[PATCH 2/3 v2] i2c: i2c-piix4: Use the common mutex

[Zoltan Boszormenyi]

Use the common mutex from driver/usb/host/pci-quirks.c in the
i2c-piix4 driver to synchronize access to the I/O port pair
0xcd6 / 0xcd7.

At the same time, remove the request_region() call to reserve
these I/O ports, so the sp5100_tco watchdog driver can also
load. The mutex is enough to protect the I/O port accesses.
This is an old regression in Linux 4.4-rc4, caused by:

v2: Explicit extern reference for sb800_mutex

commit 2fee61d22e606fc99ade9079fda15fdee83ec33e
Author: Christian Fetzer <fetzer.ch@xxxxxxxxx>
Date:   Thu Nov 19 20:13:48 2015 +0100

    i2c: piix4: Add support for multiplexed main adapter in SB800

Signed-off-by: Zoltan Boszormenyi <zboszor@xxxxx>
---
 drivers/i2c/busses/i2c-piix4.c | 43 +++++++++++++-----------------------------
 1 file changed, 13 insertions(+), 30 deletions(-)

diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
index c21ca7b..6c56e96 100644
--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -144,10 +144,10 @@ static const struct dmi_system_id piix4_dmi_ibm[] = {
 
 /*
  * SB800 globals
- * piix4_mutex_sb800 protects piix4_port_sel_sb800 and the pair
- * of I/O ports at SB800_PIIX4_SMB_IDX.
+ * sb800_mutex in drivers/usb/host/pci-quirks.c protects
+ * piix4_port_sel_sb800 and the pair of I/O ports at SB800_PIIX4_SMB_IDX.
  */
-static DEFINE_MUTEX(piix4_mutex_sb800);
+extern struct mutex sb800_mutex;
 static u8 piix4_port_sel_sb800;
 static const char *piix4_main_port_names_sb800[PIIX4_MAX_ADAPTERS] = {
 	" port 0", " port 2", " port 3", " port 4"
@@ -157,8 +157,6 @@ static const char *piix4_aux_port_name_sb800 = " port 1";
 struct i2c_piix4_adapdata {
 	unsigned short smba;
 
-	/* SB800 */
-	bool sb800_main;
 	u8 port;		/* Port number, shifted */
 };
 
@@ -286,12 +284,12 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
 	else
 		smb_en = (aux) ? 0x28 : 0x2c;
 
-	mutex_lock(&piix4_mutex_sb800);
+	mutex_lock(&sb800_mutex);
 	outb_p(smb_en, SB800_PIIX4_SMB_IDX);
 	smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
 	outb_p(smb_en + 1, SB800_PIIX4_SMB_IDX);
 	smba_en_hi = inb_p(SB800_PIIX4_SMB_IDX + 1);
-	mutex_unlock(&piix4_mutex_sb800);
+	mutex_unlock(&sb800_mutex);
 
 	if (!smb_en) {
 		smb_en_status = smba_en_lo & 0x10;
@@ -349,13 +347,13 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
 	if (PIIX4_dev->vendor == PCI_VENDOR_ID_AMD) {
 		piix4_port_sel_sb800 = SB800_PIIX4_PORT_IDX_ALT;
 	} else {
-		mutex_lock(&piix4_mutex_sb800);
+		mutex_lock(&sb800_mutex);
 		outb_p(SB800_PIIX4_PORT_IDX_SEL, SB800_PIIX4_SMB_IDX);
 		port_sel = inb_p(SB800_PIIX4_SMB_IDX + 1);
 		piix4_port_sel_sb800 = (port_sel & 0x01) ?
 				       SB800_PIIX4_PORT_IDX_ALT :
 				       SB800_PIIX4_PORT_IDX;
-		mutex_unlock(&piix4_mutex_sb800);
+		mutex_unlock(&sb800_mutex);
 	}
 
 	dev_info(&PIIX4_dev->dev,
@@ -592,7 +590,7 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
 	u8 port;
 	int retval;
 
-	mutex_lock(&piix4_mutex_sb800);
+	mutex_lock(&sb800_mutex);
 
 	/* Request the SMBUS semaphore, avoid conflicts with the IMC */
 	smbslvcnt  = inb_p(SMBSLVCNT);
@@ -608,7 +606,7 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
 	} while (--retries);
 	/* SMBus is still owned by the IMC, we give up */
 	if (!retries) {
-		mutex_unlock(&piix4_mutex_sb800);
+		mutex_unlock(&sb800_mutex);
 		return -EBUSY;
 	}
 
@@ -628,7 +626,7 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
 	/* Release the semaphore */
 	outb_p(smbslvcnt | 0x20, SMBSLVCNT);
 
-	mutex_unlock(&piix4_mutex_sb800);
+	mutex_unlock(&sb800_mutex);
 
 	return retval;
 }
@@ -705,7 +703,6 @@ static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
 	}
 
 	adapdata->smba = smba;
-	adapdata->sb800_main = sb800_main;
 	adapdata->port = port << 1;
 
 	/* set up the sysfs linkage to our parent device */
@@ -771,29 +768,18 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	    dev->vendor == PCI_VENDOR_ID_AMD) {
 		is_sb800 = true;
 
-		if (!request_region(SB800_PIIX4_SMB_IDX, 2, "smba_idx")) {
-			dev_err(&dev->dev,
-			"SMBus base address index region 0x%x already in use!\n",
-			SB800_PIIX4_SMB_IDX);
-			return -EBUSY;
-		}
-
 		/* base address location etc changed in SB800 */
 		retval = piix4_setup_sb800(dev, id, 0);
-		if (retval < 0) {
-			release_region(SB800_PIIX4_SMB_IDX, 2);
+		if (retval < 0)
 			return retval;
-		}
 
 		/*
 		 * Try to register multiplexed main SMBus adapter,
 		 * give up if we can't
 		 */
 		retval = piix4_add_adapters_sb800(dev, retval);
-		if (retval < 0) {
-			release_region(SB800_PIIX4_SMB_IDX, 2);
+		if (retval < 0)
 			return retval;
-		}
 	} else {
 		retval = piix4_setup(dev, id);
 		if (retval < 0)
@@ -841,11 +827,8 @@ static void piix4_adap_remove(struct i2c_adapter *adap)
 
 	if (adapdata->smba) {
 		i2c_del_adapter(adap);
-		if (adapdata->port == (0 << 1)) {
+		if (adapdata->port == (0 << 1))
 			release_region(adapdata->smba, SMBIOSIZE);
-			if (adapdata->sb800_main)
-				release_region(SB800_PIIX4_SMB_IDX, 2);
-		}
 		kfree(adapdata);
 		kfree(adap);
 	}
-- 
2.9.3