From: Scott Wood <scottwood@freescale.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Wood Scott-B07421 <B07421@freescale.com>,
Xie Shaohui-B21989 <B21989@freescale.com>,
Hu Mingkai-B21284 <B21284@freescale.com>,
Chen Yuanquan-B41889 <B41889@freescale.com>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
Timur Tabi <timur@freescale.com>
Subject: Re: [PATCH] powerpc/mm: add ZONE_NORMAL zone for 64 bit kernel
Date: Mon, 23 Jul 2012 20:37:11 -0500 [thread overview]
Message-ID: <500DFC47.3090509@freescale.com> (raw)
In-Reply-To: <1343086215.2957.47.camel@pasglop>
On 07/23/2012 06:30 PM, Benjamin Herrenschmidt wrote:
> On Tue, 2012-07-24 at 09:29 +1000, Benjamin Herrenschmidt wrote:
>
>> The layers in between, not the well behaved drivers. Again, we have
>> ZONE_DMA32 specifically for the purpose, why use something else ?
>>
>> In any case, make the whole thing at the very least a config option, I
>> don't want sane HW to have to deal with split zones.
>
> Or if possible a flag set by machine probe()
I suggested making the threshold configurable by platform code. Sane
hardware would leave it at its default of infinity (~0ULL), and you
wouldn't have a split zone. Our hardware would set it at 31-bit.
It looks like this is already sort-of done for ISA_DMA_THRESHOLD for
32-bit non-coherent-DMA platforms (amigaone sets a 24-bit threshold),
though I don't see where ZONE_DMA is limited accordingly.
We'd add an additional threshold for ZONE_DMA32, make it actually affect
the zone definition, and make the standard alloc_coherent() honor it.
-Scott
next prev parent reply other threads:[~2012-07-24 1:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-20 12:21 [PATCH] powerpc/mm: add ZONE_NORMAL zone for 64 bit kernel Shaohui Xie
2012-07-23 6:06 ` Benjamin Herrenschmidt
2012-07-23 16:17 ` Scott Wood
2012-07-23 22:20 ` Benjamin Herrenschmidt
2012-07-23 23:08 ` Tabi Timur-B04825
2012-07-23 23:12 ` Benjamin Herrenschmidt
2012-07-23 23:15 ` Timur Tabi
2012-07-23 23:29 ` Benjamin Herrenschmidt
2012-07-23 23:30 ` Benjamin Herrenschmidt
2012-07-24 1:37 ` Scott Wood [this message]
2012-07-23 23:36 ` Timur Tabi
2012-07-24 3:08 ` Benjamin Herrenschmidt
2012-07-24 3:52 ` Tabi Timur-B04825
2012-07-24 3:59 ` Zang Roy-R61911
2012-07-24 4:04 ` Tabi Timur-B04825
2012-07-24 4:45 ` Benjamin Herrenschmidt
2012-07-24 8:01 ` Bhushan Bharat-R65777
2012-07-24 1:49 ` Scott Wood
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