Re: System hang when using SetMemoryAttributes

[Michael Zimmermann <sigmaepsilon92@gmail.com>]

I'm thankful for the hint about _WC because it drastically improves the
speed on my other devices.
Unfortunately, it doesn't fix the device I have problems with. I tested all
possible attributes and only EFI_MEMORY_WB seems to be
working(even EFI_MEMORY_WT is broken).

The weird thing is that even if I disable accesses to the framebuffer by
disabling all code in the Blt function, it hangs during boot.
I really can't explain this behavior.

On Mon, Sep 26, 2016 at 12:23 PM, Ard Biesheuvel <ard.biesheuvel@linaro.org>
wrote:

> On 26 September 2016 at 00:44, Michael Zimmermann
> <sigmaepsilon92@gmail.com> wrote:
> > oh and in case it makes a difference: it's a 64bit ARM device running
> 32bit
> > code.
> >
>
> That shouldn't matter.
>
> > On Mon, Sep 26, 2016 at 9:13 AM, Michael Zimmermann
> > <sigmaepsilon92@gmail.com> wrote:
> >>
> >> Ard,
> >>
> >> I have to mark the framebuffer as uncached, because if writes to it are
> >> cached, they don't instantly reach the underlying hardware. I'd have to
> >> manually flush the cache for that region every time otherwise.
> >>
> >> Isn't that the normal way? I don't think that any device would work
> with a
> >> write-cache framebuffer - I actually copied the code from the ArmVirt
> LCD
> >> drivers which do the same.
> >>
>
> _WC means write-combining, and so these accesses are not cacheable,
> but they do allow unaligned accesses, unlike _UC
>