i2c: xlr: fix extra read/write at end of rx transfer
The BYTECNT register holds the transfer size minus one. Setting it to
the correct value removes the need for a dummy read/write at the end of
each transfer. As zero-length transfers are not supported, do not
advertise I2C_FUNC_SMBUS_QUICK.
In other words, this patch makes the driver transfer the number of bytes
requested unless this is zero, which is not supported by the hardware
and is thus refused.
Signed-off-by: Mans Rullgard <mans@mansr.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
diff --git a/drivers/i2c/busses/i2c-xlr.c b/drivers/i2c/busses/i2c-xlr.c
index 10fb916..2cfaba7 100644
--- a/drivers/i2c/busses/i2c-xlr.c
+++ b/drivers/i2c/busses/i2c-xlr.c
@@ -89,38 +89,43 @@
unsigned long timeout, stoptime, checktime;
u32 i2c_status;
int pos, timedout;
- u8 offset, byte;
+ u8 offset;
+ u32 xfer;
+
+ if (!len)
+ return -EOPNOTSUPP;
offset = buf[0];
xlr_i2c_wreg(priv->iobase, XLR_I2C_ADDR, offset);
xlr_i2c_wreg(priv->iobase, XLR_I2C_DEVADDR, addr);
xlr_i2c_wreg(priv->iobase, XLR_I2C_CFG,
XLR_I2C_CFG_ADDR | priv->cfg->cfg_extra);
- xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len - 1);
timeout = msecs_to_jiffies(XLR_I2C_TIMEOUT);
stoptime = jiffies + timeout;
timedout = 0;
- pos = 1;
-retry:
+
if (len == 1) {
- xlr_i2c_wreg(priv->iobase, XLR_I2C_STARTXFR,
- XLR_I2C_STARTXFR_ND);
+ xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len - 1);
+ xfer = XLR_I2C_STARTXFR_ND;
+ pos = 1;
} else {
- xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT, buf[pos]);
- xlr_i2c_wreg(priv->iobase, XLR_I2C_STARTXFR,
- XLR_I2C_STARTXFR_WR);
+ xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len - 2);
+ xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT, buf[1]);
+ xfer = XLR_I2C_STARTXFR_WR;
+ pos = 2;
}
+retry:
+ /* retry can only happen on the first byte */
+ xlr_i2c_wreg(priv->iobase, XLR_I2C_STARTXFR, xfer);
+
while (!timedout) {
checktime = jiffies;
i2c_status = xlr_i2c_rdreg(priv->iobase, XLR_I2C_STATUS);
- if (i2c_status & XLR_I2C_SDOEMPTY) {
- pos++;
- /* need to do a empty dataout after the last byte */
- byte = (pos < len) ? buf[pos] : 0;
- xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT, byte);
+ if ((i2c_status & XLR_I2C_SDOEMPTY) && pos < len) {
+ xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT, buf[pos++]);
/* reset timeout on successful xmit */
stoptime = jiffies + timeout;
@@ -149,11 +154,13 @@
u32 i2c_status;
unsigned long timeout, stoptime, checktime;
int nbytes, timedout;
- u8 byte;
+
+ if (!len)
+ return -EOPNOTSUPP;
xlr_i2c_wreg(priv->iobase, XLR_I2C_CFG,
XLR_I2C_CFG_NOADDR | priv->cfg->cfg_extra);
- xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len);
+ xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len - 1);
xlr_i2c_wreg(priv->iobase, XLR_I2C_DEVADDR, addr);
timeout = msecs_to_jiffies(XLR_I2C_TIMEOUT);
@@ -167,14 +174,11 @@
checktime = jiffies;
i2c_status = xlr_i2c_rdreg(priv->iobase, XLR_I2C_STATUS);
if (i2c_status & XLR_I2C_RXRDY) {
- if (nbytes > len)
+ if (nbytes >= len)
return -EIO; /* should not happen */
- /* we need to do a dummy datain when nbytes == len */
- byte = xlr_i2c_rdreg(priv->iobase, XLR_I2C_DATAIN);
- if (nbytes < len)
- buf[nbytes] = byte;
- nbytes++;
+ buf[nbytes++] =
+ xlr_i2c_rdreg(priv->iobase, XLR_I2C_DATAIN);
/* reset timeout on successful read */
stoptime = jiffies + timeout;
@@ -228,7 +232,7 @@
static u32 xlr_func(struct i2c_adapter *adap)
{
/* Emulate SMBUS over I2C */
- return I2C_FUNC_SMBUS_EMUL | I2C_FUNC_I2C;
+ return (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK) | I2C_FUNC_I2C;
}
static struct i2c_algorithm xlr_i2c_algo = {