[U-Boot] [PATCH] mmc:dcache: Cache line size aligned internal MMC buffers

Anton Staaf
2011-08-24T20:13:47Z

On Wed, Aug 24, 2011 at 12:18 PM, Lukasz Majewski <majess1982@gmail.com> wrote:
> On Wed, 24 Aug 2011 11:25:42 -0700
> Anton Staaf <robotboy@google.com> wrote:
>
>> On Wed, Aug 24, 2011 at 11:12 AM, Wolfgang Denk <wd@denx.de> wrote:
>> > Dear Anton Staaf,
>> >
>> > In message
>> > <CAF6FioWBsjFa+QdFNHEQGO50eLoqZMc--Yt3-iYX6DWr=hcOrg@mail.gmail.com>
>> > you wrote:
>> >>
>> >> >> 4. get_dcache_line_size() can be simply defined as
>> >> >> #define get_dcache_line_size() CONFIG_SYS_CACHE_LINE_SIZE if we
>> >> >> _really_ want to save a few bytes.
>> >> >
>> >> > Actually I fail to understand why we would ever need
>> >> > get_dcache_line_size() in a boot loader.
>> >>
>> >> It is required so that we can correctly allocate buffers that will
>> >> be used by DMA engines to read or write data. ?The reason that
>> >> these
>> >
>> > No, it is definitely NOT needed for this purpose - we have been
>> > using CONFIG_SYS_CACHE_LINE_SIZE for more than a decade without
>> > problems, so I don't really understand why we now would need a new
>> > function for this?
>>
>
> Ok, so one problem solved :-).
>
>> Ahh, I misunderstood your question. ?I thought you were asking about
>> the need to know the cache line size. ?Not it's specific
>> implementation as a function call. ?In which case, I agree, and am
>> happy to use CONFIG_SYS_CACHE_LINE_SIZE, though I don't see any
>> definitions of CONFIG_SYS_CACHE_LINE_SIZE in the entire U-Boot tree.
>> What have I missed?
>>
>
> There are some similar definitions:
> ./include/configs/atstk1006.h:#define CONFIG_SYS_DCACHE_LINESZ 32
> ./include/configs/atngw100.h:#define CONFIG_SYS_DCACHE_LINESZ 32
> ./include/configs/favr-32-ezkit.h:#define
> CONFIG_SYS_DCACHE_LINESZ 32

I would assume that these should be changed to the one mentioned by
Wolfgang. But this still leaves us with a question of how to make a
simple, easy to use macro for allocating cache line size aligned stack
buffers. I'll work on that some more and see if I can come up with
something.

Thanks,
Anton

>
>> Thanks,
>> ? ? Anton
>>
>> >
>> > Best regards,
>> >
>> > Wolfgang Denk
>> >
>> > --
>> > DENX Software Engineering GmbH, ? ? MD: Wolfgang Denk & Detlev
>> > Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194
>> > Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax:
>> > (+49)-8142-66989-80 Email: wd at denx.de Brain: an apparatus with
>> > which we think we think. ? ?- Ambrose Bierce
>> >
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>
> Regards,
> Lukasz Majewski
>