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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 raise logger level for TX abort messages when the segment length
is zero. Adjust dw_i2c_transfer() to allow zero-segment-length
messages to be passed thru to _dw_i2c_transfer().

Tested as part of entire i2c-detect patch train.

Change-Id: I518e849f4c476c264a1464886b1853af66c0b29d
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63561
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@tutanota.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
This commit is contained in:
Matt DeVillier 2022-04-11 17:10:09 -05:00 committed by Paul Fagerburg
parent 1017a8fc5f
commit 57097130d5
1 changed files with 8 additions and 3 deletions
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11
src/drivers/i2c/designware/dw_i2c.c
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@ -358,6 +358,7 @@ static enum cb_err _dw_i2c_transfer(unsigned int bus, const struct i2c_msg *segm
struct dw_i2c_regs *regs;
size_t byte;
enum cb_err ret = CB_ERR;
bool seg_zero_len = segments->len == 0;
regs = (struct dw_i2c_regs *)dw_i2c_base_address(bus);
if (!regs) {
@ -374,6 +375,10 @@ static enum cb_err _dw_i2c_transfer(unsigned int bus, const struct i2c_msg *segm
dw_i2c_enable(regs);
if (seg_zero_len)
/* stop immediately */
write32(&regs->cmd_data, CMD_DATA_STOP);
/* Process each segment */
while (count--) {
if (CONFIG(DRIVERS_I2C_DESIGNWARE_DEBUG)) {
@ -424,8 +429,8 @@ static enum cb_err _dw_i2c_transfer(unsigned int bus, const struct i2c_msg *segm
/* 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));
printk(seg_zero_len ? BIOS_SPEW : 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;
@ -462,7 +467,7 @@ static enum cb_err dw_i2c_transfer(unsigned int bus, const struct i2c_msg *msg,
size_t start;
uint16_t addr;
if (count == 0 || !msg)
if (!msg)
return -1;
/* Break up the transfers at the differing slave address boundary. */