Re: [PATCH 4/4] i2c: imx: disable clock when it's possible to save power.

[Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

On Thu, Oct 01, 2009 at 09:13:33AM +0800, Richard Zhao wrote:
> Enable clock before START, disable it after STOP.

The clk_diable/enable calls in suspend/resume should be removed also.

Sascha

> 
> Signed-off-by: Richard Zhao <linuxzsc-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 87faea4..72ddea3 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -120,6 +120,7 @@ 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 ***************************************
> @@ -210,6 +211,8 @@ static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)
>  
>  	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);
> @@ -254,6 +257,7 @@ static void i2c_imx_stop(struct imx_i2c_struct *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,
> @@ -273,8 +277,8 @@ 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);
> +	/* Store divider value */
> +	i2c_imx->ifdr = i2c_clk_div[i][1];
>  
>  	if (cpu_is_mx1()) {
>  		/*
> @@ -555,7 +559,6 @@ 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);
>  
>  	/* Request IRQ */
>  	ret = request_irq(i2c_imx->irq, i2c_imx_isr, 0, pdev->name, i2c_imx);
> @@ -604,7 +607,6 @@ 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));
> @@ -641,8 +643,6 @@ static int __exit i2c_imx_remove(struct platform_device *pdev)
>  	if (pdata && pdata->exit)
>  		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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