| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.17 47/67] i2c: recovery: if possible send STOP with recovery pulses | Date | Mon, 16 Jul 2018 09:35:16 +0200 |
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4.17-stable review patch. If anyone has any objections, please let me know.
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From: Wolfram Sang <wsa+renesas@sang-engineering.com>
commit abe41184abac487264a4904bfcff2d5500dccce6 upstream.
I2C clients may misunderstand recovery pulses if they can't read SDA to bail out early. In the worst case, as a write operation. To avoid that and if we can write SDA, try to send STOP to avoid the misinterpretation.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Reviewed-by: Peter Rosin <peda@axentia.se> Signed-off-by: Wolfram Sang <wsa@the-dreams.de> Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/i2c/i2c-core-base.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
--- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -198,7 +198,16 @@ int i2c_generic_scl_recovery(struct i2c_ val = !val; bri->set_scl(adap, val); - ndelay(RECOVERY_NDELAY); + + /* + * If we can set SDA, we will always create STOP here to ensure + * the additional pulses will do no harm. This is achieved by + * letting SDA follow SCL half a cycle later. + */ + ndelay(RECOVERY_NDELAY / 2); + if (bri->set_sda) + bri->set_sda(adap, val); + ndelay(RECOVERY_NDELAY / 2); } /* check if recovery actually succeeded */
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