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i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ)

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SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the
interrupt-driven block-read state machine rejects it as -EPROTO. Worse,
it returns without a NACK+STOP: the next receive cycle has already
started, so the target keeps holding SDA and the bus stays stuck until a
power cycle of this i2c controller.

Accept count=0: NACK the in-flight dummy byte (TXAK) and set msg->len to
2 so i2c_imx_isr_read_continue() emits STOP via its normal last-byte
path. The dummy byte is discarded; block-read callers only consume
buf[0..count-1].

Reading I2DR has likewise already armed the next byte on the
count > I2C_SMBUS_BLOCK_MAX error path, so NACK it (TXAK) before aborting
with -EPROTO; otherwise the failing transfer's STOP cannot complete and
the bus stays held.

The atomic path regressed earlier (v3.16) and is fixed separately; this
patch covers only the v6.13 state-machine rework.

Fixes: 5f5c2d4579 ("i2c: imx: prevent rescheduling in non dma mode")
Signed-off-by: Vincent Jardin <vjardin@free.fr>
Cc: <stable@vger.kernel.org> # v6.13+
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Carlos Song <carlos.song@nxp.com>
Reviewed-by: Stefan Eichenberger <eichest@gmail.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260713-for-upstream-i2c-lx2160-fix-v1-v3-2-073ac9e103a5@free.fr
This commit is contained in:
Vincent Jardin
2026-07-13 20:12:00 +02:00
committed by Andi Shyti
parent cb2fc37857
commit 07fd9385f0
1 changed files with 17 additions and 0 deletions
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17
drivers/i2c/busses/i2c-imx.c
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@@ -1061,11 +1061,28 @@ static inline enum imx_i2c_state i2c_imx_isr_read_continue(struct imx_i2c_struct
static inline void i2c_imx_isr_read_block_data_len(struct imx_i2c_struct *i2c_imx)
{
u8 len = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
unsigned int temp;
if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) {
/*
* SMBus 3.1 6.5.7: support count byte of 0.
* I2C_SMBUS_BLOCK_MAX case should not hold the SDA either.
* So NACK it (TXAK) to not hold the bus.
*/
temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
temp |= I2CR_TXAK;
imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
if (len == 0) {
i2c_imx->msg->buf[i2c_imx->msg_buf_idx++] = 0;
i2c_imx->msg->len = 2;
return;
}
i2c_imx->isr_result = -EPROTO;
i2c_imx->state = IMX_I2C_STATE_FAILED;
wake_up(&i2c_imx->queue);
return;
}
i2c_imx->msg->len += len;
i2c_imx->msg->buf[i2c_imx->msg_buf_idx++] = len;