[Help][RS780E][mipsel]Screen corruption sometimes

Chen Jie chenj at lemote.com
Thu Aug 25 23:33:06 PDT 2011


2011/8/24 Alex Deucher <alexdeucher at gmail.com>

> On Wed, Aug 24, 2011 at 2:14 AM, Chen Jie <chenj at lemote.com> wrote:
> > Hi,
> >
> > 2011/8/23 Alex Deucher <alexdeucher at gmail.com>
> >>
> >> > Not sure I understand it or not, but we're using the sideport way, and
> >> > has a dedicated 128M DDR2 memory as VRAM.
> >>
> >> The default behavior of the system bios is to set up sideport memory
> >> interleaved with stolen system memory.  Unless your bios only enables
> >> sideport you'll need to respect the stolen system memory used as vram.
> >>  Also, sideport memory has really limited memory bandwidth.  It's a
> >> powersaving feature as if you un-interleave the sideport memory, you
> >> can put the display in sideport and stop memory access via the CPU.
> >> For decent performance, you need to use system memory or interleaved
> >> sideport and system memory.
> > Got it, thanks.
> > BTW, if using 128M sideport memory, will it occupy another 128M system
> > memory in the default behavior?
> >
> Yes.  Normally the sbios reports a slightly smaller ram size to
> account for the stolen memory or marks it as reserved so the OS
> doesn't try and use it.

We've checked the sbios setup code -- the setup logic is borrowed from
coreboot, and is confirmed using the single memory channel mode.

-- Chen Jie
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