[i2c] [PATCH 2 of 2] Adding an abort function to unwedge MCP51/55

[Oleg Ryjkov]

Hi Jean, hi list,

This patch is to add an abort function that will bring back the MCP51/55
controller if it was blocked by a block-read operation, in particular.
(When a slave sends a wrong byte count on a byte read, the host gets
locked up). I've only tested it on an MCP51 and MCP55. However, I'm
almost certain it will also work on MCP65, I just did not have the board
to test it on. Thus I for now the abort function will only be called
if an MCP51/55 was detected.

Signed-off-by: Oleg Ryjkov <olegr at google.com>


--- linux-2.6-untouched/drivers/i2c/busses/i2c-nforce2.c	2007-08-30 23:30:02.000000000 -0700
+++ linux-2.6/drivers/i2c/busses/i2c-nforce2.c	2007-08-30 23:45:10.000000000 -0700
@@ -62,6 +62,7 @@
 	int base;
 	int size;
 	int blockops;
+	int can_abort;
 };
 
 
@@ -83,6 +84,14 @@
 #define NVIDIA_SMB_DATA		(smbus->base + 0x04)	/* 32 data registers */
 #define NVIDIA_SMB_BCNT		(smbus->base + 0x24)	/* number of data
 							   bytes */
+#define NVIDIA_SMB_STATUS_ABRT	(smbus->base + 0x3c)	/* register used to
+							   reset controller */
+#define NVIDIA_SMB_CTRL		(smbus->base + 0x3e)	/* control register */
+
+#define NVIDIA_SMB_STATUS_ABRT_STS	0x01            /* Bit to notify that
+                                                           abort succeeded */
+#define NVIDIA_SMB_CTRL_ABORT	0x20                    /* Bit used to issue an
+                                                           abort command */
 
 #define NVIDIA_SMB_STS_DONE	0x80
 #define NVIDIA_SMB_STS_ALRM	0x40
@@ -103,6 +112,25 @@
 
 static struct pci_driver nforce2_driver;
 
+static void nforce2_abort(struct i2c_adapter * adap) {
+	struct nforce2_smbus *smbus = adap->algo_data;
+	int timeout = 0;
+	unsigned char temp;
+
+	dev_dbg(&adap->dev, "Aborting current transaction\n");
+
+	outb_p(NVIDIA_SMB_CTRL_ABORT, NVIDIA_SMB_CTRL);
+	timeout = 0;
+	do {
+		msleep(1);
+		temp = inb_p(NVIDIA_SMB_STATUS_ABRT);
+	} while ( !(temp & NVIDIA_SMB_STATUS_ABRT_STS) &&
+			(timeout++ < MAX_TIMEOUT));
+	if ((temp & NVIDIA_SMB_STATUS_ABRT_STS)==0)
+		dev_dbg(&adap->dev, "Can't reset the smbus\n");
+	outb_p(NVIDIA_SMB_STATUS_ABRT_STS, NVIDIA_SMB_STATUS_ABRT);
+}
+
 static int nforce2_check_status(struct i2c_adapter * adap) {
 	struct nforce2_smbus *smbus = adap->algo_data;
 	int timeout = 0;
@@ -115,6 +143,8 @@
 
 	if ((~temp & NVIDIA_SMB_STS_DONE) && (timeout >= MAX_TIMEOUT)) {
 		dev_dbg(&adap->dev, "SMBus Timeout (0x%02x)!\n", temp);
+		if (smbus->can_abort == 1)
+			nforce2_abort(adap);
 		return -1;
 	}
 	if ((~temp & NVIDIA_SMB_STS_DONE) || (temp & NVIDIA_SMB_STS_STATUS)) {
@@ -324,6 +354,8 @@
 	case PCI_DEVICE_ID_NVIDIA_NFORCE_MCP55_SMBUS:
 		smbuses[0].blockops = 1;
 		smbuses[1].blockops = 1;
+		smbuses[0].can_abort = 1;
+		smbuses[1].can_abort = 1;
 	}
 
 	/* SMBus adapter 1 */