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authorStephen Warren <swarren@nvidia.com>2011-06-06 11:25:19 -0600
committerBen Dooks <ben-linux@fluff.org>2011-06-27 23:03:42 +0100
commit5afa9d35782890e8fbd972f12ee5183ba5feb81d (patch)
treeb34ed30d274eaef7666b98f159d59e80b4c8a8f5 /drivers/i2c
parentaf4087e0e682df12bdffec5cfafc2fec9208716e (diff)
i2c: tegra: Assign unused slave address
On Tegra, we should always use the "new" I2C slave controller, to avoid issues with the old controller. This was implemented in commit 65a1a0a "i2c: tegra: Enable new slave mode." There is currently no driver for the Tegra I2C slave controller upstream. Additionally, the controller cannot be completely disabled. Instead, we need to: a) Set I2C_SL_CNFG_NACK to make the controller automatically NACK any incoming transactions. b) The controller's definition of NACK isn't identical to the I2C protocol's definition. Specifically, it will perform a standard NACK, but *also* continue to hold the clock line low in expectation of receiving more data. This can hang the bus, or at least cause transaction timeouts, if something starts a transaction that matches the controller's slave address. Since the default address is 0x00, the general call address, this does occur in practice. To avoid this, we explicitly program a slave address that is reserved for future expansion. For current boards, this guarantees the address will never be used. If a future board ever needs to use this address, we can add platform data to determine a board-specific safe address. 0xfc is picked by this patch. This patch is based on a change previously posted by: Wei Ni <wni@nvidia.com> http://www.spinics.net/lists/linux-i2c/msg05437.html In turned based on internal changes by: Bharat Nihalani <bnihalani@nvidia.com> A semantically equivalent change has been contained in the various ChromeOS kernels for a while. I tested this change on top of 3.0-rc2 on Harmony, and interacted with the WM8903 I2C-based audio codec. Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-tegra.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 4d9319665e3..fb3b4f8f815 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -40,8 +40,10 @@
#define I2C_CNFG_NEW_MASTER_FSM (1<<11)
#define I2C_STATUS 0x01C
#define I2C_SL_CNFG 0x020
+#define I2C_SL_CNFG_NACK (1<<1)
#define I2C_SL_CNFG_NEWSL (1<<2)
#define I2C_SL_ADDR1 0x02c
+#define I2C_SL_ADDR2 0x030
#define I2C_TX_FIFO 0x050
#define I2C_RX_FIFO 0x054
#define I2C_PACKET_TRANSFER_STATUS 0x058
@@ -337,7 +339,11 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
if (!i2c_dev->is_dvc) {
u32 sl_cfg = i2c_readl(i2c_dev, I2C_SL_CNFG);
- i2c_writel(i2c_dev, sl_cfg | I2C_SL_CNFG_NEWSL, I2C_SL_CNFG);
+ sl_cfg |= I2C_SL_CNFG_NACK | I2C_SL_CNFG_NEWSL;
+ i2c_writel(i2c_dev, sl_cfg, I2C_SL_CNFG);
+ i2c_writel(i2c_dev, 0xfc, I2C_SL_ADDR1);
+ i2c_writel(i2c_dev, 0x00, I2C_SL_ADDR2);
+
}
val = 7 << I2C_FIFO_CONTROL_TX_TRIG_SHIFT |