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The AM34 processor has an atomic operation that's the equivalent of LL/SC on
other architectures. However, rather than being done through a pair of
instructions, it's driven by writing to a pair of memory-mapped CPU control
registers.
One set of these registers (AARU/ADRU/ASRU) is available for use by userspace,
but for userspace to access them a PTE must be set up to cover the region.
This is done by dedicating the first vmalloc region page to this purpose,
setting the permissions on its PTE such that userspace can access the page.
glibc is hardcoded to expect the registers to be there.
The way atomic ops are done through these registers is straightforward:
(1) Write the address of the word you wish to access into AARU. This causes
the CPU to go and fetch that word and load it into ADRU. The status bits
are also cleared in ASRU.
(2) The current data value is read from the ADRU register and modified.
(3) To alter the data in RAM, the revised data is written back to the ADRU
register, which causes the CPU to attempt to write it back.
(4) The ASRU.RW flag (ASRU read watch), ASRU.LW flag (bus lock watch),
ASRU.IW (interrupt watch) and the ASRU.BW (bus error watch) flags then
must be checked to confirm that the operation wasn't aborted. If any of
the watches have been set to true, the operation was aborted.
Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
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Implement the Panasonic MN10300 AM34 CPU subarch and implement SMP support for
MN10300. Also implement support for the MN2WS0060 processor and the ASB2364
evaluation board which are AM34 based.
Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>
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Use the [ID]PTEL2 registers rather than [ID]PTEL for TLB control as the bits
are a more suitable layout.
Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>
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Since we no longer need to provide KM_type, the whole pte_*map_nested()
API is now redundant, remove it.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Miller <davem@davemloft.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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On VIVT ARM, when we have multiple shared mappings of the same file
in the same MM, we need to ensure that we have coherency across all
copies. We do this via make_coherent() by making the pages
uncacheable.
This used to work fine, until we allowed highmem with highpte - we
now have a page table which is mapped as required, and is not available
for modification via update_mmu_cache().
Ralf Beache suggested getting rid of the PTE value passed to
update_mmu_cache():
On MIPS update_mmu_cache() calls __update_tlb() which walks pagetables
to construct a pointer to the pte again. Passing a pte_t * is much
more elegant. Maybe we might even replace the pte argument with the
pte_t?
Ben Herrenschmidt would also like the pte pointer for PowerPC:
Passing the ptep in there is exactly what I want. I want that
-instead- of the PTE value, because I have issue on some ppc cases,
for I$/D$ coherency, where set_pte_at() may decide to mask out the
_PAGE_EXEC.
So, pass in the mapped page table pointer into update_mmu_cache(), and
remove the PTE value, updating all implementations and call sites to
suit.
Includes a fix from Stephen Rothwell:
sparc: fix fallout from update_mmu_cache API change
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Signed-off-by: David Howells <dhowells@redhat.com>
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