Re: [PATCH] i2c: imx: check busy bit when START/STOP

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Hi Richard,


On Tue, Sep 29, 2009 at 07:41:44PM +0800, Richard Zhao wrote:
> After START, wait busy bit to be set and
> after STOP, wait busy bit to be clear.
> 
> Disable clock when it's possible to save power.
> 
> Signed-off-by: Richard Zhao <linuxzsc@xxxxxxxxx>
> ---
>  drivers/i2c/busses/i2c-imx.c |  116 ++++++++++++++++++++++++++++++++----------
>  1 files changed, 88 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 4afba3e..59cde70 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -120,19 +120,40 @@ struct imx_i2c_struct {
>  	wait_queue_head_t	queue;
>  	unsigned long		i2csr;
>  	unsigned int 		disable_delay;
> +	unsigned int		ifdr; /* IMX_I2C_IFDR */
>  };
> 
>  /** Functions for IMX I2C adapter driver
> ***************************************
>  *******************************************************************************/
> 
> -static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx)
> +#ifdef CONFIG_I2C_DEBUG_BUS
> +#define reg_dump(i2c_imx) \
> +{ \
> +	printk(KERN_DEBUG "fun %s:%d ", __func__, __LINE__); \
> +	printk(KERN_DEBUG "IADR %02x IFDR %02x I2CR %02x I2SR %02x\n", \
> +		readb(i2c_imx->base + IMX_I2C_IADR), \
> +		readb(i2c_imx->base + IMX_I2C_IFDR), \
> +		readb(i2c_imx->base + IMX_I2C_I2CR), \
> +		readb(i2c_imx->base + IMX_I2C_I2SR)); \
> +}
> +#else
> +#define reg_dump(i2c_imx)
> +#endif
> +

Can you please remove this reg_dump? If we really need this it should be
in an extra patch and not clutter this one.

> +static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy)
>  {
>  	unsigned long orig_jiffies = jiffies;
> +	unsigned int temp;
> 
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
> 
>  	/* wait for bus not busy */

This comment seems wrong now. This function waits for busy or not busy
depending on for_busy.

> -	while (readb(i2c_imx->base + IMX_I2C_I2SR) & I2SR_IBB) {
> +	temp = readb(i2c_imx->base + IMX_I2C_I2SR);
> +	while (1) {
> +		if (for_busy && (temp & I2SR_IBB))
> +			break;
> +		if (!for_busy && !(temp & I2SR_IBB))
> +			break;
>  		if (signal_pending(current)) {
>  			dev_dbg(&i2c_imx->adapter.dev,
>  				"<%s> I2C Interrupted\n", __func__);
> @@ -141,9 +162,11 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx)
>  		if (time_after(jiffies, orig_jiffies + HZ / 1000)) {
>  			dev_dbg(&i2c_imx->adapter.dev,
>  				"<%s> I2C bus is busy\n", __func__);
> +			reg_dump(i2c_imx);
>  			return -EIO;
>  		}
>  		schedule();
> +		temp = readb(i2c_imx->base + IMX_I2C_I2SR);
>  	}
> 
>  	return 0;
> @@ -158,9 +181,11 @@ static int i2c_imx_trx_complete(struct
> imx_i2c_struct *i2c_imx)
> 
>  	if (unlikely(result < 0)) {
>  		dev_dbg(&i2c_imx->adapter.dev, "<%s> result < 0\n", __func__);
> +		reg_dump(i2c_imx);
>  		return result;
>  	} else if (unlikely(!(i2c_imx->i2csr & I2SR_IIF))) {
>  		dev_dbg(&i2c_imx->adapter.dev, "<%s> Timeout\n", __func__);
> +		reg_dump(i2c_imx);
>  		return -ETIMEDOUT;
>  	}
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s> TRX complete\n", __func__);
> @@ -172,6 +197,7 @@ static int i2c_imx_acked(struct imx_i2c_struct *i2c_imx)
>  {
>  	if (readb(i2c_imx->base + IMX_I2C_I2SR) & I2SR_RXAK) {
>  		dev_dbg(&i2c_imx->adapter.dev, "<%s> No ACK\n", __func__);
> +		reg_dump(i2c_imx);
>  		return -EIO;  /* No ACK */
>  	}
> 
> @@ -179,20 +205,37 @@ static int i2c_imx_acked(struct imx_i2c_struct *i2c_imx)
>  	return 0;
>  }
> 
> -static void i2c_imx_start(struct imx_i2c_struct *i2c_imx)
> +static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)
>  {
>  	unsigned int temp = 0;
> +	int result;
> 
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
> 
> +	clk_enable(i2c_imx->clk);
> +	writeb(i2c_imx->ifdr, i2c_imx->base + IMX_I2C_IFDR);
>  	/* Enable I2C controller */
> +	writeb(0, i2c_imx->base + IMX_I2C_I2SR);
>  	writeb(I2CR_IEN, i2c_imx->base + IMX_I2C_I2CR);
> +
> +	result = i2c_imx_bus_busy(i2c_imx, 0);
> +	if (result) {
> +		reg_dump(i2c_imx);
> +		return result;
> +	}
> +
>  	/* Start I2C transaction */
>  	temp = readb(i2c_imx->base + IMX_I2C_I2CR);
>  	temp |= I2CR_MSTA;
>  	writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
> +	result = i2c_imx_bus_busy(i2c_imx, 1);
> +	if (result) {
> +		reg_dump(i2c_imx);
> +		return result;
> +	}
>  	temp |= I2CR_IIEN | I2CR_MTX | I2CR_TXAK;
>  	writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
> +	return result;
>  }
> 
>  static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx)
> @@ -202,18 +245,21 @@ static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx)
>  	/* Stop I2C transaction */
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
>  	temp = readb(i2c_imx->base + IMX_I2C_I2CR);
> -	temp &= ~I2CR_MSTA;
> +	temp &= ~(I2CR_MSTA | I2CR_MTX);

