[U-Boot] [PATCH] mtest: Disable dcache during test

[Graeme Russ]

Hi Benoît,

On Tue, Sep 4, 2012 at 7:14 AM, Benoît Thébaudeau
<benoit.thebaudeau at advansee.com> wrote:
> Hi Albert,
>
> On Monday, September 3, 2012 6:50:14 PM, Albert ARIBAUD wrote:
>> Hi Benoît,
>>
>> On Mon, 3 Sep 2012 16:25:15 +0200 (CEST), Benoît Thébaudeau
>> <benoit.thebaudeau at advansee.com> wrote:
>>
>> > Dear Wolfgang Denk,
>> >
>> > On Sunday, September 2, 2012 6:30:23 PM, Wolfgang Denk wrote:
>> > > Dear Benoît Thébaudeau,
>> > >
>> > > In message
>> > > <1725235724.2300239.1344694624384.JavaMail.root at advansee.com> you
>> > > wrote:
>> > > >
>> > > > On 08/11/2012 05:18 AM, Mike Frysinger wrote:
>> > > ...
>> > > > > if you want dcache disabled, then why don't you run `dcache
>> > > > > off`
>> > > > > first ?  i
>> > > > > think it's useful to be able to do both, and forcing it one
>> > > > > way
>> > > > > is
>> > > > > wrong.
>> > > > >
>> > > > > thus, NAK from me.
>> > > > > -mike
>> > > >
>> > > > Because you will very likely trust mtest and forget about
>> > > > running
>> > > > `dcache off`
>> > > > first, so you may then be happy about falsely positive mtest
>> > > > results. Moreover,
>> > > > I can't find any sense or usefulness in running mtest with
>> > > > dcache
>> > > > enabled.
>> > >
>> > > I agree with Mike.
>> > >
>> > > "UNIX was not designed to stop you from doing stupid things,
>> > > because that would also stop you from doing clever things."
>> > >       -
>> > > Doug Gwyn
>> > >
>> > > So NAK from me, too.
>> >
>> > OK, but do you agree with the following that Mike and me agreed on
>> > after that?
>> > http://lists.denx.de/pipermail/u-boot/2012-August/130650.html
>> > http://lists.denx.de/pipermail/u-boot/2012-August/130726.html
>> > http://patchwork.ozlabs.org/patch/176909/
>>
>> I did already reply to this, but since the agreement is brought back,
>> I
>> think I should re-state my opinion: such a warning line will most
>> likely
>> be overlooked, thus has little value. People using mtest should know
>> that they must check/set dcache state before running mtest.
>
> If this line is overlooked, it's the same as not having it. If it is not
> overlooked, it is useful both to detail the test conditions and as a reminder
> not to do stupid things. This line does not prevent users from doing any manual
> dcache check/enable/disable operation they want before running mtest. All in
> all, adding this line can only be beneficial.

I agree - particularly when somebody else is looking at the output (on
the ML for example) and notices it.

I'm also inclined to not 100% trust dcache operations (we all know
that cache support is in a state of flux) so something like:

# dcache on
# mtest 0x80100000 0x90000000 0xaabb

If you get back:

Testing 0x80100000 ... 0x90000000 (dcache: off):

You know something is wrong with the dcache on implementation

Regards,

Graeme