Freescale Linux BSP review

[Jammy Zhou]

On Tue, Dec 14, 2010 at 10:06 AM, Jerome Glisse <j.glisse at gmail.com> wrote:

> On Mon, Dec 13, 2010 at 9:04 PM, Jammy Zhou <jammy.zhou at linaro.org> wrote:
> >
> >
> > On Tue, Dec 14, 2010 at 12:11 AM, Jerome Glisse <j.glisse at gmail.com>
> wrote:
> >>
> >> On Mon, Dec 13, 2010 at 10:18 AM, Arnd Bergmann <arnd at arndb.de> wrote:
> >> > On Monday 13 December 2010, Jammy Zhou wrote:
> >> >> On Mon, Dec 13, 2010 at 4:45 AM, Linus Walleij
> >> >> <linus.walleij at linaro.org>wrote:
> >> >>
> >> >> > On 11 December 2010 22:41, Arnd Bergmann <arnd at arndb.de> wrote:
> >> >> >
> >> >> > * amd-gpu -- a single but huge driver for the GPU. As is normally
> the
> >> >> >>             case with GPU drivers, we can expect long discussions
> >> >> >>             before it will get considered for mainline
> >> >> >>  4 patches
> >> >> >>  98 files changed, 278321 insertions(+), 0 deletions(-)
> >> >> >>
> >> >> >
> >> >> > Just out of curiosity, following the discussion between Dave Airlie
> >> >> > and Codeaurora this summer re GPU driver shims.
> >> >> >
> >> >> > Is the AMD GPU exposing all functionality in its kernel driver or
> >> >> > is there some userspace blob somewhere with lots of e.g. GL
> >> >> > goodies?
> >> >> >
> >> >> All the functionality for the kernel driver of AMD GPU Z430/Z160 (now
> >> >> belongs to Qualcom) is exposed. But we need accompanied userspace
> >> >> library to
> >> >> call these functionality (buffer management, command submission,
> ...).
> >> >
> >> > Who owns these components? If it's closed source, the only options we
> >> > have are lobbying for complete release of the specs for a
> >> > reimplementation
> >> > or reverse-engineering the drivers, which may at least get easier with
> >> > a user space driver than it would be with a kernel driver.
> >> >
> >> > Until there is a solution with an open source user space part, I would
> >> > suggest that the driver better be dropped from the Freescale BSP and
> >> > we should at least not waste time reviewing it.
> >> >
> >> >        Arnd
> >>
> >> From a quick look it also seems that the API exposed to userspace
> >> would allow easy abuse of the GPU to access any system ram. There is a
> >> reason we do expensive command checking in the other amd gpu driver
> >> (drivers/gpu/drm/radeon/*cs.c files)
> >
> > No, the memory used by the GPU is reserved at boot time, so I think there
> is
> > no such a problem.
> >
> >>
> >> Cheers,
> >> Jerome
> >
> >
>
> This isn't about what's reserved, this is about GPU capacity, if the
> GPU is isolated through an IOMMU and the GPU can't reprogram it then
> fine. But if not, then it's easy to abuse packet to reprogram the GPU
> GART (either by reprogramming GART register or by overwritting GART
> table) to point to any system ram.
>

For non-PCI GPU in embedded world, there is no GART concept. Besides, the
GPU MMU is disabled currently for some hardware problem.


>
> Cheers,
> Jerome
>
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