[U-Boot] [PATCH v 1/3] arm: do not force d-cache enable on all boards

[Jason Liu]

2011/8/2 Jason Liu <liu.h.jason at gmail.com>:
> Hi, Aneesh,
>
> 2011/8/1 Aneesh V <aneesh at ti.com>:
>> c2dd0d45540397704de9b13287417d21049d34c6 added dcache_enable()
>> to board_init_r(). This enables d-cache for all ARM boards.
>> As a result some of the arm boards that are not cache-ready
>> are broken. Revert this change and allow platform code to
>> take the decision on d-cache enabling.
>>
>> Also add some documentation for cache usage in ARM.
>>
>> Signed-off-by: Aneesh V <aneesh at ti.com>
>> ---
>> MAKEALL pending. Will update the results tomorrow.
>> ---
>>  arch/arm/lib/board.c  |    8 +++-----
>>  arch/arm/lib/cache.c  |   12 ++++++++++++
>>  doc/README.arm-caches |   40 ++++++++++++++++++++++++++++++++++++++++
>>  include/common.h      |    1 +
>>  4 files changed, 56 insertions(+), 5 deletions(-)
>>  create mode 100644 doc/README.arm-caches
>>
>> diff --git a/arch/arm/lib/board.c b/arch/arm/lib/board.c
>> index 90709d0..d093d5b 100644
>> --- a/arch/arm/lib/board.c
>> +++ b/arch/arm/lib/board.c
>> @@ -446,11 +446,9 @@ void board_init_r (gd_t *id, ulong dest_addr)
>>        gd->flags |= GD_FLG_RELOC;      /* tell others: relocation done */
>>
>>        monitor_flash_len = _end_ofs;
>> -       /*
>> -        * Enable D$:
>> -        * I$, if needed, must be already enabled in start.S
>> -        */
>> -       dcache_enable();
>> +
>> +       /* Enable caches */
>> +       enable_caches();
>>
>>        debug ("monitor flash len: %08lX\n", monitor_flash_len);
>>        board_init();   /* Setup chipselects */
>> diff --git a/arch/arm/lib/cache.c b/arch/arm/lib/cache.c
>> index 92b61a2..b545fb7 100644
>> --- a/arch/arm/lib/cache.c
>> +++ b/arch/arm/lib/cache.c
>> @@ -53,3 +53,15 @@ void __flush_dcache_all(void)
>>  }
>>  void   flush_dcache_all(void)
>>        __attribute__((weak, alias("__flush_dcache_all")));
>> +
>> +
>> +/*
>> + * Default implementation of enable_caches()
>> + * Real implementation should be in platform code
>> + */
>> +void __enable_caches(void)
>> +{
>> +       puts("WARNING: Caches not enabled\n");
>> +}
>> +void enable_caches(void)
>> +       __attribute__((weak, alias("__enable_caches")));
>
>
> What about the following change?
>
> #ifndef CONFIG_SYS_DCACHE_OFF
>        dcache_enable();
> #else
>       puts("WARNING: Caches not enabled\n");
> #endif

Or better:

#ifdef CONFIG_SYS_DCACHE_ON
        dcache_enable();
 #else
       puts("WARNING: Caches not enabled\n");
 #endif

In fact, we can turn on I-cache safely by default, turn-off D-cache by default,
But give big warning to board-maintainer to fix it later if turn off D-cache.

This can keep the most of config file not change and keep using the
only one copy
of common d-cache enable function to avoid code duplication on every board.

Jason