From: Scott Wood <scottwood@freescale.com> To: <dedekind1@gmail.com> Cc: dwmw2@infradead.org, b35362@freescale.com, linux-mtd@lists.infradead.org, linuxppc-dev@ozlabs.org Subject: Re: [PATCH v2] mtd/nand : workaround for Freescale FCM to support large-page Nand chip Date: Mon, 15 Aug 2011 11:11:12 -0500 [thread overview] Message-ID: <4E494520.7050509@freescale.com> (raw) In-Reply-To: <1313423954.8691.17.camel@sauron> On 08/15/2011 10:59 AM, Artem Bityutskiy wrote: > On Tue, 2011-07-12 at 12:48 +0800, b35362@freescale.com wrote: >> + /* >> + * Hack for supporting the flash chip whose writesize is >> + * larger than 2K bytes. >> + */ >> + if (mtd->writesize > 2048) { >> + elbc_fcm_ctrl->subpage_shift = ffs(mtd->writesize >> 11) - 1; >> + elbc_fcm_ctrl->subpage_mask = >> + (1 << elbc_fcm_ctrl->subpage_shift) - 1; >> + /* >> + * Rewrite mtd->writesize, mtd->oobsize, chip->page_shift >> + * and chip->pagemask. >> + */ >> + mtd->writesize = 2048; >> + mtd->oobsize = 64; >> + chip->page_shift = ffs(mtd->writesize) - 1; >> + chip->pagemask = (chip->chipsize >> chip->page_shift) - 1; >> + } > > So basically if the flash has 4KiB NAND pages, you are considering it as > a flash with 2KiB NAND pages. But surely this will work only if the > underlying flash has NOP 2 at least. Or even, if you consider that JFFS2 > and YAFFS want to write to OOB, you need NOP 4 (2 ECC writes and 2 > writes from YAFFS/JFFS2) ? So this won't work for NOP1 flashes? Right. The set of chips that work with this controller is still larger with this than without this. It looks like NOP1 tends to be MLC -- you probably wouldn't want to use MLC with this controller anyway as it only does 1-bit ECC. > Isn't it an ugly hack? Less ugly than some other approaches that were considered. :-) But yes, it's a hack (even says so in the comment). The other option is "it doesn't work". -Scott
WARNING: multiple messages have this Message-ID (diff)
From: Scott Wood <scottwood@freescale.com> To: <dedekind1@gmail.com> Cc: dwmw2@infradead.org, Li Yang <leoli@freescale.com>, b35362@freescale.com, linux-mtd@lists.infradead.org, linuxppc-dev@ozlabs.org Subject: Re: [PATCH v2] mtd/nand : workaround for Freescale FCM to support large-page Nand chip Date: Mon, 15 Aug 2011 11:11:12 -0500 [thread overview] Message-ID: <4E494520.7050509@freescale.com> (raw) In-Reply-To: <1313423954.8691.17.camel@sauron> On 08/15/2011 10:59 AM, Artem Bityutskiy wrote: > On Tue, 2011-07-12 at 12:48 +0800, b35362@freescale.com wrote: >> + /* >> + * Hack for supporting the flash chip whose writesize is >> + * larger than 2K bytes. >> + */ >> + if (mtd->writesize > 2048) { >> + elbc_fcm_ctrl->subpage_shift = ffs(mtd->writesize >> 11) - 1; >> + elbc_fcm_ctrl->subpage_mask = >> + (1 << elbc_fcm_ctrl->subpage_shift) - 1; >> + /* >> + * Rewrite mtd->writesize, mtd->oobsize, chip->page_shift >> + * and chip->pagemask. >> + */ >> + mtd->writesize = 2048; >> + mtd->oobsize = 64; >> + chip->page_shift = ffs(mtd->writesize) - 1; >> + chip->pagemask = (chip->chipsize >> chip->page_shift) - 1; >> + } > > So basically if the flash has 4KiB NAND pages, you are considering it as > a flash with 2KiB NAND pages. But surely this will work only if the > underlying flash has NOP 2 at least. Or even, if you consider that JFFS2 > and YAFFS want to write to OOB, you need NOP 4 (2 ECC writes and 2 > writes from YAFFS/JFFS2) ? So this won't work for NOP1 flashes? Right. The set of chips that work with this controller is still larger with this than without this. It looks like NOP1 tends to be MLC -- you probably wouldn't want to use MLC with this controller anyway as it only does 1-bit ECC. > Isn't it an ugly hack? Less ugly than some other approaches that were considered. :-) But yes, it's a hack (even says so in the comment). The other option is "it doesn't work". -Scott
next prev parent reply other threads:[~2011-08-15 16:11 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-07-12 4:48 [PATCH v2] mtd/nand : workaround for Freescale FCM to support large-page Nand chip b35362 2011-07-12 4:48 ` b35362 2011-08-03 6:15 ` Li Yang-R58472 2011-08-03 6:15 ` Li Yang-R58472 2011-08-15 15:59 ` Artem Bityutskiy 2011-08-15 15:59 ` Artem Bityutskiy 2011-08-15 16:11 ` Scott Wood [this message] 2011-08-15 16:11 ` Scott Wood 2011-08-15 16:24 ` Artem Bityutskiy 2011-08-15 16:24 ` Artem Bityutskiy 2011-09-02 7:10 ` Stijn Devriendt 2011-09-02 7:10 ` Stijn Devriendt
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