linux-kernel - RE: [PATCH] mtd: nand: gpmi: add proper raw access support

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Date:	Thu, 2 Oct 2014 16:52:29 +1000
From:	Iwo Mergler <Iwo.Mergler@...commwireless.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
CC:	Huang Shijie <shijie8@...il.com>,
	Mike Voytovich <mvoytovich@...pal.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Huang Shijie <b32955@...escale.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	Roy Lee <roylee@...pal.com>,
	Brian Norris <computersforpeace@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH] mtd: nand: gpmi: add proper raw access support

On Tue, 30 Sep 2014 18:04:15 +1000
Boris Brezillon <boris.brezillon@...e-electrons.com> wrote:

> Hi Iwo,
> 
> On Mon, 29 Sep 2014 11:22:11 +1000
> Iwo Mergler <Iwo.Mergler@...commwireless.com> wrote:
> 
> > On Thu, 11 Sep 2014 22:36:16 +1000
> > Boris BREZILLON <boris.brezillon@...e-electrons.com> wrote:
> > > 
> > > Well, I don't know about freescale specific tools, but at least I
> > > have an example with mtd_nandbiterrs module.
> > > This module is assuming it can write only the data part of a NAND
> > > page without modifying the OOB area (see [1]), which in GPMI
> > > controller case is impossible because raw write function store
> > > the data as if there were no specific scheme, while there is one:
> > > (metadata + n x (data_chunk + ECC bytes) + remaining_bytes).
> > > 
> > 
> > Hi Boris,
> > 
> > 
> > just as an aside, only the incremental bit errors test in
> > nandbiterrs positively requires raw data write.
> > 
> > The overwrite test (re-write the same page data repeatedly without
> > erase), only uses raw access because I was lazy. A normal ECC write
> > would do just as well.
> 
> Okay.
> Anyway, the test I'm really interested in is the incremental bit
> errors test :-).
> 
> BTW, any reason you chose to implement this test/testsuite as a
> module ?
> From my understanding (and tell me if I'm wrong) we could do the same
> from user-space.
> 
> Best Regards,
> 
> Boris
> 

Hi Boris,


can't say I have good excuses, but here goes. :-)

I was writing a NAND driver, so my brain was in kernel mode. It made it
slightly easier to trace the operations from end-to-end.

It's also possible that I didn't have an userspace at the time and had the
test compiled in, my memory is a little fuzzy...

Otherwise, yes, you could probably do it from userspace. I'm not sure
if there is a way to determine the number of corrected bit errors for
a specific page read. ECCGETSTATS seems to be global.


Best regards,

Iwo

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