[PATCH v2 08/27] drm/tegra: gr2d: Miscellaneous cleanups

[Terje Bergström]

On 07.10.2013 16:05, Erik Faye-Lund wrote:
> On Mon, Oct 7, 2013 at 2:52 PM, Terje Bergström <tbergstrom at nvidia.com> wrote:
>> AND 0xff is necessary, because the same registers are mirrored in
>> multiple contexts. AND removes the offset coming from context, and
>> leaves just the plain register offset.
> The offsets in the commands don't have enough bits to reach over to
> the next context. The contexts are repeated at multiples of 0x4000,
> and 0xFFF is the largest encodable offset. So I don't really thing the
> AND is needed for *that* purpose.

Well, that was embarrassing. Of course that is true. You can access all
registers via MMIO or with SETCLASS to correct context. But that was
still the reason I used when I wrote that 0xff, so it's bogus.

Real fix is to do what Thierry already did: limit the bitmap to max
register number we're interested in, and have a if() to fail fast if
register number falls outside that range.

Even better, get IOMMU up and running.

Terje