell support are added, we could
+	 * consider making the busy-wait depend on the platform.
+	 */
+
+	int i;
+
+	for (i = 0; i < 50; i++) {
+		pci_read_config_dword(priv->pci_dev, SMBSTAT(chan), stat);
+		if (!(*stat & SMBSTAT_SMB_BUSY))
+			return true;
+		udelay(70);  /* see comment above -- we need to busy-wait */
+	}
+
+	return false;
+}
+
+static void imc_channel_release(struct imc_priv *priv, int chan)
+{
+	/* Return to HW control. */
+	if (priv->channels[chan].prev_tsod_poll) {
+		u32 cntl;
+
+		pci_read_config_dword(priv->pci_dev, SMBCNTL(chan), &cntl);
+		cntl |= SMBCNTL_TSOD_POLL_EN;
+		pci_write_config_dword(priv->pci_dev, SMBCNTL(chan), cntl);
+	}
+}
+
+static int imc_channel_claim(struct imc_priv *priv, int chan)
+{
+	/*
+	 * The docs are a bit confused here.  We're supposed to disable TSOD
+	 * polling, then wait for busy to be cleared, then set
+	 * SMBCNTL_TSOD_POLL_EN to zero to switch to software control.  But
+	 * SMBCNTL_TSOD_POLL_EN is the only documented way to turn off polling.
+	 */
+
+	u32 cntl, stat;
+
+	if (priv->channels[chan].suspended)
+		return -EIO;
+
+	pci_read_config_dword(priv->pci_dev, SMBCNTL(chan), &cntl);
+	priv->channels[chan].prev_tsod_poll = !!(cntl & SMBCNTL_TSOD_POLL_EN);
+	cntl &= ~SMBCNTL_TSOD_POLL_EN;
+	pci_write_config_dword(priv->pci_dev, SMBCNTL(chan), cntl);
+
+	/* Sometimes the hardware won't let go. */
+	pci_read_config_dword(priv->pci_dev, SMBCNTL(chan), &cntl);
+	if (cntl & SMBCNTL_TSOD_POLL_EN)
+		return -EBUSY;
+
+	if (!imc_wait_not_busy(priv, chan, &stat)) {
+		imc_channel_release(priv, chan);
+		return -EBUSY;  /* Someone else is controlling the bus. */
+	}
+
+	return 0;  /* The channel is ours. */
+}
+
+static bool imc_channel_can_claim(struct imc_priv *priv, int chan)
+{
+	u32 orig_cntl, cntl;
+
+	/* See if we can turn off TSOD_POLL_EN. */
+
+	pci_read_config_dword(priv->pci_dev, SMBCNTL(chan), &orig_cntl);
+	pci_write_config_dword(priv->pci_dev, SMBCNTL(chan),
+			       orig_cntl & ~SMBCNTL_TSOD_POLL_EN);
+
+	pci_read_config_dword(priv->pci_dev, SMBCNTL(chan), &cntl);
+	if (cntl & SMBCNTL_TSOD_POLL_EN)
+		return false;  /* Failed. */
+
+	pci_write_config_dword(priv->pci_dev, SMBCNTL(chan), orig_cntl);
+	return true;
+}
+
+/*
+ * The iMC supports five access types.  The terminology is rather
+ * inconsistent.  These are the types:
+ *
+ * "Write to pointer register SMBus": I2C_SMBUS_WRITE, I2C_SMBUS_BYTE
+ *
+ * Read byte/word: I2C_SMBUS_READ, I2C_SMBUS_{BYTE|WORD}_DATA
+ *
+ * Write byte/word: I2C_SMBUS_WRITE, I2C_SMBUS_{BYTE|WORD}_DATA
+ *
+ * The pointer write operations is AFAICT completely useless for
+ * software control, for two reasons.  First, HW periodically polls any
+ * TSODs on the bus, so it will corrupt the pointer in between SW
+ * transactions.  More importantly, the matching "read byte"/"receive
+ * byte" (the address-less single-byte read) is not available for SW
+ * control.  Therefore, this driver doesn't implement pointer writes
+ *
+ * There is no PEC support.
