From be1c770028b832945680ebf5c0d49b831ba719d5 Mon Sep 17 00:00:00 2001 From: "Arnout Vandecappelle (Essensium/Mind)" Date: Fri, 22 Aug 2014 17:30:56 +0200 Subject: mfd: tps65910: Work around silicon erratum SWCZ010 http://www.ti.com/lit/pdf/SWCZ010: Glitch on SDA-SCL not managed correctly by the I2C IP Impact: The standard specifies that the I2C transfer should restart on a start event in all cases. The current design does not support two consecutive Start conditions. This can cause the first real access after such a glitch to be corrupted. Description: An unexpected glitch on SDA and SCL can generate a wrong start event. In the current design, the SCL line must toggle two times to detect a new start event and completely restart the I2C access; hence the real start event is not detected in the case of a single SCL toggle. Workaround: Repeat I2C access. A simpler workaround is to make a dummy transfer just before the first access to the tps65910 chip. This can be done unconditionally. Signed-off-by: Arnout Vandecappelle (Essensium/Mind) Acked-by: Mark Brown Signed-off-by: Lee Jones --- drivers/mfd/tps65910.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'drivers/mfd') diff --git a/drivers/mfd/tps65910.c b/drivers/mfd/tps65910.c index f243e75d28f3..7612d89850dd 100644 --- a/drivers/mfd/tps65910.c +++ b/drivers/mfd/tps65910.c @@ -486,6 +486,11 @@ static int tps65910_i2c_probe(struct i2c_client *i2c, tps65910->i2c_client = i2c; tps65910->id = chip_id; + /* Work around silicon erratum SWCZ010: the tps65910 may miss the + * first I2C transfer. So issue a dummy transfer before the first + * real transfer. + */ + i2c_master_send(i2c, "", 1); tps65910->regmap = devm_regmap_init_i2c(i2c, &tps65910_regmap_config); if (IS_ERR(tps65910->regmap)) { ret = PTR_ERR(tps65910->regmap); -- cgit v1.2.3