From: Segher Boessenkool <segher@kernel•crashing.org>
To: Vladislav Buzov <vbuzov@ru•mvista.com>
Cc: linuxppc-dev list <linuxppc-dev@ozlabs•org>
Subject: Re: [RFC/PATCH] powerpc: MPC7450 L2 HW cache flush feature utilization
Date: Fri, 15 Jun 2007 10:14:24 +0200 [thread overview]
Message-ID: <6c416bf9f79a648fc82f64619aca86de@kernel.crashing.org> (raw)
In-Reply-To: <467176EB.7060404@ru.mvista.com>
>> Are these errata 7448-only? If not, I wonder what is
>> done on PowerMacs?
>
> This is a errata for 7448 only. I've looked through errata for other=20=
> 7450 processors (7450, 7457) and they contain the same erratum for L2=20=
> cache: "L2 hardware flush may not flush every line from the L2 cache"=20=
> The workaround for this problem is: "Set the IONLY and DONLY bits in=20=
> the L2CR prior to the L2 hardware flush", and the projected solution=20=
> is: "The workaround has been documented in the MPC7450 RISC=20
> Microprocessor Family User=92s Manual as the correct way to flush the =
L2=20
> cache"
Okay, so it is for all members of the 7450 family. Good :-)
>> Looks reasonable enough to me... if it works (on all
>> things considered "7450" by the kernel).
>
> I've double checked this. All processors considered 7450 in the kernel=20=
> are covered by MPC7450 RISC Microprocessor Family Reference Manual=20
> where hardware cache flushing procedure is described.
Nice. Now all that remains to be done is for the patch to
be tested on actual hardware for at least a few of those
other CPUs. Any volunteers?
>>> /* TODO: use HW flush assist when available */
>>
>> You want to get rid of this old comment though -- and
>> perhaps branch over the non-hardware-assisted cache
>> flushing code.
>
> Ok, I agree that the comment is obsolete now. Would you please explain=20=
> why the branch over non-hardware-assisted code should be removed as=20
> well. Technically the cache is flushed and there is no need to use=20
> extra commands to fill and then re-flush the cache.
I said such a branch should be added, not removed -- it
appears from your reply that you are skipping it already
and I just missed it?
Segher
next prev parent reply other threads:[~2007-06-15 8:14 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-13 10:19 [RFC/PATCH] powerpc: MPC7450 L2 HW cache flush feature utilization Vladislav Buzov
2007-06-14 13:56 ` Segher Boessenkool
2007-06-14 17:12 ` Vladislav Buzov
2007-06-14 22:26 ` Mark A. Greer
2007-06-15 8:16 ` Segher Boessenkool
2007-06-15 8:55 ` Vladislav D. Buzov
2007-06-15 9:01 ` Segher Boessenkool
2007-06-15 9:33 ` Vladislav D. Buzov
2007-06-15 10:44 ` Segher Boessenkool
2007-06-15 8:14 ` Segher Boessenkool [this message]
2007-06-15 8:42 ` Vladislav D. Buzov
2007-06-15 8:56 ` Segher Boessenkool
2007-06-15 21:20 ` Mark A. Greer
2007-06-15 22:14 ` Segher Boessenkool
2007-06-21 12:37 ` Benjamin Herrenschmidt
2007-06-22 15:22 ` Vladislav Buzov
2007-06-23 15:46 ` Segher Boessenkool
2007-06-25 14:09 ` Vladislav Buzov
2007-06-28 8:24 ` Segher Boessenkool
2007-06-28 9:13 ` Benjamin Herrenschmidt
2007-06-28 10:47 ` Vladislav Buzov
2007-06-28 11:09 ` Benjamin Herrenschmidt
2007-06-25 19:00 ` Vladislav Buzov
2007-06-28 8:35 ` Segher Boessenkool
2007-06-29 10:41 ` Vladislav Buzov
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