On 09/10/18 05:53, Rob Herring wrote: > On Sun, Sep 09, 2018 at 07:04:25PM +0200, Benjamin Herrenschmidt wrote: >> On Fri, 2018-08-31 at 14:58 +1000, Benjamin Herrenschmidt wrote: >>> >>>> A long shot, but something to consider, is that I failed to cover the >>>> cases of dynamic devicetree updates (removing nodes that contain a >>>> phandle) in ways other than overlays. Michael Ellerman has reported >>>> such a problem for powerpc/mobility with of_detach_node(). A patch to >>>> fix that is one of the tasks I need to complete. >>> >>> The only thing I can think of is booting via the BootX bootloader on >>> those ancient macs results in a DT with no phandles. I didn't see an >>> obvious reason why that would cause that patch to break though. >> >> Guys, we still don't have a fix for this one on its way upstream... >> >> My test patch just creates phandle properties for all nodes, that was >> not intended as a fix, more a way to check if the problem was related >> to the lack of phandles. >> >> I don't actually know why the new code causes things to fail when >> phandles are absent. This needs to be looked at. >> >> I'm travelling at the moment and generally caught up with other things, >> I haven't had a chance to dig, so just a heads up. I don't intend to >> submit my patch since it's just a band aid. We need to figure out what >> the actual problem is. > > Can you try this patch (w/o Ben's patch). I think the problem is if > there are no phandles, then roundup_pow_of_two is passed 0 which is > documented as undefined result. > > Though, if a DT has no properties with phandles, then why are we doing a > lookup in the first place? > > > 8<---------------------------------------------------------------------- > > diff --git a/drivers/of/base.c b/drivers/of/base.c > index 9095b8290150..74eaedd5b860 100644 > --- a/drivers/of/base.c > +++ b/drivers/of/base.c > @@ -140,6 +140,9 @@ void of_populate_phandle_cache(void) > if (np->phandle && np->phandle != OF_PHANDLE_ILLEGAL) > phandles++; > > + if (!phandles) > + goto out; > + > cache_entries = roundup_pow_of_two(phandles); > phandle_cache_mask = cache_entries - 1; > > Thanks Rob! That fix makes sense, and the test results look promising. Reviewed-by: Frank Rowand <frank.rowand@xxxxxxxx>
