[U-Boot] [PATCH 1/2] arm: Replace test for CONFIG_ARMV7 with CONFIG_CPU_V7
Albert ARIBAUD
albert.u.boot at aribaud.net
Wed Dec 30 23:18:37 CET 2015
Hello Marek,
On Tue, 29 Dec 2015 19:44:01 +0100, Marek Vasut <marex at denx.de> wrote:
> The arch/arm/lib/cache-cp15.c checks for CONFIG_ARMV7 and if this macro is
> set, it configures TTBR0 register. This register must be configured for the
> cache on ARMv7 to operate correctly.
>
> The problem is that noone actually sets the CONFIG_ARMV7 macro and thus the
> TTBR0 is not configured at all. On SoCFPGA, this produces all sorts of minor
> issues which are hard to replicate, for example certain USB sticks are not
> detected or QSPI NOR sometimes fails to write pages completely.
>
> The solution is to replace CONFIG_ARMV7 test with CONFIG_CPU_V7 one. This is
> correct because the code which added the test(s) for CONFIG_ARMV7 was added
> shortly after CONFIG_ARMV7 was replaced by CONFIG_CPU_V7 and this code was
> not adjusted correctly to reflect that change.
Analysis of the series shows that:
- it does not change the values of DCACHE_OFF, DCACHE_WRITETHROUGH and
DCACHE_WRITEBACK;
- it does change the value of DCACHE_WRITEALLOC from 0x16 to 0x101E, but
DCACHE_WRITEALLOC is only used when CONFIG_SYS_ARM_CACHE_WRITEALLOC is
defined, which does not happen throughout U-Boot, as shown by a search
for "WRITEALLOC".
- it sets inner and outer region cache control bits in TTBR0, to match
the cacheability of the DDR in which the MMU table resides.
Marek performed tests of patch 1/2 only (with the S bit set) and of
the whole series (wih the S bit clear). With patch 1/2 only, Marek could
witness the performance hit described by Stefan Roese; with the whole
series, Marek saw no performance hit any more.
I will therefore take this patch series in, since it fixes an obvious
issue in the U-Boot code and does not show any adverse effect.
Amicalement,
--
Albert.
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