From: Stephen Warren Date: Mon, 6 Jun 2011 17:25:19 +0000 (-0600) Subject: i2c: tegra: Assign unused slave address X-Git-Tag: v3.0-rc7~33^2^3 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5afa9d35782890e8fbd972f12ee5183ba5feb81d;p=pandora-kernel.git 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 http://www.spinics.net/lists/linux-i2c/msg05437.html In turned based on internal changes by: Bharat Nihalani 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 Signed-off-by: Ben Dooks --- Reading git-diff-tree failed