This change seems unrelated. Is it necessary?

>  	writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
> -	/* setup chip registers to defaults */
> -	writeb(I2CR_IEN, i2c_imx->base + IMX_I2C_I2CR);
> -	writeb(0, i2c_imx->base + IMX_I2C_I2SR);
>  	/*
>  	 * This delay caused by an i.MXL hardware bug.
>  	 * If no (or too short) delay, no "STOP" bit will be generated.
>  	 */
>  	udelay(i2c_imx->disable_delay);
> +
> +

double blank line

> +	if (i2c_imx_bus_busy(i2c_imx, 0))
> +		reg_dump(i2c_imx);
> +
>  	/* Disable I2C controller */
>  	writeb(0, i2c_imx->base + IMX_I2C_I2CR);
> +	clk_disable(i2c_imx->clk);
>  }
> 
>  static void __init i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
> @@ -233,17 +279,19 @@ static void __init i2c_imx_set_clk(struct
> imx_i2c_struct *i2c_imx,
>  	else
>  		for (i = 0; i2c_clk_div[i][0] < div; i++);
> 
> -	/* Write divider value to register */
> -	writeb(i2c_clk_div[i][1], i2c_imx->base + IMX_I2C_IFDR);

Why can't we write this value directly anymore...

> -
> -	/*
> -	 * There dummy delay is calculated.
> -	 * It should be about one I2C clock period long.
> -	 * This delay is used in I2C bus disable function
> -	 * to fix chip hardware bug.
> -	 */
> -	i2c_imx->disable_delay = (500000U * i2c_clk_div[i][0]
> -		+ (i2c_clk_rate / 2) - 1) / (i2c_clk_rate / 2);
> +	/* Store divider value */
> +	i2c_imx->ifdr = i2c_clk_div[i][1];

...but have to store it in a variable instead?

