Re: [PATCH v2] powerpc/5200: tighten up ac97 reset timing

[Grant Likely <grant.likely@secretlab.ca>]

On Fri, Sep 03, 2010 at 01:27:38PM -0400, Eric Millbrandt wrote:
> Tighten up time timing around the gpio reset functionality.  Add a 200ns
> delay before remuxing the pins back to ac97 to comply with the ac97 spec.
> 
> Signed-off-by: Eric Millbrandt <emillbrandt@dekaresearch.com>
> ---
> 
> Scope shots availible upon request
> 
> changes since v1
> - amended with comments from Wolfram Sang
> 
>  arch/powerpc/platforms/52xx/mpc52xx_common.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)

Applied, but the patch was mangled (tabs->spaces) and I had to fix it
up by hand.  You'll need to find a way to get out from under your
corporate email manging server.

g.

> 
> diff --git a/arch/powerpc/platforms/52xx/mpc52xx_common.c b/arch/powerpc/platforms/52xx/mpc52xx_common.c
> index 6e90531..41f3a7e 100644
> --- a/arch/powerpc/platforms/52xx/mpc52xx_common.c
> +++ b/arch/powerpc/platforms/52xx/mpc52xx_common.c
> @@ -325,12 +325,16 @@ int mpc5200_psc_ac97_gpio_reset(int psc_number)
>         clrbits32(&simple_gpio->simple_dvo, sync | out);
>         clrbits8(&wkup_gpio->wkup_dvo, reset);
> 
> -       /* wait at lease 1 us */
> -       udelay(2);
> +       /* wait for 1 us */
> +       udelay(1);
> 
>         /* Deassert reset */
>         setbits8(&wkup_gpio->wkup_dvo, reset);
> 
> +       /* wait at least 200ns */
> +       /* 7 ~= (200ns * timebase) / ns2sec */
> +       __delay(7);
> +
>         /* Restore pin-muxing */
>         out_be32(&simple_gpio->port_config, mux);
> 
> --
> 1.6.3.1
> 
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