Hi Ben,
On Thu, 29 May 2008 14:22:48 +0100, Ben Dooks wrote:
> Add a single-master option to drasitcally reduce the time spent
> waiting to check the bus is free and ready for another transfer.
I don't understand. If you have a single-master bus, then the bus can
simply never be busy when you attempt to start a transaction. So, the
timeout setting shouldn't change anything, as you will get the bus
immediately anyway. Isn't it the case?
As a side note, this timeout loop is pretty broken anyway, as it
depends on the value of HZ. It should be adjusted to be time-based
rather than count-based.
>
> Signed-off-by: Ben Dooks <[EMAIL PROTECTED]>
>
> Index: linux-2.6.26-rc4-quilt2/drivers/i2c/busses/i2c-s3c2410.c
> ===================================================================
> --- linux-2.6.26-rc4-quilt2.orig/drivers/i2c/busses/i2c-s3c2410.c
> 2008-05-28 12:27:38.000000000 +0100
> +++ linux-2.6.26-rc4-quilt2/drivers/i2c/busses/i2c-s3c2410.c 2008-05-28
> 12:32:10.000000000 +0100
> @@ -472,8 +472,15 @@ static irqreturn_t s3c24xx_i2c_irq(int i
>
> static int s3c24xx_i2c_set_master(struct s3c24xx_i2c *i2c)
> {
> + struct s3c2410_platform_i2c *pdata;
> unsigned long iicstat;
> - int timeout = 400;
> + int timeout;
> +
> + /* if we are a single master on this bus, reduce the delay awaiting
> + * for bus traffic to a much lower value. */
> +
> + pdata = s3c24xx_i2c_get_platformdata(i2c->dev);
> + timeout = (pdata->flags & S3C_IICFLG_SINGLE_MASTER) ? 10 : 400;
>
> while (timeout-- > 0) {
> iicstat = readl(i2c->regs + S3C2410_IICSTAT);
> Index: linux-2.6.26-rc4-quilt2/include/asm-arm/plat-s3c/iic.h
> ===================================================================
> --- linux-2.6.26-rc4-quilt2.orig/include/asm-arm/plat-s3c/iic.h
> 2008-05-28 12:28:00.000000000 +0100
> +++ linux-2.6.26-rc4-quilt2/include/asm-arm/plat-s3c/iic.h 2008-05-28
> 12:32:10.000000000 +0100
> @@ -13,7 +13,8 @@
> #ifndef __ASM_ARCH_IIC_H
> #define __ASM_ARCH_IIC_H __FILE__
>
> -#define S3C_IICFLG_FILTER (1<<0) /* enable s3c2440 filter */
> +#define S3C_IICFLG_FILTER (1<<0) /* enable s3c2440 filter */
> +#define S3C_IICFLG_SINGLE_MASTER (1<<1) /* s3c24xx is only bus master. */
>
> /* Notes:
> * 1) All frequencies are expressed in Hz
>
--
Jean Delvare
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