On 01/27/2015 09:15 AM, Thierry Reding wrote: > On Tue, Jan 27, 2015 at 07:07:44AM +0100, Thomas Hellstrom wrote: >> On 01/26/2015 11:51 PM, Dave Airlie wrote: >>> On 23 January 2015 at 18:05, Thierry Reding <thierry.reding@xxxxxxxxx> wrote: >>>> From: Thierry Reding <treding@xxxxxxxxxx> >>>> >>>> The current implementation is limited by the number of addresses that >>>> fit into an unsigned long. This causes problems on 32-bit Tegra where >>>> unsigned long is 32-bit but drm_mm is used to manage an IOVA space of >>>> 4 GiB. Given the 32-bit limitation, the range is limited to 4 GiB - 1 >>>> (or 4 GiB - 4 KiB for page granularity). >>>> >>>> This commit changes the start and size of the range to be an unsigned >>>> 64-bit integer, thus allowing much larger ranges to be supported. >>> This seems fine to me, Chris, Daniel or Thomas, any objections? >>> >>> Dave. >> >> This is perfectly fine with me, although I'm a bit curious why the >> allocation granularity of the IOVA space needs to be 1 byte? > > Are you referring to the 4 GiB - 1 comment? The point I was trying to > make is not that the granularity of the IOVA space needs to be 1 byte > but rather that using an unsigned long for a size on a 32-bit machine > will give you 4 GiB - 1 addresses. The IOMMU page size is still 4 KiB > for Tegra. I was rather referring to that if the range manager (drm_mm) is set up to manage pages instead of bytes (like, for example, the TTM VM address space), you'd get 4G - 1 pages, which, I believe, is sufficient on most 32 bit systems? Thanks, /Thomas > > Thierry _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
