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Re: [PATCH v3 1/4] i2c: tegra: implement slave mode


On 24.07.2015 12:27, Wolfram Sang wrote:
Still doesn't work for me and I think I understand why. Do you run your
I2C controller in slave mode only?


That might work, but using it in
master/slave mode simultanously won't work yet as I see it:

* After every transfer (as master), clocks get disabled. I assume the IP
   core won't be able to detect its own address then.

At the begin of my work on this patchset I even denied clock disable call if slave is registered (to minimize code that can affect transfer). If only slave mode is used, then this logic is not needed.

* There is this code in tegra_i2c_init():

	if (!i2c_dev->is_dvc) {
		u32 sl_cfg = i2c_readl(i2c_dev, I2C_SL_CNFG);
		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);


   It probably messes up the slave initialization in tegra_reg_slave().
   At least I see that the slave address gets overwritten when I peek
   the register after boot.

tegra_i2c_init is called on probe and resume. Also it is called in case of xfer fail. If xfer is ok, then I think slave addr must be kept unchanged.

Does that make sense to you?

As far as I understand it is a loopback mode. Probably it will not work (Stephen Warren already mentioned this).
But we can try to run it.