[PATCH] ARM: shmobile: Include all 2 GiB of memory on APE6EVM

[Simon Horman]

On Wed, Nov 06, 2013 at 06:48:45PM +0900, Magnus Damm wrote:
> Hi Simon,
> 
> On Wed, Nov 6, 2013 at 10:48 AM, Simon Horman <horms at verge.net.au> wrote:
> > On Thu, Oct 31, 2013 at 05:02:13PM +0900, Magnus Damm wrote:
> >> Hi Simon,
> >>
> >> On Thu, Oct 31, 2013 at 1:20 PM, Simon Horman <horms at verge.net.au> wrote:
> >> > On Thu, Oct 31, 2013 at 12:15:49PM +0900, Magnus Damm wrote:
> >> >> From: Takashi Yoshii <takasi-y at ops.dti.ne.jp>
> >> >>
> >> >> Add 1GiB of DRAM at 0x2_0000_0000 to support the full 2GiB
> >> >> of APE6EVM system memory.
> >> >>
> >> >> Signed-off-by: Takashi Yoshii <takasi-y at ops.dti.ne.jp>
> >> >> Signed-off-by: Magnus Damm <damm at opensource.se>
> >> >> ---
> >> >>
> >> >>  For correct run time operation regardless of kernel configuration
> >> >>  ARM patches 7863/1 and 7864/1 are needed.
> >> >
> >> > I take it that I should wait for those patches before applying this one.
> >>
> >> That's probably a good idea. RMK has applied them to "git-curr", so I
> >> suppose they are queued up for something at least:
> >>
> >> http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=7863/1
> >
> > I have also sighted them in linux-next.
> > So I expect they will show up in v3.13-rc1 or thereabouts.
> >
> >> > With those two patches and this one applied on top of
> >> > renesas-devel-v3.12-rc7-20131030 I was able to successfully
> >> > boot an ape6evm board. But /proc/meminfo still indicates only 1Gb of
> >> > memory. What am I missing.
> >>
> >> You probably need to enable HIGHMEM and LPAE to be able to access to
> >> all memory. Same thing on Lager, to get the full 4GiB you need to
> >> select those in your kernel configuration too.
> >
> > Thanks, I have been able to successfully test all 4 patches in this
> > series with those settings enabled.
> >
> > Tested-by: Simon Horman <horms+renesas at verge.net.au>
> >
> >> Please note that having memory located on 64-bit addresses may break
> >> some drivers doing bus mastering or using the DMAC. These drivers need
> >> to be fixed both with short term DMA zone workarounds and proper
> >> 64-bit address support whenever possible.
> >>
> >> So if I could suggest a policy then having LPAE=n in defconfig for the
> >> C board code for default stable operation. This together with LPAE=y
> >> in the case of DT reference and/or Multiplatform where we can be a bit
> >> more experimental. I don't care enough to send defconfig patches, but
> >> if some issue comes up then perhaps adjusting the defconfig to disable
> >> LPAE may work well as a workaround.
> >
> > Thanks.
> >
> > As it stands the defconfig for both APE6EVM and Lager lead to a
> > configuration with LPAE disabled, although neither explicitly disable LPAE.
> > I think it is best to leave things as-is in this regards and explicitly
> > disable LPAE in the defconfigs if the need arises.
> >
> > While looking over this I noticed that the APE6EVM defconfig selects
> > HIGHMEM while the Lager defconfig does not and it is not selected in the
> > resulting config. Would it be worth updating the Lager defconfig to enable
> > HIGHMEM? If so, I'll make a patch.
> 
> Thanks. I think it mainly makes sense to enable LPAE and HIGHMEM
> together, so easiest is probably just to wait with both Lager and
> APE6EVM.

Sure. I will immediately do nothing :)