+ */
+
+static u32 imc_func(struct i2c_adapter *adapter)
+{
+	int chan;
+	struct imc_channel *ch;
+	struct imc_priv *priv = i2c_get_adapdata(adapter);
+
+	chan = (adapter == &priv->channels[0].adapter ? 0 : 1);
+	ch = &priv->channels[chan];
+
+	if (ch->can_write)
+		return I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA;
+	else
+		return I2C_FUNC_SMBUS_READ_BYTE_DATA |
+			I2C_FUNC_SMBUS_READ_WORD_DATA;
+}
+
+static s32 imc_smbus_xfer(struct i2c_adapter *adap, u16 addr,
+			  unsigned short flags, char read_write, u8 command,
+			  int size, union i2c_smbus_data *data)
+{
+	int ret, chan;
+	u32 cmd = 0, cntl, final_cmd, final_cntl, stat;
+	struct imc_channel *ch;
+	struct imc_priv *priv = i2c_get_adapdata(adap);
+
+	if (atomic_read(&imc_raced))
+		return -EIO;  /* Minimize damage. */
+
+	chan = (adap == &priv->channels[0].adapter ? 0 : 1);
+	ch = &priv->channels[chan];
+
+	/* Encode CMD part of addresses and access size */
+	cmd |= ((u32)addr & 0x7) << SMBCMD_SA_SHIFT;
+	cmd |= ((u32)command) << SMBCMD_BA_SHIFT;
+	if (size == I2C_SMBUS_WORD_DATA)
+		cmd |= SMBCMD_WORD_ACCESS;
+
+	/* Encode read/write and data to write */
+	if (read_write == I2C_SMBUS_READ) {
+		cmd |= SMBCMD_TYPE_READ;
+	} else {
+		cmd |= SMBCMD_TYPE_WRITE;
+		cmd |= (size == I2C_SMBUS_WORD_DATA
+			    ? swab16(data->word)
+			    : data->byte);
+	}
+
+	mutex_lock(&ch->mutex);
+
+	ret = imc_channel_claim(priv, chan);
+	if (ret)
+		goto out_unlock;
+
+	pci_read_config_dword(priv->pci_dev, SMBCNTL(chan), &cntl);
+	cntl &= ~SMBCNTL_DTI_MASK;
+	cntl |= ((u32)addr >> 3) << SMBCNTL_DTI_SHIFT;
+	pci_write_config_dword(priv->pci_dev, SMBCNTL(chan), cntl);
+
+	/*
+	 * This clears SMBCMD_PNTR_SEL.  We leave it cleared so that we don't
+	 * need to think about keeping the TSOD pointer state consistent with
+	 * the hardware's expectation.  This probably has some miniscule
+	 * power cost, as TSOD polls will take 9 extra cycles.
+	 */
+	cmd |= SMBCMD_TRIGGER;
+	pci_write_config_dword(priv->pci_dev, SMBCMD(chan), cmd);
+
+	if (!imc_wait_not_busy(priv, chan, &stat)) {
+		/* Timeout.  TODO: Reset the controller? */
+		ret = -ETIMEDOUT;
+		dev_dbg(&priv->pci_dev->dev, "controller is wedged\n");
+		goto out_release;
+	}
+
+	/*
+	 * Be paranoid: try to detect races.  This will only detect races
+	 * against BIOS, not against hardware.  (I've never seen this happen.)
+	 */
+	pci_read_config_dword(priv->pci_dev, SMBCMD(chan), &final_cmd);
+	pci_read_config_dword(priv->pci_dev, SMBCNTL(chan), &final_cntl);
+	if (((cmd ^ final_cmd) & SMBCMD_OUR_BITS) ||
+	    ((cntl ^ final_cntl) & SMBCNTL_OUR_BITS)) {
+		WARN(1, "iMC SMBUS raced against firmware");
+		dev_err(&priv->pci_dev->dev,
+			"Access to channel %d raced: cmd 0x%08X->0x%08X, cntl 0x%08X->0x%08X\n",
+			chan, cmd, final_cmd, cntl, final_cntl);
+		atomic_set(&imc_raced, 1);
+		ret = -EIO;
+		goto out_release;
+	}
+
+	if (stat & SMBSTAT_SBE) {
+		/*
+		 * Clear the error to re-enable TSOD polling.  The docs say
+		 * that, as long as SBE is set, TSOD polling won't happen.
