[PATCH v2 2/2] i2c: piix4: Use request_muxed_region

Guenter Roeck
2018-02-26T20:46:53Z

Accesses to SB800_PIIX4_SMB_IDX can occur from multiple drivers.
One example for another driver is the sp5100_tco driver.

Use request_muxed_region() to ensure synchronization.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Dropped now unnecessary include of linux/mutex.h
Added error message if request_muxed_region() fails
Spell out affected driver in commit message

Note that I did not try to do a performance analysis.
Doing so seemed excessive, even more so in the context of
piix4_imc_sleep() already using request_muxed_region().

drivers/i2c/busses/i2c-piix4.c | 55 +++++++++++++++++++-----------------------
1 file changed, 25 insertions(+), 30 deletions(-)

diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
index 4c1f6aaec0fc..90946a8b9a75 100644
--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -40,7 +40,6 @@
#include <linux/dmi.h>
#include <linux/acpi.h>
#include <linux/io.h>
-#include <linux/mutex.h>

/* PIIX4 SMBus address offsets */
@@ -153,10 +152,7 @@ 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.
*/
-static DEFINE_MUTEX(piix4_mutex_sb800);
static u8 piix4_port_sel_sb800;
static u8 piix4_port_mask_sb800;
static u8 piix4_port_shift_sb800;
@@ -298,12 +294,19 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
else
smb_en = (aux) ? 0x28 : 0x2c;

- mutex_lock(&piix4_mutex_sb800);
+ if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb")) {
+ dev_err(&PIIX4_dev->dev,
+ "SMB base address index region 0x%x already in use.\n",
+ SB800_PIIX4_SMB_IDX);
+ return -EBUSY;
+ }
+
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);
+
+ release_region(SB800_PIIX4_SMB_IDX, 2);

if (!smb_en) {
smb_en_status = smba_en_lo & 0x10;
@@ -373,7 +376,12 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
break;
}
} else {
- mutex_lock(&piix4_mutex_sb800);
+ if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2,
+ "sb800_piix4_smb")) {
+ release_region(piix4_smba, SMBIOSIZE);
+ return -EBUSY;
+ }
+
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) ?
@@ -381,7 +389,7 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
SB800_PIIX4_PORT_IDX;
piix4_port_mask_sb800 = SB800_PIIX4_PORT_IDX_MASK;
piix4_port_shift_sb800 = SB800_PIIX4_PORT_IDX_SHIFT;
- mutex_unlock(&piix4_mutex_sb800);
+ release_region(SB800_PIIX4_SMB_IDX, 2);
}

dev_info(&PIIX4_dev->dev,
@@ -679,7 +687,8 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
u8 port;
int retval;

- mutex_lock(&piix4_mutex_sb800);
+ if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb"))
+ return -EBUSY;

/* Request the SMBUS semaphore, avoid conflicts with the IMC */
smbslvcnt = inb_p(SMBSLVCNT);
@@ -695,8 +704,8 @@ 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);
- return -EBUSY;
+ retval = -EBUSY;
+ goto release;
}

/*
@@ -753,8 +762,8 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
if ((size == I2C_SMBUS_BLOCK_DATA) && adapdata->notify_imc)
piix4_imc_wakeup();

- mutex_unlock(&piix4_mutex_sb800);
-
+release:
+ release_region(SB800_PIIX4_SMB_IDX, 2);
return retval;
}

@@ -899,13 +908,6 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
bool notify_imc = false;
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;
- }
-
if (dev->vendor == PCI_VENDOR_ID_AMD &&
dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS) {
u8 imc;
@@ -922,20 +924,16 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)

/* 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, notify_imc);
- if (retval < 0) {
- release_region(SB800_PIIX4_SMB_IDX, 2);
+ if (retval < 0)
return retval;
- }
} else {
retval = piix4_setup(dev, id);
if (retval < 0)
@@ -983,11 +981,8 @@ static void piix4_adap_remove(struct i2c_adapter *adap)

if (adapdata->smba) {
i2c_del_adapter(adap);
- if (adapdata->port == (0 << piix4_port_shift_sb800)) {
+ if (adapdata->port == (0 << piix4_port_shift_sb800))
release_region(adapdata->smba, SMBIOSIZE);
- if (adapdata->sb800_main)
- release_region(SB800_PIIX4_SMB_IDX, 2);
- }
kfree(adapdata);
kfree(adap);
}
--
2.7.4