Re: [PATCH 2/4] i2c: imx: only imx1 needs disable delay

Sascha Hauer
2009-10-01T07:57:02Z

On Thu, Oct 01, 2009 at 03:52:15PM +0800, Richard Zhao wrote:
> On Thu, Oct 1, 2009 at 3:26 PM, Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
> > On Thu, Oct 01, 2009 at 09:13:31AM +0800, Richard Zhao wrote:
> >> check cpu_is_mx1() when set disable_delay.
> >>
> >> 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 156cc95..c1e541c 100644
> >> --- a/drivers/i2c/busses/i2c-imx.c
> >> +++ b/drivers/i2c/busses/i2c-imx.c
> >> @@ -254,14 +254,16 @@ static void __init i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
> >>       /* Write divider value to register */
> >>       writeb(i2c_clk_div[i][1], i2c_imx->base + IMX_I2C_IFDR);
> >>
> >> -     /*
> >> -      * 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);
> >> +     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);
> >> +     }
> >
> > I think you should put the udelay(i2c_imx->disable_delay) in
> > cpu_is_mx1() rather than the calculation.
> >
> > Sascha
> >
> >
> > --
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> >
> Do you think udelay(0) wast any more time than if()?

if (cpu_is_mx1()) is optimized out by the compiler.

Sascha

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