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| author | Vincent Jardin <vjardin@free.fr> | 2026-07-13 20:11:59 +0200 |
|---|---|---|
| committer | Andi Shyti <andi.shyti@kernel.org> | 2026-07-14 16:39:39 +0200 |
| commit | cb2fc37857693b55909fb77dc2c87cfbc1cdc476 (patch) | |
| tree | cd412c91ed352e7d5e4565a356482cda7fc5a0d3 /drivers | |
| parent | 627b6c94b817c2ee00c854d102a5da08105ad0a7 (diff) | |
| download | linux-next-cb2fc37857693b55909fb77dc2c87cfbc1cdc476.tar.gz linux-next-cb2fc37857693b55909fb77dc2c87cfbc1cdc476.zip | |
i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)
SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the atomic
(polling) path 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 for
this i2c controller.
Reading I2DR to obtain the count likewise arms the next byte on the
count > I2C_SMBUS_BLOCK_MAX path, which also returned -EPROTO directly
and left the bus held.
Handle both: NACK the in-flight dummy byte (TXAK) and extend msgs->len so
the existing last-byte handling emits STOP; the dummy byte is discarded.
A count of 0 is a valid empty block read; a count above
I2C_SMBUS_BLOCK_MAX is still reported as -EPROTO, but only after the bus
has been released.
The interrupt-driven path has the same flaw from a later commit and is
fixed separately, as it carries a different Fixes: tag and stable range.
Fixes: 8e8782c71595 ("i2c: imx: add SMBus block read support")
Signed-off-by: Vincent Jardin <vjardin@free.fr>
Cc: <stable@vger.kernel.org> # v3.16+
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-v3-1-073ac9e103a5@free.fr
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/i2c/busses/i2c-imx.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c index 28313d0fad37..cfd1e63359e7 100644 --- a/drivers/i2c/busses/i2c-imx.c +++ b/drivers/i2c/busses/i2c-imx.c @@ -1415,6 +1415,7 @@ static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx, int i, result; unsigned int temp; int block_data = msgs->flags & I2C_M_RECV_LEN; + int block_err = 0; result = i2c_imx_prepare_read(i2c_imx, msgs, false); if (result) @@ -1436,8 +1437,20 @@ static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx, */ if ((!i) && block_data) { len = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); - if ((len == 0) || (len > I2C_SMBUS_BLOCK_MAX)) - return -EPROTO; + 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. + */ + if (len > I2C_SMBUS_BLOCK_MAX) + block_err = -EPROTO; + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); + temp |= I2CR_TXAK; + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); + msgs->buf[0] = 0; + msgs->len = 2; + continue; + } dev_dbg(&i2c_imx->adapter.dev, "<%s> read length: 0x%X\n", __func__, len); @@ -1485,7 +1498,7 @@ static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx, "<%s> read byte: B%d=0x%X\n", __func__, i, msgs->buf[i]); } - return 0; + return block_err; } static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs, |