i2c: pasemi: Set enable bit for Apple variant

Some later revisions after the original PASemi I2C controller introduce
what likely is an enable bit to the CTL register. Without setting it the
actual i2c transmission is never started.
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Acked-by: Olof Johansson <olof@lixom.net>
Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-pasemi-core.c

@@ -22,6 +22,7 @@
 #define REG_MRXFIFO	0x04
 #define REG_SMSTA	0x14
 #define REG_CTL		0x1c
+#define REG_REV		0x28
 
 /* Register defs */
 #define MTXFIFO_READ	0x00000400
@@ -37,6 +38,7 @@
 
 #define CTL_MRR		0x00000400
 #define CTL_MTR		0x00000200
+#define CTL_EN		0x00000800
 #define CTL_CLK_M	0x000000ff
 
 static inline void reg_write(struct pasemi_smbus *smbus, int reg, int val)
@@ -60,6 +62,9 @@ static void pasemi_reset(struct pasemi_smbus *smbus)
 {
 	u32 val = (CTL_MTR | CTL_MRR | (smbus->clk_div & CTL_CLK_M));
 
+	if (smbus->hw_rev >= 6)
+		val |= CTL_EN;
+
 	reg_write(smbus, REG_CTL, val);
 }
 
@@ -335,6 +340,9 @@ int pasemi_i2c_common_probe(struct pasemi_smbus *smbus)
 	/* set up the sysfs linkage to our parent device */
 	smbus->adapter.dev.parent = smbus->dev;
 
+	if (smbus->hw_rev != PASEMI_HW_REV_PCI)
+		smbus->hw_rev = reg_read(smbus, REG_REV);
+
 	pasemi_reset(smbus);
 
 	error = devm_i2c_add_adapter(smbus->dev, &smbus->adapter);

drivers/i2c/busses/i2c-pasemi-core.h

@@ -8,11 +8,14 @@
 #include <linux/io.h>
 #include <linux/kernel.h>
 
+#define PASEMI_HW_REV_PCI -1
+
 struct pasemi_smbus {
 	struct device		*dev;
 	struct i2c_adapter	 adapter;
 	void __iomem		*ioaddr;
 	unsigned int		 clk_div;
+	int			 hw_rev;
 };
 
 int pasemi_i2c_common_probe(struct pasemi_smbus *smbus);

drivers/i2c/busses/i2c-pasemi-pci.c

@@ -42,6 +42,12 @@ static int pasemi_smb_pci_probe(struct pci_dev *dev,
 	size = pci_resource_len(dev, 0);
 	smbus->clk_div = CLK_100K_DIV;
 
+	/*
+	 * The original PASemi PCI controllers don't have a register for
+	 * their HW revision.
+	 */
+	smbus->hw_rev = PASEMI_HW_REV_PCI;
+
 	if (!devm_request_region(&dev->dev, base, size,
 			    pasemi_smb_pci_driver.name))
 		return -EBUSY;