From: Michal Nazarewicz <mina86@mina86.com>
To: Weijie Yang <weijie.yang.kh@gmail.com>,
Gregory Fong <gregory.0xf0@gmail.com>
Cc: linux-mm@kvack.org, Laura Abbott <lauraa@codeaurora.org>,
iamjoonsoo.kim@lge.com,
Marek Szyprowski <m.szyprowski@samsung.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Florian Fainelli <f.fainelli@gmail.com>,
Brian Norris <computersforpeace@gmail.com>
Subject: Re: CMA alignment question
Date: Wed, 05 Nov 2014 23:01:48 +0100 [thread overview]
Message-ID: <xa1tsihxwblf.fsf@mina86.com> (raw)
In-Reply-To: <CAL1ERfMYmQcQ_sX7E0HC2bXmC-imh4T-7Q4nBVQRXkQSaTjvQQ@mail.gmail.com>
> On Tue, Nov 04 2014, Gregory Fong wrote:
>> The alignment in cma_alloc() is done w.r.t. the bitmap. This is a
>> problem when, for example:
>>
>> - a device requires 16M (order 12) alignment
>> - the CMA region is not 16 M aligned
On Wed, Nov 05 2014, Weijie Yang wrote:
> I think the device driver should ensure that situation could not occur,
> by assign suitable alignment parameter in cma_declare_contiguous().
What about default CMA area? Besides, I think principle of least
surprise applies here and alignment should be physical.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +--<mpn@google.com>--<xmpp:mina86@jabber.org>--ooO--(_)--Ooo--
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WARNING: multiple messages have this Message-ID (diff)
From: Michal Nazarewicz <mina86@mina86.com>
To: Weijie Yang <weijie.yang.kh@gmail.com>,
Gregory Fong <gregory.0xf0@gmail.com>
Cc: linux-mm@kvack.org, Laura Abbott <lauraa@codeaurora.org>,
iamjoonsoo.kim@lge.com,
Marek Szyprowski <m.szyprowski@samsung.com>,
"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Florian Fainelli <f.fainelli@gmail.com>,
Brian Norris <computersforpeace@gmail.com>
Subject: Re: CMA alignment question
Date: Wed, 05 Nov 2014 23:01:48 +0100 [thread overview]
Message-ID: <xa1tsihxwblf.fsf@mina86.com> (raw)
In-Reply-To: <CAL1ERfMYmQcQ_sX7E0HC2bXmC-imh4T-7Q4nBVQRXkQSaTjvQQ@mail.gmail.com>
> On Tue, Nov 04 2014, Gregory Fong wrote:
>> The alignment in cma_alloc() is done w.r.t. the bitmap. This is a
>> problem when, for example:
>>
>> - a device requires 16M (order 12) alignment
>> - the CMA region is not 16 M aligned
On Wed, Nov 05 2014, Weijie Yang wrote:
> I think the device driver should ensure that situation could not occur,
> by assign suitable alignment parameter in cma_declare_contiguous().
What about default CMA area? Besides, I think principle of least
surprise applies here and alignment should be physical.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +--<mpn@google.com>--<xmpp:mina86@jabber.org>--ooO--(_)--Ooo--
next prev parent reply other threads:[~2014-11-05 22:01 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-04 21:03 CMA alignment question Gregory Fong
2014-11-04 21:03 ` Gregory Fong
2014-11-04 22:27 ` Michal Nazarewicz
2014-11-04 22:27 ` Michal Nazarewicz
2014-11-05 4:18 ` Gregory Fong
2014-11-05 4:18 ` Gregory Fong
2014-11-05 7:20 ` Weijie Yang
2014-11-05 7:20 ` Weijie Yang
2014-11-05 22:01 ` Michal Nazarewicz [this message]
2014-11-05 22:01 ` Michal Nazarewicz
2014-11-06 1:00 ` Weijie Yang
2014-11-06 1:00 ` Weijie Yang
2014-11-06 12:29 ` Michal Nazarewicz
2014-11-06 12:29 ` Michal Nazarewicz
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