From: Michael Ellerman <mpe@ellerman.id.au>
To: Will Deacon <will.deacon@arm.com>, "Koenig\,
Christian" <Christian.Koenig@amd.com>
Cc: "Carsten Haitzler" <Carsten.Haitzler@arm.com>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"David Airlie" <airlied@linux.ie>,
benh@kernel.crashing.org, "Michel Dänzer" <michel@daenzer.net>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
"Huang, Ray" <Ray.Huang@amd.com>,
"Zhang, Jerry" <Jerry.Zhang@amd.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
"Bernhard Rosenkränzer" <Bernhard.Rosenkranzer@linaro.org>
Subject: Re: [RFC PATCH] drm/ttm: force cached mappings for system RAM on ARM
Date: Tue, 15 Jan 2019 22:31:29 +1100 [thread overview]
Message-ID: <87a7k2yx66.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20190114193548.GB29600@fuggles.cambridge.arm.com>
Hi Will,
Will Deacon <will.deacon@arm.com> writes:
> [+ BenH and MPE]
>
> On Mon, Jan 14, 2019 at 07:21:08PM +0000, Koenig, Christian wrote:
>> Am 14.01.19 um 20:13 schrieb Will Deacon:
...
>
>> > The Arm architecture (and others including Power afaiu) doesn't
>> > guarantee coherency when memory is accessed using mismatched cacheability
>> > attributes.
...
>
>> As far as I know Power doesn't really supports un-cached memory at all,
>> except for a very very old and odd configuration with AGP.
>
> Hopefully Michael/Ben can elaborate here, but I was under the (possibly
> mistaken) impression that mismatched attributes could cause a machine-check
> on Power.
That's what I've always been told, but I can't actually find where it's
documented, I'll keep searching.
But you're right that mixing cached / uncached is not really supported,
and probably results in a machine check or worse.
cheers
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next prev parent reply other threads:[~2019-01-15 11:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-10 7:28 [RFC PATCH] drm/ttm: force cached mappings for system RAM on ARM Ard Biesheuvel
2019-01-10 8:36 ` Zhang, Jerry(Junwei)
2019-01-10 8:36 ` Koenig, Christian
2019-01-10 9:34 ` Michel Dänzer
2019-01-14 10:53 ` Ard Biesheuvel
2019-01-14 11:38 ` Koenig, Christian
2019-01-14 17:32 ` Ard Biesheuvel
[not found] ` <9f956898-7973-98ee-6bf1-e1d445e9d365@amd.com>
2019-01-14 19:13 ` Will Deacon
2019-01-14 19:21 ` Koenig, Christian
2019-01-14 19:35 ` Will Deacon
2019-01-15 11:31 ` Michael Ellerman [this message]
2019-01-16 0:33 ` Benjamin Herrenschmidt
2019-01-16 7:35 ` Koenig, Christian
2019-01-16 7:47 ` Ard Biesheuvel
2019-01-17 6:07 ` Benjamin Herrenschmidt
2019-01-17 8:02 ` Ard Biesheuvel
2019-01-17 5:59 ` Benjamin Herrenschmidt
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