"HU TAO-TGHK48" <taohu@xxxxxxxxxxxx> writes:
> I think we also need extra patch for fixing stability issue.
>
> Sometimes after back from retention/off mode, OMAP3430 I2C controller
> stops working even all register settings are restored.
>
> OMAP3430 TRM says: "During active mode (I2Ci.I2C_CON[15] I2C_EN bit is
> set to 1), make no changes to the I2Ci.I2C_SCLL and I2Ci.I2C_SCLH
> registers.
> Changes may result in unpredictable behavior."
>
> diff --git a/drivers/i2c/busses/i2c-omap.c
> b/drivers/i2c/busses/i2c-omap.c index 5ce055c..b084209 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -238,12 +238,14 @@ static void omap_i2c_unidle(struct omap_i2c_dev
> *dev)
> clk_enable(dev->iclk);
> clk_enable(dev->fclk);
> if (cpu_is_omap34xx()) {
> + omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, 0);
> omap_i2c_write_reg(dev, OMAP_I2C_PSC_REG,
> dev->pscstate);
> omap_i2c_write_reg(dev, OMAP_I2C_SCLL_REG,
> dev->scllstate);
> omap_i2c_write_reg(dev, OMAP_I2C_SCLH_REG,
> dev->sclhstate);
> omap_i2c_write_reg(dev, OMAP_I2C_BUF_REG,
> dev->bufstate);
> omap_i2c_write_reg(dev, OMAP_I2C_SYSC_REG,
> dev->syscstate);
> omap_i2c_write_reg(dev, OMAP_I2C_WE_REG, dev->westate);
> + omap_i2c_write_reg(dev, OMAP_I2C_CON_REG,
> OMAP_I2C_CON_EN);
> }
> dev->idle = 0;
> omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, dev->iestate);
Shouldn't you do a read-modify-write of I2C_CON_REG here? Otherwise,
you're loosing any of the other settings in I2C_CON_REG.
Not being an expert in the I2C hardware, I'm not sure if it matters,
but this doesn't seem quite right due to possible side effects.
Kevin
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