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Subject[PATCH] i2c: piix4: Disable completely the IMC during SMBUS_BLOCK_DATA
Date
SMBUS_BLOCK_DATA transactions might fail due to a race condition with
the IMC, even when the IMC semaphore is used.

This bug has been reported and confirmed by AMD, who suggested as a
solution an IMC firmware upgrade (obtained via BIOS update) and
disabling the IMC during SMBUS_BLOCK_DATA transactions.

Even without the IMC upgrade, the smbus is much more stable with this
patch.

Tested on a Bettong-alike board.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
---
drivers/i2c/busses/i2c-piix4.c | 89 ++++++++++++++++++++++++++++++++++++++----
1 file changed, 82 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
index 0ecdb47a23ab..3b8a5eaad956 100644
--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -85,6 +85,8 @@
/* SB800 constants */
#define SB800_PIIX4_SMB_IDX 0xcd6

+#define IMC_SMB_IDX 0x3e
+
/*
* SB800 port is selected by bits 2:1 of the smb_en register (0x2c)
* or the smb_sel register (0x2e), depending on bit 0 of register 0x2f.
@@ -160,6 +162,8 @@ struct i2c_piix4_adapdata {
/* SB800 */
bool sb800_main;
u8 port; /* Port number, shifted */
+
+ bool notify_imc;
};

static int piix4_setup(struct pci_dev *PIIX4_dev,
@@ -572,6 +576,50 @@ static s32 piix4_access(struct i2c_adapter * adap, u16 addr,
return 0;
}

+static uint8_t piix4_imc_read(uint8_t idx)
+{
+ outb_p(idx, IMC_SMB_IDX);
+ return inb_p(IMC_SMB_IDX + 1);
+}
+
+static void piix4_imc_write(uint8_t idx, uint8_t value)
+{
+ outb_p(idx, IMC_SMB_IDX);
+ outb_p(value, IMC_SMB_IDX + 1);
+}
+
+int piix4_imc_sleep(void)
+{
+ int timeout = MAX_TIMEOUT;
+
+ piix4_imc_write(0x82, 0x00);
+ piix4_imc_write(0x83, 0xB4);
+ piix4_imc_write(0x80, 0x96);
+
+ while (timeout--) {
+ if (piix4_imc_read(0x82) == 0xfa)
+ return 0;
+ usleep_range(1000, 2000);
+ }
+
+ return -ETIMEDOUT;
+}
+
+void piix4_imc_wakeup(void)
+{
+ int timeout = MAX_TIMEOUT;
+
+ piix4_imc_write(0x82, 0x00);
+ piix4_imc_write(0x83, 0xB5);
+ piix4_imc_write(0x80, 0x96);
+
+ while (timeout--) {
+ if (piix4_imc_read(0x82) == 0xfa)
+ break;
+ usleep_range(1000, 2000);
+ }
+}
+
/*
* Handles access to multiple SMBus ports on the SB800.
* The port is selected by bits 2:1 of the smb_en register (0x2c).
@@ -586,7 +634,7 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
{
struct i2c_piix4_adapdata *adapdata = i2c_get_adapdata(adap);
unsigned short piix4_smba = adapdata->smba;
- int retries = MAX_TIMEOUT;
+ int retries = adapdata->notify_imc ? MAX_TIMEOUT * 2 : MAX_TIMEOUT;
int smbslvcnt;
u8 smba_en_lo;
u8 port;
@@ -612,6 +660,15 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
return -EBUSY;
}

+ /* Block data transfers require disabling the imc */
+ if ((size == I2C_SMBUS_BLOCK_DATA) && adapdata->notify_imc)
+ /* If IMC communication fails do not retry*/
+ if (piix4_imc_sleep()) {
+ dev_warn(&adap->dev,
+ "Failed to communicate with the IMC, enable it and/or upgrade your BIOS.\n");
+ adapdata->notify_imc = false;
+ }
+
outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);

