From: Vincent Jardin Date: Mon, 13 Jul 2026 18:12:00 +0000 (+0200) Subject: i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ) X-Git-Tag: v7.2-rc4~10^2~3 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=07fd9385f0d87dff4b34f355f68adf701080cb24;p=thirdparty%2Flinux.git i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ) 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: 5f5c2d4579ca ("i2c: imx: prevent rescheduling in non dma mode") Signed-off-by: Vincent Jardin Cc: # v6.13+ Acked-by: Oleksij Rempel Acked-by: Carlos Song Reviewed-by: Stefan Eichenberger Signed-off-by: Andi Shyti Link: https://lore.kernel.org/r/20260713-for-upstream-i2c-lx2160-fix-v1-v3-2-073ac9e103a5@free.fr --- diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c index cfd1e63359e7..d5e6e2eca3b3 100644 --- a/drivers/i2c/busses/i2c-imx.c +++ b/drivers/i2c/busses/i2c-imx.c @@ -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;