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

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Date:	Thu, 24 Nov 2011 13:07:13 +0200
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	LiuShuo <b35362@...escale.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

On Thu, 2011-11-24 at 18:02 +0800, LiuShuo wrote:
> 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 ?

Up to you, I do not have suggestions, just expressed a concern. I'd keep
the buffer smaller if possible. By the time 16KiB pages appear, your HW
may retire already :-)

-- 
Best Regards,
Artem Bityutskiy

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