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The reworked MPU code produces a new warning in some configurations,
presumably starting with the code move after the compiler now makes
different inlining decisions:
arch/arm/mm/pmsa-v7.c: In function 'adjust_lowmem_bounds_mpu':
arch/arm/mm/pmsa-v7.c:310:5: error: 'specified_mem_size' may be used uninitialized in this function [-Werror=maybe-uninitialized]
This appears to be harmless, as we know that there is always at
least one memblock, and the only way this could get triggered is
if the for_each_memblock() loop was never entered.
I could not come up with a better workaround than initializing
the specified_mem_size to zero, but at least that is the value
that the variable would have in the hypothetical case of no
memblocks.
Fixes: 877ec119dbbf ("ARM: 8706/1: NOMMU: Move out MPU setup in separate module")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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Currently, there is assumption in early MPU setup code that kernel
image is located in RAM, which is obviously not true for XIP. To run
code from ROM we need to make sure that it is covered by MPU. However,
due to we allocate regions (semi-)dynamically we can run into issue of
trimming region we are running from in case ROM spawns several MPU
regions. To help deal with that we enforce minimum alignments for start
end end of XIP address space as 1MB and 128Kb correspondingly.
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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PMSAv7 defines curious alignment requirements to the regions:
- size must be power of 2, and
- region start must be aligned to the region size
Because of that we currently adjust lowmem bounds plus we assign
only one MPU region to cover memory all these lead to significant amount of
memory could be wasted. As an example, consider 64Mb of memory at
0x70000000 - it fits alignment requirements nicely; now, imagine that
2Mb of memory is reserved for coherent DMA allocation, so now Linux is
expected to see 62Mb of memory... and here annoying thing happens -
memory gets truncated to 32Mb (we've lost 30Mb!), i.e. MPU layout
looks like:
0: base 0x70000000, size 0x2000000
This patch tries to allocate as much as possible MPU slots to minimise
amount of truncated memory. Moreover, with this patch MPU subregions
starting to get used. MPU subregions allow us reduce the number of MPU
slots used. For example given above, MPU layout looks like:
0: base 0x70000000, size 0x2000000
1: base 0x72000000, size 0x1000000
2: base 0x73000000, size 0x1000000, disable subreg 7 (0x73e00000 - 0x73ffffff)
Where without subregions we'd get:
0: base 0x70000000, size 0x2000000
1: base 0x72000000, size 0x1000000
2: base 0x73000000, size 0x800000
3: base 0x73800000, size 0x400000
4: base 0x73c00000, size 0x200000
To achieve better layout we fist try to cover specified memory as is
(maybe with help of subregions) and if we failed, we truncate memory
to fit alignment requirements (so it occupies one MPU slot) and
perform one more attempt with the reminder, and so on till we either
cover all memory or run out of MPU slots.
Tested-by: Szemző András <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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This patch makes it possible to use MPU with v7M cores.
Tested-by: Szemző András <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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Currently, there are several issues with how MPU is setup:
1. We won't boot if MPU is missing
2. We won't boot if use XIP
3. Further extension of MPU setup requires asm skills
The 1st point can be relaxed, so we can continue with boot CPU even if
MPU is missed and fail boot for secondaries only. To address the 2nd
point we could create region covering CONFIG_XIP_PHYS_ADDR - _end and
that might work for the first stage of MPU enable, but due to MPU's
alignment requirement we could cover too much, IOW we need more
flexibility in how we're partitioning memory regions... and it'd be
hardly possible to archive because of the 3rd point.
This patch is trying to address 1st and 3rd issues and paves the path
for 2nd and further improvements.
The most visible change introduced with this patch is that we start
using mpu_rgn_info array (as it was supposed?), so change in MPU setup
done by boot CPU is recorded there and feed to secondaries. It
allows us to keep minimal region setup for boot CPU and do the rest in
C. Since we start programming MPU regions in C evaluation of MPU
constrains (number of regions supported and minimal region order) can
be done once, which in turn open possibility to free-up "probe"
region early.
Tested-by: Szemző András <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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Currently, inline assembly for accessing to MPU's cp15 lacks volatile
keyword which opens possibility to compiler to optimise such accesses
as soon as we start using them more intensively. Rather than fixing
inline asm, lets move MPU accessors to use cp15 helpers which do the
right thing.
Tested-by: Szemző András <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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Having MPU handling code in dedicated module makes it easier to
enhance/maintain it.
Tested-by: Szemző András <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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