>From 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) <arn...@mind.be>
---
This patch is based on v3.17-rc1.
Build-tested with omap2plus_defconfig.
Runtime tested based on v3.4.97 with a custom config.
v2: use dummy transfer instead of retrying (Laxman Dewangan)
---
drivers/mfd/tps65910.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/mfd/tps65910.c b/drivers/mfd/tps65910.c
index f243e75..7612d89 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);
--
2.1.0
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