Initial HIGHMEM support on ARC was introduced for PAE40 where the low
memory (0x8000_0000 based) and high memory (0x1_0000_0000) were
physically contiguous. So CONFIG_FLATMEM sufficed (despite a peipheral
hole in the middle, which wasted a bit of struct page memory, but things
worked).

However w/o PAE, highmem was not possible and we could only reach
~1.75GB of DDR. Now there is a use case to access ~4GB of DDR w/o PAE40
The idea is to have low memory at canonical 0x8000_0000 and highmem
at 0 so enire 4GB address space is available for physical addressing
This needs additional platform/interconnect mapping to convert
the non contiguous physical addresses into linear bus adresses.

From Linux point of view, non contiguous divide means FLATMEM no
longer works and DISCONTIGMEM is needed to track the pfns in the 2
regions.

This scheme would also work for PAE40, only better in that we don't
waste struct page memory for the peripheral hole.

The DT description will be something like

    memory {
        ...
        reg = <0x80000000 0x200000000   /* 512MB: lowmem */
               0x00000000 0x10000000>;  /* 256MB: highmem */
   }

Signed-off-by: Noam Camus <noamc@ezchip.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

So a benign looking cleanup which macro'ized PAGE_SHIFT shifts turned
out to be bad (since it was done non-sensically across the board).

It caused boot failures with PAE40 as forced cast to (unsigned long)
from newly introduced virt_to_pfn() was causing truncatiion of the
(long long) pte/paddr values.

It is OK to use this in accessors dealing with kernel virtual address,
pointers etc, but not for PTE values themelves.

Fixes: cJ2ff5cf2735c ("ARC: mm: Use virt_to_pfn() for addr >> PAGE_SHIFT pattern)
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

While reviewing a different change to asm-generic/io.h Arnd spotted that
ARC ioread32 and ioread32be both of which come from asm-generic versions
are not symmetrical in terms of calling the io barriers.

generic ioread32   -> ARC readl()                  [ has barriers]
generic ioread32be -> __be32_to_cpu(__raw_readl()) [ lacks barriers]

While generic ioread32be is being remediated to call readl(), that involves
a swab32(), causing double swaps on ioread32be() on Big Endian systems.

So provide our versions of big endian IO accessors to ensure io barrier
calls while also keeping them optimal

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: stable@vger.kernel.org  [4.2+]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

Enable reserved memory initialization from device tree.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

- The asm helpers for calling into irq tracer were missing

- Add calls to above helpers in low level assembly entry code for ARCv2

- irq_save() uses CLRI to disable interrupts and returns the prev interrupt
  state (in STATUS32) in a specific encoding (and not the raw value of
  STATUS32). This is usable with SETI in irq_restore(). However
  save_flags() reads the raw value of STATUS32 which doesn't pair with
  irq_save/restore() and thus needs fixing.

Signed-off-by: Evgeny Voevodin <evgeny.voevodin@intel.com>
[vgupta: updated changelog and also added some comments]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

Pull ARC fixes from Vineet Gupta:
 - fix Kconfig splat due to pcie rework
 - make ethernet work again on axs103
 - provide fb_pgprotect() for future video driver integration

* tag 'arc-4.6-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: [plat-axs103] Enable loop block devices
  Revert "ARC: [plat-axs10x] add Ethernet PHY description in .dts"
  arc: Add our own implementation of fb_pgprotect()
  ARC: Don't source drivers/pci/pcie/Kconfig ourselves

As mentioned in LTP's README.ARC:
------------->8------------
 Requirements for the environment

* Linux must be built with support of loop block devices. Thus it's
  necessary to enable these Linux kernel options:
  CONFIG_BLK_DEV
  CONFIG_BLK_DEV_LOOP
------------->8------------
enabling loop block devices.

That among other things lead to additional 10 fatal signals
appearing during LTP run.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

This reverts commit 667a490bdb6e27db0887d2ca515b907d6aa87118.

This is needed to get ethernet(stmmac) working in 4.6-rc2 on axs103.

4.5 needed this fix, but apprently stmmac has gained some fixes which
warrant reversal of this.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

During mmaping of frame-buffer pages to user-space
fb_protect() is called to set proper page settings.

In case of ARC we need to mark pages that are mmaped to
user as uncached because of 2 reasons:
 * Huge amount of data if passing through data cache will
   thrash cache a lot making cache almost useless for other
   less traffic hungry processes.
 * Data written by user in FB will be immediately available for
   hardware (such as PGU etc) without requirements to flush data
   cache regularly.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: linux-snps-arc@lists.infradead.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>