+		 * The docs also say that writing zero to this bit (which is
+		 * the only writable bit in the whole register) will clear
+		 * the error.  Empirically, writing 0 does not clear SBE, but
+		 * it's probably still good to do the write in compliance with
+		 * the spec.  (TSOD polling still happens and seems to
+		 * clear SBE on its own.)
+		 */
+		pci_write_config_dword(priv->pci_dev, SMBSTAT(chan), 0);
+		ret = -ENXIO;
+		goto out_release;
+	}
+
+	if (read_write == I2C_SMBUS_READ) {
+		if (!(stat & SMBSTAT_RDO)) {
+			dev_dbg(&priv->pci_dev->dev,
+				"Unexpected read status 0x%08X\n", stat);
+			ret = -EIO;
+			goto out_release;
+		}
+
+		/*
+		 * The iMC SMBUS controller thinks of SMBUS words as
+		 * being big-endian (MSB first).  Linux treats them as
+		 * little-endian, so we need to swap them.
+		 *
+		 * Note: the controller will often (always?) set WOD
+		 * here.  This is probably a hardware bug.
+		 */
+		if (size == I2C_SMBUS_WORD_DATA)
+			data->word = swab16(stat & SMBSTAT_RDATA_MASK);
+		else
+			data->byte = stat & 0xFF;
+	} else {
+		/*
+		 * Note: the controller will often (always?) set RDO here.
+		 * This is probably a hardware bug.
+		 */
+		if (!(stat & SMBSTAT_WOD)) {
+			dev_dbg(&priv->pci_dev->dev,
+				"Unexpected write status 0x%08X\n", stat);
+			ret = -EIO;
+		}
+	}
+
+out_release:
+	imc_channel_release(priv, chan);
+
+out_unlock:
+	mutex_unlock(&ch->mutex);
+
+	return ret;
+}
+
+static const struct i2c_algorithm imc_smbus_algorithm = {
+	.smbus_xfer	= imc_smbus_xfer,
+	.functionality	= imc_func,
+};
+
+static int imc_init_channel(struct imc_priv *priv, int i, int socket)
+{
+	int err;
+	u32 val;
+	struct imc_channel *ch = &priv->channels[i];
+
+	/*
+	 * With CLTT enabled, the hardware won't let us turn
+	 * off TSOD polling.  The device is completely useless
+	 * when this happens (at least without help from Intel),
+	 * but we can at least minimize confusion.
+	 */
+	if (!imc_channel_can_claim(priv, i)) {
+		dev_warn(&priv->pci_dev->dev,
+			 "iMC channel %d: we cannot control the HW.  Is CLTT on?\n",
+			 i);
+		return -EBUSY;
+	}
+
+	i2c_set_adapdata(&ch->adapter, priv);
+	ch->adapter.owner = THIS_MODULE;
+	ch->adapter.algo = &imc_smbus_algorithm;
+	ch->adapter.dev.parent = &priv->pci_dev->dev;
+
+	pci_read_config_dword(priv->pci_dev, SMBCNTL(i), &val);
+	ch->can_write = !(val & SMBCNTL_DIS_WRT);
+
+	mutex_init(&ch->mutex);
+
+	snprintf(ch->adapter.name, sizeof(ch->adapter.name),
+		 "iMC socket %d channel %d", socket, i);
+	err = i2c_add_adapter(&ch->adapter);
+	if (err) {
+		mutex_destroy(&ch->mutex);
+		return err;
+	}
+
+	return 0;
+}
+
+static void imc_free_channel(struct imc_priv *priv, int i)
+{
+	struct imc_channel *ch = &priv->channels[i];
+
+	i2c_del_adapter(&ch->adapter);
+	mutex_destroy(&ch->mutex);
+}
+
+static struct pci_dev *imc_get_related_device(struct pci_bus *bus,
+					      unsigned int devfn, u16 devid)
+{
+	struct pci_dev *dev = pci_get_slot(bus, devfn);
+
+	if (!dev)
+		return NULL;
+	if (dev->vendor != PCI_VENDOR_ID_INTEL || dev->device != devid) {
+		pci_dev_put(dev);
+		return NULL;
+	}
+	return dev;
+}
+
+static int imc_probe(struct pci_dev *dev, const struct pci_device_id *id)
+{
+	int i, j, err;
+	struct imc_priv *priv;
+	struct pci_dev *sad;  /* System Address Decoder */
+	u32 sad_control;
+
+	/* Paranoia: the datasheet says this is always at 15.0 */
+	if (dev->devfn != PCI_DEVFN(15, 0))
+		return -ENODEV;
+
+	/*
+	 * The socket number is hidden away on a different PCI device.
