Change in coreboot[master]: drivers/i2c/dw_i2c: Adjust to handle 0-byte transfers

[Matt DeVillier (Code Review)]

Matt DeVillier has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/63561 )

Change subject: drivers/i2c/dw_i2c: Adjust to handle 0-byte transfers
......................................................................

drivers/i2c/dw_i2c: Adjust to handle 0-byte transfers

0-byte writes can be used as a way to probe/check presence of an i2c
device, so adjust _dw_i2c_transfer() to immediately set the STOP bit
and suppress TX abort messages when the segment length is zero.

Tested as part of entire i2c-detect patch train.

Change-Id: I518e849f4c476c264a1464886b1853af66c0b29d
Signed-off-by: Matt DeVillier 
---
M src/drivers/i2c/designware/dw_i2c.c
1 file changed, 7 insertions(+), 2 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/61/63561/1

diff --git a/src/drivers/i2c/designware/dw_i2c.c b/src/drivers/i2c/designware/dw_i2c.c
index 56f3f27..1a61282 100644
--- a/src/drivers/i2c/designware/dw_i2c.c
+++ b/src/drivers/i2c/designware/dw_i2c.c
@@ -374,6 +374,10 @@

dw_i2c_enable(regs);

+	if (segments->len == 0)
+		/* stop immediately */
+		write32(&regs->cmd_data, CMD_DATA_STOP);
+
    /* Process each segment */
    while (count--) {
    	if (CONFIG(DRIVERS_I2C_DESIGNWARE_DEBUG)) {
@@ -424,8 +428,9 @@

/* Check TX abort */
    if (read32(&regs->raw_intr_stat) & INTR_STAT_TX_ABORT) {
-		printk(BIOS_ERR, "I2C TX abort detected (%08x)\n",
-		       read32(&regs->tx_abort_source));
+		if (segments->len != 0)
+			printk(BIOS_ERR, "I2C TX abort detected (%08x)\n",
+			      read32(&regs->tx_abort_source));
    	/* clear INTR_STAT_TX_ABORT */
    	read32(&regs->clear_tx_abrt_intr);
    	goto out;