On Wed, 6 Aug 2014 17:02:44 -0500, Rob Herring <robherring2@xxxxxxxxx> wrote: > On Wed, Aug 6, 2014 at 3:30 PM, Al Cooper <alcooperx@xxxxxxxxx> wrote: > > __reserved_mem_reserve_reg() won't reserve memory if the base address > > is zero. This change removes the check for a base address of zero and > > allows it to be reserved. > > > > Allowing the first 4K of memory to be reserved will help solve a > > problem on some ARM systems where the the first 16K of memory is > > unused and becomes allocable memory. This will prevent this memory > > from being used for DMA by drivers like the USB OHCI driver which > > consider a physical address of zero to be illegal. > > OHCI driver or hardware? I agree with the change, but really think > this should be fixed in the driver in the former case or a property of > the OHCI node in the latter. I'm not hard and fast on that. I don't think it is unreasonable to reserve the base of memory as the platform level if there is a bug causing DMA to fail at that address. If this is a common problem (and not merely a few boards) then I agree. Fixing it this way is just asking for the same problem to show up again and again on new boards that haven't explicitly reserved the memory. g. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
