linux-kernel - Re: [PATCH 2/2] dma: mv_xor: Use high

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 29 Oct 2013 12:15:18 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	sachin.kamat@...aro.org, Vinod Koul <vinod.koul@...el.com>,
	dmaengine@...r.kernel.org
Subject: Re: [PATCH 2/2] dma: mv_xor: Use high_base mmio where appropriate

On Tue, Oct 29, 2013 at 2:32 AM, Thomas Petazzoni
<thomas.petazzoni@...e-electrons.com> wrote:
> Dan, Ezequiel,
>
> On Tue, 29 Oct 2013 05:34:08 -0300, Ezequiel Garcia wrote:
>
>> > On Mon, Oct 28, 2013 at 3:54 PM, Ezequiel Garcia
>> > <ezequiel.garcia@...e-electrons.com> wrote:
>> > > Despite requesting two memory resources, called 'base' and 'high_base', the
>> > > driver uses explicitly only the former. The latter is being used implicitly
>> > > by addressing at offset +0x200, which in practice accesses high_base.
>> > >
>> > > Instead of relying in such trick, let's define the registers with the
>> > > offset from high_base, and use high_base explicitly where appropriate.
>> > >
>> > > Signed-off-by: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
>> > > ---
>> > >  drivers/dma/mv_xor.c |  3 ++-
>> > >  drivers/dma/mv_xor.h | 25 +++++++++++++------------
>> > >  2 files changed, 15 insertions(+), 13 deletions(-)
>> >
>> > Since it's unused I'd prefer a patch that just deletes xor_high_base.
>> >
>>
>> It's wrongly *unused*, the mmio high_base is actually being used
>> implicitly by always addressing at an offset that addresses +200.
>>
>> Deleting high_base would actually make it worse, for that region
>> will no longer be ioremaped. Maybe the commit message is not clear
>> about it?
>
> I agree with Ezequiel, and I believe his patch is appropriate. The
> registers for the XOR engines are indeed split in two areas, so it
> makes sense to have this xor_base / xor_high_base split that reflects
> the register mapping passed from the Device Tree, and use this split in
> the macros used to access the registers.
>

Ah ok, so it's a bug if an implementation ever puts the second
resource window at a non 0x200 offset.

Ezequiel , can you resend the patch to the new
dmaengine@...r.kernel.org list (patchwork queue) and clarify that this
is a fix rather than a pure cleanup in the changelog?  At least
cleanup is how I first read it.

Thanks for the clarification.

--
Dan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/