Commit a45af72a authored by Måns Rullgård's avatar Måns Rullgård Committed by Wolfram Sang
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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: default avatarMans Rullgard <mans@mansr.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 75d31c23

drivers/i2c/busses/i2c-xlr.c

+27 −23
Original line number Diff line number Diff line
@@ -89,38 +89,43 @@ static int xlr_i2c_tx(struct xlr_i2c_private *priv, u16 len, 
	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 @@ static int xlr_i2c_rx(struct xlr_i2c_private *priv, u16 len, u8 *buf, u16 addr) 
	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 @@ retry: 
		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 int xlr_i2c_xfer(struct i2c_adapter *adap, 
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 = {

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