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SubjectRe: [PATCH] of/base: Fix PowerPC address parsing hack
On Thu, Nov 13, 2014 at 12:45 AM, Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
> What about this one instead ? I want to cache it because that function
> can be called quite a while and doing two additional property lookup
> and string compares every time might hurt some platforms.
>
> ----
>
> We have a historical hack that treats missing ranges properties as the
> equivalent of an empty one. This is needed for ancient PowerMac "bad"
> device-trees, and shouldn't be enabled for any other PowerPC platform,
> otherwise we get some nasty layout of devices in sysfs or even
> duplication when a set of otherwise identically named devices is
> created multiple times under a different parent node with no ranges
> property.
>
> This fix is needed for the PowerNV i2c busses to be exposed properly
> and will fix a number of other embedded cases.
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: <stable@vger.kernel.org>

How far back does this need to go? I assume I need to get this in for v3.18.

>
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index e371825..5eae0cd 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -403,6 +403,17 @@ static struct of_bus *of_match_bus(struct device_node *np)
> return NULL;
> }
>
> +static int of_empty_ranges_quirk(void)
> +{
> + /* To save cycles, we cache the result */
> + static int quirk_state = -1;
> +

if (IS_ENABLED(CONFIG_POWERPC)) {

> + if (quirk_state < 0)
> + quirk_state = of_machine_is_compatible("Power Macintosh") ||
> + of_machine_is_compatible("MacRISC");
> + return quirk_state;

}
return 0;

So it gets compiled out for non powerpc.

> +}
> +
> static int of_translate_one(struct device_node *parent, struct of_bus *bus,
> struct of_bus *pbus, __be32 *addr,
> int na, int ns, int pna, const char *rprop)
> @@ -428,12 +439,10 @@ static int of_translate_one(struct device_node *parent, struct of_bus *bus,
> * This code is only enabled on powerpc. --gcl
> */
> ranges = of_get_property(parent, rprop, &rlen);
> -#if !defined(CONFIG_PPC)
> - if (ranges == NULL) {
> + if (ranges == NULL && !of_empty_ranges_quirk()) {
> pr_err("OF: no ranges; cannot translate\n");
> return 1;
> }
> -#endif /* !defined(CONFIG_PPC) */
> if (ranges == NULL || rlen == 0) {
> offset = of_read_number(addr, na);
> memset(addr, 0, pna * 4);
>
>


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