+	 * There's another copy at devfn 11.0 offset 0x40, and an even
+	 * less convincing copy at 5.0 0x140.  The actual APICID register
+	 * is "not used ... and is still implemented in hardware because
+	 * of FUD".
+	 *
+	 * In principle we could double-check that the socket matches
+	 * the numa_node from SRAT, but this is probably not worth it.
+	 */
+	sad = imc_get_related_device(dev->bus, PCI_DEVFN(13, 6),
+				     PCI_DEVICE_ID_INTEL_SBRIDGE_BR);
+	if (!sad)
+		return -ENODEV;
+	pci_read_config_dword(sad, SAD_CONTROL, &sad_control);
+	pci_dev_put(sad);
+
+	priv = devm_kzalloc(&dev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	priv->pci_dev = dev;
+
+	pci_set_drvdata(dev, priv);
+
+	for (i = 0; i < 2; i++) {
+		err = imc_init_channel(priv, i, sad_control & 0x7);
+		if (err)
+			goto exit_free_channels;
+	}
+
+	return 0;
+
+exit_free_channels:
+	for (j = 0; j < i; j++)
+		imc_free_channel(priv, j);
+	return err;
+}
+
+static void imc_remove(struct pci_dev *dev)
+{
+	int i;
+	struct imc_priv *priv = pci_get_drvdata(dev);
+
+	for (i = 0; i < 2; i++)
+		imc_free_channel(priv, i);
+}
+
+static int imc_suspend(struct pci_dev *dev, pm_message_t mesg)
+{
+	int i;
+	struct imc_priv *priv = pci_get_drvdata(dev);
+
+	/* BIOS is in charge.  We should finish any pending transaction */
+	for (i = 0; i < 2; i++) {
+		mutex_lock(&priv->channels[i].mutex);
+		priv->channels[i].suspended = true;
+		mutex_unlock(&priv->channels[i].mutex);
+	}
+
+	return 0;
+}
+
+static int imc_resume(struct pci_dev *dev)
+{
+	int i;
+	struct imc_priv *priv = pci_get_drvdata(dev);
+
+	for (i = 0; i < 2; i++) {
+		mutex_lock(&priv->channels[i].mutex);
+		priv->channels[i].suspended = false;
+		mutex_unlock(&priv->channels[i].mutex);
+	}
+
+	return 0;
+}
+
+static const struct pci_device_id imc_ids[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_SBRIDGE_IMC_TA) },
+	{ 0, }
+};
+MODULE_DEVICE_TABLE(pci, imc_ids);
+
+static struct pci_driver imc_pci_driver = {
+	.name		= "imc_smbus",
+	.id_table	= imc_ids,
+	.probe		= imc_probe,
+	.remove		= imc_remove,
+	.suspend	= imc_suspend,
+	.resume		= imc_resume,
+};
+
+static int __init i2c_imc_init(void)
+{
+	if (!allow_unsafe_access)
+		return -ENODEV;
+
+	pr_warn("using this driver is dangerous unless your firmware is specifically designed for it; use at your own risk\n");
+	return pci_register_driver(&imc_pci_driver);
+}
+module_init(i2c_imc_init);
+
+static void __exit i2c_imc_exit(void)
+{
+	pci_unregister_driver(&imc_pci_driver);
+}
+module_exit(i2c_imc_exit);
+
+module_param(allow_unsafe_access, bool, 0400);
+MODULE_PARM_DESC(allow_unsafe_access, "enable i2c_imc despite potential races against BIOS/hardware bus access");
+
+MODULE_AUTHOR("Andrew Lutomirski <luto@amacapital.net>");
+MODULE_DESCRIPTION("iMC SMBus driver");
+MODULE_LICENSE("GPL v2");