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

[Anton Staaf]

On Wed, Aug 24, 2011 at 12:18 PM, Lukasz Majewski <majess1982 at gmail.com> wrote:
> On Wed, 24 Aug 2011 11:25:42 -0700
> Anton Staaf <robotboy at google.com> wrote:
>
>> On Wed, Aug 24, 2011 at 11:12 AM, Wolfgang Denk <wd at denx.de> wrote:
>> > Dear Anton Staaf,
>> >
>> > In message
>> > <CAF6FioWBsjFa+QdFNHEQGO50eLoqZMc--Yt3-iYX6DWr=hcOrg at 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
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>> > which we think we think.    - Ambrose Bierce
>> >
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>
> Regards,
> Lukasz Majewski
>