linux-kernel - Re: [PATCH 3/3] mtd/nand : workaround for Freescale FCM to support large-page Nand chip

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Message-ID: <4ECE162D.7080408@freescale.com>
Date:	Thu, 24 Nov 2011 18:02:21 +0800
From:	LiuShuo <b35362@...escale.com>
To:	<dedekind1@...il.com>
CC:	Li Yang-R58472 <r58472@...escale.com>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"Artem.Bityutskiy@...ia.com" <Artem.Bityutskiy@...ia.com>,
	Wood Scott-B07421 <B07421@...escale.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] mtd/nand : workaround for Freescale FCM to support
 large-page Nand chip

于 2011年11月24日 16:16, Artem Bityutskiy 写道:
> On Thu, 2011-11-24 at 07:49 +0000, Li Yang-R58472 wrote:
>>> Subject: Re: [PATCH 3/3] mtd/nand : workaround for Freescale FCM to support
>>> large-page Nand chip
>>>
>>> On Thu, 2011-11-24 at 08:41 +0800, b35362@...escale.com wrote:
>>>> +               /*
>>>> +                * Freescale FCM controller has a 2K size limitation of buffer
>>>> +                * RAM, so elbc_fcm_ctrl->buffer have to be used if writesize
>>>> +                * of chip is greater than 2048.
>>>> +                * We malloc a large enough buffer (maximum page size is
>>> 16K).
>>>> +                */
>>>> +               elbc_fcm_ctrl->buffer = kmalloc(1024 * 16 + 1024,
>>> GFP_KERNEL);
>>>
>>> Are there NANDs with 16KiB page size?
>> We are not sure, but are there possibility that chip with 16K page will appear?  Or maybe we can add a MACRO for the maximum page size?
> I do not know, but I know that allocating 32KiB of contiguous physical
> RAM may cause unneeded memory pressure and even fail if the memory is
> too fragmented. So I would not go for this unless this is necessary.
What is your suggestion ? 8k is enough ?
> Did you try to look how the NAND base interface could be changed to
> avoid re-allocation altogether, BTW?
This buffer is a controller-wide resource( as Scott said), I only 
allocate buffer one time in this version.
It should be a large enough buffer for all chips.

-Liu Shuo

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