Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965631AbbLOXPU (ORCPT ); Tue, 15 Dec 2015 18:15:20 -0500 Received: from unicorn.mansr.com ([81.2.72.234]:41842 "EHLO unicorn.mansr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754331AbbLOXPR (ORCPT ); Tue, 15 Dec 2015 18:15:17 -0500 From: Mans Rullgard To: Wolfram Sang , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/2] i2c: xlr: fix extra read/write at end of rx transfer Date: Tue, 15 Dec 2015 23:15:05 +0000 Message-Id: <1450221306-5289-1-git-send-email-mans@mansr.com> X-Mailer: git-send-email 2.6.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4280 Lines: 130 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 --- Changes: - refuse zero-length transfers and stop advertising I2C_FUNC_SMBUS_QUICK --- drivers/i2c/busses/i2c-xlr.c | 50 ++++++++++++++++++++++++-------------------- 1 file changed, 27 insertions(+), 23 deletions(-) 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 @@ 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 = { -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/