> On 04 Apr 2017, at 22:09, Marek Vasut <ma...@denx.de> wrote:
>
>> The DWC3 flush expands to a clean+invalidate. It is not wrong, as long as
>> it is used as in my patch:
>> a. before the first time data is expected to be written by the peripheral
>> (i.e.
>> before the peripheral is started)—to ensure that the cache line is not cached
>> any longer…
>
> So invalidate() is enough ?
If I had to write this from scratch, I’d got with the paranoid sequence of:
handler():
{
invalidate
do my stuff
clean
}
However, some architectures in U-Boot (e.g. ARMv8) don’t implement the
invalidate verb. Given this, I’d rather stay as close to what’s already there.
Note that using flush (i.e. clean+invalidate) aligns with how caches are
managed throughout various other drivers in U-Boot.
>
>> b. after the driver modifies any buffers (i.e. anything modified will be
>> written
>> back) and before it next reads the buffers expecting possibly changed data
>> (i.e. invalidating).
>
> So flush+invalidate ? Keep in mind this driver may not be used on
> ARMv7/v8 only …
Yes, a clean+invalidate.
The flush_dcache_range(…, …) function in U-Boot implements C+I semantics
at least on arm, arm64, avr32, powerpc, xtensa …
Regards,
Philipp.
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