Re: [PATCH v4 3/5] powerpc/mpc5121: shared DIU framebuffer support

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On Fri, Jul 23, 2010 at 9:00 AM, Anatolij Gustschin <agust@xxxxxxx> wrote:

> @@ -1471,7 +1476,9 @@ static int __devinit fsl_diu_probe(struct of_device *ofdev,
>                goto error2;
>        }
>
> -       out_be32(&dr.diu_reg->diu_mode, 0);             /* disable DIU anyway*/
> +       diu_mode = in_be32(&dr.diu_reg->diu_mode);
> +       if (diu_mode != MFB_MODE1)
> +               out_be32(&dr.diu_reg->diu_mode, 0);     /* disable DIU */

Anatolij,

I know this patch is old, but I just noticed something odd about it
that I need your help with.

In the above snippet, you test for != MFB_MODE1.  My understanding is
that U-boot only supports modes 0 and 1, never modes 2 or 3.  So
diu_mode can only ever be 0 or 1.  That means that that the above code
is equivalent to:

diu_mode = in_be32(&dr.diu_reg->diu_mode);
if (diu_mode == 0)
        out_be32(&dr.diu_reg->diu_mode, 0);     /* disable DIU */

which is silly, because now we're writing 0 to diu_mode only if it's already 0.

Am I missing something?

-- 
Timur Tabi
Linux kernel developer at Freescale
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