Skip to content

Commit

Permalink
i2c-i801: Consolidate polling
Browse files Browse the repository at this point in the history 
(Based on earlier work by Daniel Kurtz.)

Come up with a consistent, driver-wide strategy for event polling. For
intermediate steps of byte-by-byte block transactions, check for
BYTE_DONE or any error flag being set. At the end of every transaction
(regardless of PEC being used), check for both BUSY being cleared and
INTR or any error flag being set. This ensures proper action for all
transaction types.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Daniel Kurtz <djkurtz@chromium.org>
  • Loading branch information
Jean Delvare authored and Jean Delvare committed Jul 24, 2012
1 parent 37af871 commit 6cad93c
Showing 1 changed file with 53 additions and 55 deletions.
108 changes: 53 additions & 55 deletions drivers/i2c/busses/i2c-i801.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -206,13 +206,17 @@ static int i801_check_pre(struct i801_priv *priv)
return 0;
}

/* Convert the status register to an error code, and clear it. */
static int i801_check_post(struct i801_priv *priv, int status, int timeout)
/*
* Convert the status register to an error code, and clear it.
* Note that status only contains the bits we want to clear, not the
* actual register value.
*/
static int i801_check_post(struct i801_priv *priv, int status)
{
int result = 0;

/* If the SMBus is still busy, we give up */
if (timeout) {
if (unlikely(status < 0)) {
dev_err(&priv->pci_dev->dev, "Transaction timeout\n");
/* try to stop the current command */
dev_dbg(&priv->pci_dev->dev, "Terminating the current operation\n");
Expand Down Expand Up @@ -245,64 +249,68 @@ static int i801_check_post(struct i801_priv *priv, int status, int timeout)
dev_dbg(&priv->pci_dev->dev, "Lost arbitration\n");
}

if (result) {
/* Clear error flags */
outb_p(status & STATUS_FLAGS, SMBHSTSTS(priv));
status = inb_p(SMBHSTSTS(priv)) & STATUS_FLAGS;
if (status) {
dev_warn(&priv->pci_dev->dev, "Failed clearing status "
"flags at end of transaction (%02x)\n",
status);
}
}
/* Clear status flags except BYTE_DONE, to be cleared by caller */
outb_p(status, SMBHSTSTS(priv));

return result;
}

static int i801_transaction(struct i801_priv *priv, int xact)
/* Wait for BUSY being cleared and either INTR or an error flag being set */
static int i801_wait_intr(struct i801_priv *priv)
{
int status;
int result;
int timeout = 0;

result = i801_check_pre(priv);
if (result < 0)
return result;

/* the current contents of SMBHSTCNT can be overwritten, since PEC,
* SMBSCMD are passed in xact */
outb_p(xact | SMBHSTCNT_START, SMBHSTCNT(priv));
int status;

/* We will always wait for a fraction of a second! */
do {
usleep_range(250, 500);
status = inb_p(SMBHSTSTS(priv));
} while ((status & SMBHSTSTS_HOST_BUSY) && (timeout++ < MAX_RETRIES));
} while (((status & SMBHSTSTS_HOST_BUSY) ||
!(status & (STATUS_ERROR_FLAGS | SMBHSTSTS_INTR))) &&
(timeout++ < MAX_RETRIES));

result = i801_check_post(priv, status, timeout > MAX_RETRIES);
if (result < 0)
return result;

outb_p(SMBHSTSTS_INTR, SMBHSTSTS(priv));
return 0;
if (timeout > MAX_RETRIES) {
dev_dbg(&priv->pci_dev->dev, "INTR Timeout!\n");
return -ETIMEDOUT;
}
return status & (STATUS_ERROR_FLAGS | SMBHSTSTS_INTR);
}

/* wait for INTR bit as advised by Intel */
static void i801_wait_hwpec(struct i801_priv *priv)
/* Wait for either BYTE_DONE or an error flag being set */
static int i801_wait_byte_done(struct i801_priv *priv)
{
int timeout = 0;
int status;

/* We will always wait for a fraction of a second! */
do {
usleep_range(250, 500);
status = inb_p(SMBHSTSTS(priv));
} while ((!(status & SMBHSTSTS_INTR))
&& (timeout++ < MAX_RETRIES));
} while (!(status & (STATUS_ERROR_FLAGS | SMBHSTSTS_BYTE_DONE)) &&
(timeout++ < MAX_RETRIES));

if (timeout > MAX_RETRIES) {
dev_dbg(&priv->pci_dev->dev, "BYTE_DONE Timeout!\n");
return -ETIMEDOUT;
}
return status & STATUS_ERROR_FLAGS;
}

static int i801_transaction(struct i801_priv *priv, int xact)
{
int status;
int result;

if (timeout > MAX_RETRIES)
dev_dbg(&priv->pci_dev->dev, "PEC Timeout!\n");
result = i801_check_pre(priv);
if (result < 0)
return result;

outb_p(status & STATUS_FLAGS, SMBHSTSTS(priv));
/* the current contents of SMBHSTCNT can be overwritten, since PEC,
* SMBSCMD are passed in xact */
outb_p(xact | SMBHSTCNT_START, SMBHSTCNT(priv));

status = i801_wait_intr(priv);
return i801_check_post(priv, status);
}

static int i801_block_transaction_by_block(struct i801_priv *priv,
Expand Down Expand Up @@ -353,7 +361,6 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
int smbcmd;
int status;
int result;
int timeout;

result = i801_check_pre(priv);
if (result < 0)
Expand Down Expand Up @@ -381,17 +388,9 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
outb_p(inb(SMBHSTCNT(priv)) | SMBHSTCNT_START,
SMBHSTCNT(priv));

/* We will always wait for a fraction of a second! */
timeout = 0;
do {
usleep_range(250, 500);
status = inb_p(SMBHSTSTS(priv));
} while (!(status & (SMBHSTSTS_BYTE_DONE | STATUS_ERROR_FLAGS))
&& (timeout++ < MAX_RETRIES));

result = i801_check_post(priv, status, timeout > MAX_RETRIES);
if (result < 0)
return result;
status = i801_wait_byte_done(priv);
if (status)
goto exit;

if (i == 1 && read_write == I2C_SMBUS_READ
&& command != I2C_SMBUS_I2C_BLOCK_DATA) {
Expand All @@ -418,10 +417,12 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
outb_p(data->block[i+1], SMBBLKDAT(priv));

/* signals SMBBLKDAT ready */
outb_p(SMBHSTSTS_BYTE_DONE | SMBHSTSTS_INTR, SMBHSTSTS(priv));
outb_p(SMBHSTSTS_BYTE_DONE, SMBHSTSTS(priv));
}

return 0;
status = i801_wait_intr(priv);
exit:
return i801_check_post(priv, status);
}

static int i801_set_block_buffer_mode(struct i801_priv *priv)
Expand Down Expand Up @@ -476,9 +477,6 @@ static int i801_block_transaction(struct i801_priv *priv,
read_write,
command, hwpec);

if (result == 0 && hwpec)
i801_wait_hwpec(priv);

if (command == I2C_SMBUS_I2C_BLOCK_DATA
&& read_write == I2C_SMBUS_WRITE) {
/* restore saved configuration register value */
Expand Down

0 comments on commit 6cad93c

Please sign in to comment.