From: Stephen Warren swarren@wwwdotorg.org To: u-boot@lists.denx.de, Heiko Schocher hs@denx.de, Cc: Stephen Warren swarren@nvidia.com, Tom Warren twarren@nvidia.com Date: 2014/06/25 19:05 Subject: [U-Boot] [PATCH 1/3] i2c: tegra: use repeated start for reads Sent by: u-boot-bounces@lists.denx.de
From: Stephen Warren swarren@nvidia.com
I2C read transactions are typically implemented as follows:
START(write) address REPEATED_START(read) data... STOP
However, Tegra's I2C driver currently implements reads as follows:
START(write) address STOP START(read) data... STOP
This sequence confuses at least the AS3722 PMIC on the Jetson TK1 board, leading to corrupted read data in some cases. Fix the driver to chain the transactions together using repeated starts to solve this.
While I agree to use Repeated START I just wanted to share this: A common reason for STOP START(read) sequence not working sometimes is that the driver initializes STOP but does not wait for the STOP to complete before issuing a START.
Jocke