On 06/25/2014 08:12 PM, Simon Glass wrote:
Hi Stephen,
On 25 June 2014 10:57, Stephen Warren swarren@wwwdotorg.org wrote:
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.
diff --git a/drivers/i2c/tegra_i2c.c b/drivers/i2c/tegra_i2c.c
@@ -209,7 +212,8 @@ static int send_recv_packets(struct i2c_bus *i2c_bus, int_status = readl(&control->int_status); writel(int_status, &control->int_status);
send_packet_headers(i2c_bus, trans, 1);
send_packet_headers(i2c_bus, trans, 1,trans->flags & I2C_USE_REPEATED_START);I'm not sure if it is safe/advisable to pass this value to a bool type. Perhaps the function parameter should be int? My understanding of bool is that it is supposed to be 0 or 1, but I'm happy to be corrected.
I believe that the "promotion" from int to bool clamps the range to 0 or 1. I've certainly seen compilers warn that this promotion might be a performance issue!. If not, I can always add !! in front.