> +
> +	if (cpu_is_mx1()) {
> +		/*
> +		 * There dummy delay is calculated.
> +		 * It should be about one I2C clock period long.
> +		 * This delay is used in I2C bus disable function
> +		 * to fix chip hardware bug.
> +		 */
> +		i2c_imx->disable_delay = (500000U * i2c_clk_div[i][0]
> +			+ (i2c_clk_rate / 2) - 1) / (i2c_clk_rate / 2);
> +	}
> 
>  	/* dev_dbg() can't be used, because adapter is not yet registered */
>  #ifdef CONFIG_I2C_DEBUG_BUS
> @@ -344,7 +392,7 @@ static int i2c_imx_read(struct imx_i2c_struct
> *i2c_imx, struct i2c_msg *msgs)
>  			dev_dbg(&i2c_imx->adapter.dev,
>  				"<%s> clear MSTA\n", __func__);
>  			temp = readb(i2c_imx->base + IMX_I2C_I2CR);
> -			temp &= ~I2CR_MSTA;
> +			temp &= ~(I2CR_MSTA | I2CR_MTX);
>  			writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
>  		} else if (i == (msgs->len - 2)) {
>  			dev_dbg(&i2c_imx->adapter.dev,
> @@ -369,14 +417,24 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>  	struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(adapter);
> 
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
> -
> +#ifdef CONFIG_I2C_DEBUG_BUS
> +	for (i = 0; i < num; i++) {
> +		printk(KERN_DEBUG "msg%d addr %02x RD %d cnt %d d:", i,
> +			msgs[i].addr, msgs[i].flags & I2C_M_RD, msgs[i].len);
> +		if (!(msgs[i].flags & I2C_M_RD)) {
> +			int j;
> +			for (j = 0; j < msgs[i].len; j++)
> +				printk("%02x ", msgs[i].buf[j]);
> +		}
> +		printk("\n");
> +	}
> +#endif
>  	/* Check if i2c bus is not busy */
> -	result = i2c_imx_bus_busy(i2c_imx);
> -	if (result)
> -		goto fail0;

When removing the code you should also remove the comment.

> 
>  	/* Start I2C transfer */
> -	i2c_imx_start(i2c_imx);
> +	result = i2c_imx_start(i2c_imx);
> +	if (result)
> +		goto fail0;
> 
>  	/* read/write data */
>  	for (i = 0; i < num; i++) {
> @@ -386,6 +444,11 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>  			temp = readb(i2c_imx->base + IMX_I2C_I2CR);
>  			temp |= I2CR_RSTA;
>  			writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
> +			result =  i2c_imx_bus_busy(i2c_imx, 1);
> +			if (result) {
> +				reg_dump(i2c_imx);
> +				goto fail0;
> +			}
>  		}
>  		dev_dbg(&i2c_imx->adapter.dev,
>  			"<%s> transfer message: %d\n", __func__, i);
> @@ -442,7 +505,7 @@ static int __init i2c_imx_probe(struct
> platform_device *pdev)
>  	int irq;
>  	int ret;
> 
> -	dev_dbg(&pdev->dev, "<%s>\n", __func__);
> +	dev_info(&pdev->dev, "<%s>\n", __func__);

no

> 
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	if (!res) {
> @@ -500,7 +563,6 @@ static int __init i2c_imx_probe(struct
> platform_device *pdev)
>  		dev_err(&pdev->dev, "can't get I2C clock\n");
>  		goto fail3;
>  	}
> -	clk_enable(i2c_imx->clk);

I think it's generally a good idea to start/stop the clocks when needed
as you do here. It should be an extra patch though.

> 
>  	/* Request IRQ */
>  	ret = request_irq(i2c_imx->irq, i2c_imx_isr, 0, pdev->name, i2c_imx);
> @@ -549,7 +611,6 @@ static int __init i2c_imx_probe(struct
> platform_device *pdev)
>  fail5:
>  	free_irq(i2c_imx->irq, i2c_imx);
>  fail4:
> -	clk_disable(i2c_imx->clk);
>  	clk_put(i2c_imx->clk);
>  fail3:
>  	release_mem_region(i2c_imx->res->start, resource_size(res));
> @@ -587,7 +648,6 @@ static int __exit i2c_imx_remove(struct
> platform_device *pdev)
>  		pdata->exit(&pdev->dev);
> 
>  	/* Disable I2C clock */
> -	clk_disable(i2c_imx->clk);
>  	clk_put(i2c_imx->clk);
> 
>  	release_mem_region(i2c_imx->res->start, resource_size(i2c_imx->res));
> -- 
> 1.6.0.4
> 

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