From: Uwe Kleine-König u.kleine-koenig@pengutronix.de
stable inclusion from stable-v5.10.150 commit ea4dcd3d6accf2bbe87314cad428c40ed2b31dae category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6D0XA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 7f4f1096d5921f5d90547596f9ce80e0b924f887 upstream.
After the result of the previous conversion is read the chip automatically starts a new conversion and doesn't accept new i2c transfers until this conversion is completed which makes the function return failure.
So add an early return iff the programming of the new address isn't needed. Note this will not fix the problem in general, but all cases that are currently used. Once this changes we get the failure back, but this can be addressed when the need arises.
Fixes: 69548b7c2c4f ("iio: adc: ltc2497: split protocol independent part in a separate module ") Reported-by: Meng Li Meng.Li@windriver.com Signed-off-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Tested-by: Denys Zagorui dzagorui@cisco.com Cc: Stable@vger.kernel.org Link: https://lore.kernel.org/r/20220815091647.1523532-1-dzagorui@cisco.com Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- drivers/iio/adc/ltc2497.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c index 1adddf5a88a9..61f373fab9a1 100644 --- a/drivers/iio/adc/ltc2497.c +++ b/drivers/iio/adc/ltc2497.c @@ -41,6 +41,19 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata, }
*val = (be32_to_cpu(st->buf) >> 14) - (1 << 17); + + /* + * The part started a new conversion at the end of the above i2c + * transfer, so if the address didn't change since the last call + * everything is fine and we can return early. + * If not (which should only happen when some sort of bulk + * conversion is implemented) we have to program the new + * address. Note that this probably fails as the conversion that + * was triggered above is like not complete yet and the two + * operations have to be done in a single transfer. + */ + if (ddata->addr_prev == address) + return 0; }
ret = i2c_smbus_write_byte(st->client,