Re: [PATCH v2 2/6] OMAP4: ID: add omap_has_feature for max freq supported

Menon, Nishanth
2011-08-04T23:34:14Z

On Fri, Jul 1, 2011 at 21:30, Rajendra Nayak <rnayak@ti.com> wrote:

[...]

> +static void __init omap4_check_features(void)
> +{
> +       u32 si_type;
> +
> +       if (cpu_is_omap443x())
> +               omap_features |= OMAP4_HAS_MPU_1GHZ;
> +
> +
> +       if (cpu_is_omap446x()) {
> +               si_type =
> +                       read_tap_reg(OMAP4_CTRL_MODULE_CORE_STD_FUSE_PROD_ID_1);
> +               switch ((si_type & (3 << 16)) >> 16) {
> +               case 2:
> +                       /* High performance device */
> +                       omap_features |= OMAP4_HAS_MPU_1_5GHZ;
> +                       break;
I have seen http://www.mail-archive.com/linux-omap@vger.kernel.org/msg51988.html
and I disagree with this.

We are setting up a standard for all future silicon that omap_features
if it contains a higher frequency will always support all lower
frequencies in omap_feature. This may be convinent for the moment,
BUT, I disagree with the approach as we cannot guarantee that this
will be the approach for all silica in the future and approach taken
here could be considered short-sighted. if 1.2GHz will be supported
then a check for omap_has_1_2GHz should be true as well - which this
patch will fail to support. E.g. on 4460 has_1GHz should'nt return
true as it is 920MHz, but the check for 1_2GHz should be true - which
it wont as return omap_features & OMAP3_HAS_ ##flag; will not have
BIT(9) set.

Regards,
Nishanth Menon
> +               case 1:
> +               default:
> +                       /* Standard device */
> +                       omap_features |= OMAP4_HAS_MPU_1_2GHZ;
> +                       break;
> +               }
> +       }
> +}
[...]
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