From b76911d2fe1462e1fc7c449e3e6aef76331e816e Mon Sep 17 00:00:00 2001 From: Alexander Kochetkov Date: Sat, 22 Nov 2014 23:47:13 +0400 Subject: [PATCH] i2c: omap: don't reset controller if Arbitration Lost detected Arbitration Lost is an expected situation in a multimaster environment. I2C controller (IP) correctly detect and report AL. The only one visible reason for resetting IP in the AL case is to avoid advisory 1.94 (omap3) and errata i595 (omap4): "I2C: After an Arbitration is Lost the Module Incorrectly Starts the Next Transfer". Errata workaround states: "The MST and STT bits inside I2C_CON should be set to 1 at the same moment (avoid setting the MST bit to 1 while STT = 0)." The driver never set MST and STT bits separately and doesn't create condition for errata. So the reset is not necessary. Also corrected return value for AL to -EAGAIN. Tested on Beagleboard XM C. Tested on BBB and AM437x Starter Kit by Felipe Balbi. Signed-off-by: Alexander Kochetkov Tested-by: Felipe Balbi Reviewed-by: Felipe Balbi Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-omap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index 4426e9970e8f..b70270d8efdc 100644 --- a/drivers/i2c/busses/i2c-omap.c +++ b/drivers/i2c/busses/i2c-omap.c @@ -703,13 +703,15 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap, return 0; /* We have an error */ - if (dev->cmd_err & (OMAP_I2C_STAT_AL | OMAP_I2C_STAT_ROVR | - OMAP_I2C_STAT_XUDF)) { + if (dev->cmd_err & (OMAP_I2C_STAT_ROVR | OMAP_I2C_STAT_XUDF)) { omap_i2c_reset(dev); __omap_i2c_init(dev); return -EIO; } + if (dev->cmd_err & OMAP_I2C_STAT_AL) + return -EAGAIN; + if (dev->cmd_err & OMAP_I2C_STAT_NACK) { if (msg->flags & I2C_M_IGNORE_NAK) return 0; -- GitLab