[U-Boot] [PATCH 1/2] arm: Replace test for CONFIG_ARMV7 with CONFIG_CPU_V7

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hello Marek,

On Tue, 29 Dec 2015 19:44:01 +0100, Marek Vasut <marex@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.