@@ -628,6 +685,9 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
/* Release the semaphore */
outb_p(smbslvcnt | 0x20, SMBSLVCNT);

+ if ((size == I2C_SMBUS_BLOCK_DATA) && adapdata->notify_imc)
+ piix4_imc_wakeup();
+
mutex_unlock(&piix4_mutex_sb800);

return retval;
@@ -679,7 +739,7 @@ static struct i2c_adapter *piix4_main_adapters[PIIX4_MAX_ADAPTERS];
static struct i2c_adapter *piix4_aux_adapter;

static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
- bool sb800_main, u8 port,
+ bool sb800_main, u8 port, bool notify_imc,
const char *name, struct i2c_adapter **padap)
{
struct i2c_adapter *adap;
@@ -707,6 +767,7 @@ static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
adapdata->smba = smba;
adapdata->sb800_main = sb800_main;
adapdata->port = port << 1;
+ adapdata->notify_imc = notify_imc;

/* set up the sysfs linkage to our parent device */
adap->dev.parent = &dev->dev;
@@ -728,14 +789,15 @@ static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
return 0;
}

-static int piix4_add_adapters_sb800(struct pci_dev *dev, unsigned short smba)
+static int piix4_add_adapters_sb800(struct pci_dev *dev, unsigned short smba,
+ bool notify_imc)
{
struct i2c_piix4_adapdata *adapdata;
int port;
int retval;

for (port = 0; port < PIIX4_MAX_ADAPTERS; port++) {
- retval = piix4_add_adapter(dev, smba, true, port,
+ retval = piix4_add_adapter(dev, smba, true, port, notify_imc,
piix4_main_port_names_sb800[port],
&piix4_main_adapters[port]);
if (retval < 0)
@@ -769,6 +831,7 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
dev->device == PCI_DEVICE_ID_ATI_SBX00_SMBUS &&
dev->revision >= 0x40) ||
dev->vendor == PCI_VENDOR_ID_AMD) {
+ bool notify_imc = false;
is_sb800 = true;

if (!request_region(SB800_PIIX4_SMB_IDX, 2, "smba_idx")) {
@@ -778,6 +841,18 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
return -EBUSY;
}

+ if (dev->vendor == PCI_VENDOR_ID_AMD &&
+ dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS) {
+ if (!devm_request_region(&dev->dev, IMC_SMB_IDX, 2,
+ "kerncz_imc_idx")) {
+ dev_warn(&dev->dev,
+ "IMC base address index region 0x%x already in use!\n",
+ SB800_PIIX4_SMB_IDX);
+ } else {
+ notify_imc = true;
+ }
+ }
+
/* base address location etc changed in SB800 */
retval = piix4_setup_sb800(dev, id, 0);
if (retval < 0) {
@@ -789,7 +864,7 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
* Try to register multiplexed main SMBus adapter,
* give up if we can't
*/
- retval = piix4_add_adapters_sb800(dev, retval);
+ retval = piix4_add_adapters_sb800(dev, retval, notify_imc);
if (retval < 0) {
release_region(SB800_PIIX4_SMB_IDX, 2);
return retval;
@@ -800,7 +875,7 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
return retval;

/* Try to register main SMBus adapter, give up if we can't */
- retval = piix4_add_adapter(dev, retval, false, 0, "",
+ retval = piix4_add_adapter(dev, retval, false, 0, false, "",
&piix4_main_adapters[0]);
if (retval < 0)
return retval;
@@ -827,7 +902,7 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
if (retval > 0) {
/* Try to add the aux adapter if it exists,
* piix4_add_adapter will clean up if this fails */
- piix4_add_adapter(dev, retval, false, 0,
+ piix4_add_adapter(dev, retval, false, 0, false,
is_sb800 ? piix4_aux_port_name_sb800 : "",
&piix4_aux_adapter);
}
--
2.14.1
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