Hi Stephen,
On Fri, Feb 08, 2013 at 08:52:58PM -0700, Stephen Warren wrote:
> This implements a very basic I2C host driver for the BCM2835 SoC. Missing
> features so far are:
>
> * 10-bit addressing.
> * DMA.
>
> Reviewed-by: Grant Likely <[email protected]>
> Signed-off-by: Stephen Warren <[email protected]>
> ---
...
> +struct bcm2835_i2c_dev {
> + struct device *dev;
> + void __iomem *regs;
> + struct clk *clk;
> + struct i2c_adapter adapter;
> + struct completion completion;
> + u32 msg_err;
> + u8 *msg_buf;
> + size_t msg_buf_remaining;
> +};
> +
> +static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
> + u32 reg, u32 val)
> +{
> + writel(val, i2c_dev->regs + reg);
> +}
> +
> +static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
> +{
> + return readl(i2c_dev->regs + reg);
> +}
Hmm, not sure if those functions add readability, but no need to change.
> +
> +static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
> +{
> + u32 val;
> +
> + for (;;) {
> + if (!i2c_dev->msg_buf_remaining)
> + return;
> + val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
> + if (!(val & BCM2835_I2C_S_TXD))
> + break;
> + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
> + *i2c_dev->msg_buf);
> + i2c_dev->msg_buf++;
> + i2c_dev->msg_buf_remaining--;
> + }
while (i2c_dev->msg_buf_remaining) ...
?
> +}
> +
> +static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
> +{
> + u32 val;
> +
> + for (;;) {
> + if (!i2c_dev->msg_buf_remaining)
> + return;
> + val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
> + if (!(val & BCM2835_I2C_S_RXD))
> + break;
> + *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
> + BCM2835_I2C_FIFO);
> + i2c_dev->msg_buf++;
> + i2c_dev->msg_buf_remaining--;
> + }
ditto?
...
> + ret = wait_for_completion_timeout(&i2c_dev->completion,
> + BCM2835_I2C_TIMEOUT);
> + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
> + if (WARN_ON(ret == 0)) {
> + dev_err(i2c_dev->dev, "i2c transfer timed out\n");
> + return -ETIMEDOUT;
> + }
I'd suggest to skip the WARN_ON. Timeout is the expected case when you
want to read from an EEPROM which is just in the process of
erasing/writing data from the previous command.
...
> + adap = &i2c_dev->adapter;
> + i2c_set_adapdata(adap, i2c_dev);
> + adap->owner = THIS_MODULE;
> + adap->class = I2C_CLASS_HWMON;
Do you really need the class?
> + strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));
> + adap->algo = &bcm2835_i2c_algo;
> + adap->dev.parent = &pdev->dev;
> + adap->nr = -1;
If you are using '-1' anyhow, you could skip setting it and simply call
i2c_add_adapter(). Or you can init it here to pdev->id. Whatever you
prefer.
> +
> + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
> +
> + return i2c_add_numbered_adapter(adap);
> +}
> +
> +static int bcm2835_i2c_remove(struct platform_device *pdev)
> +{
> + struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
> +
> + i2c_del_adapter(&i2c_dev->adapter);
Is it guaranteed that interrupts cannot occur anymore? Otherwise OOPS
might happen, since the adapter is cleared here already but devm will
remove the interrupt only a little later.
Thanks,
Wolfram
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