RE: [LINUX PATCH v18 1/2] mtd: rawnand: nand_micron: Do not over write driver's read_page()/write_page()

[Naga Sureshkumar Relli <nagasure@xxxxxxxxxx>]

> -----Original Message-----
> From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> Sent: Wednesday, July 17, 2019 1:25 PM
> To: Naga Sureshkumar Relli <nagasure@xxxxxxxxxx>
> Cc: miquel.raynal@xxxxxxxxxxx; bbrezillon@xxxxxxxxxx; richard@xxxxxx;
> dwmw2@xxxxxxxxxxxxx; computersforpeace@xxxxxxxxx; marek.vasut@xxxxxxxxx;
> vigneshr@xxxxxx; yamada.masahiro@xxxxxxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Michal Simek <michals@xxxxxxxxxx>; Srikanth Vemula
> <svemula@xxxxxxxxxx>; nagasuresh12@xxxxxxxxx
> Subject: Re: [LINUX PATCH v18 1/2] mtd: rawnand: nand_micron: Do not over write
> driver's read_page()/write_page()
> 
> On Wed, 17 Jul 2019 05:33:35 +0000
> Naga Sureshkumar Relli <nagasure@xxxxxxxxxx> wrote:
> 
> > Hi Boris,
> >
> > > -----Original Message-----
> > > From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> > > Sent: Tuesday, July 16, 2019 1:15 PM
> > > To: Naga Sureshkumar Relli <nagasure@xxxxxxxxxx>
> > > Cc: miquel.raynal@xxxxxxxxxxx; bbrezillon@xxxxxxxxxx;
> > > richard@xxxxxx; dwmw2@xxxxxxxxxxxxx; computersforpeace@xxxxxxxxx;
> > > marek.vasut@xxxxxxxxx; vigneshr@xxxxxx;
> > > yamada.masahiro@xxxxxxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; linux-
> > > kernel@xxxxxxxxxxxxxxx; Michal Simek <michals@xxxxxxxxxx>; Srikanth
> > > Vemula <svemula@xxxxxxxxxx>; nagasuresh12@xxxxxxxxx
> > > Subject: Re: [LINUX PATCH v18 1/2] mtd: rawnand: nand_micron: Do not
> > > over write driver's read_page()/write_page()
> > >
> > > On Tue, 16 Jul 2019 09:31:37 +0200
> > > Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> wrote:
> > >
> > > > On Mon, 15 Jul 2019 23:30:51 -0600 Naga Sureshkumar Relli
> > > > <naga.sureshkumar.relli@xxxxxxxxxx> wrote:
> > > >
> > > > > Add check before assigning chip->ecc.read_page() and
> > > > > chip->ecc.write_page()
> > > > >
> > > > > Signed-off-by: Naga Sureshkumar Relli
> > > > > <naga.sureshkumar.relli@xxxxxxxxxx>
> > > > > ---
> > > > > Changes in v18
> > > > >  - None
> > > > > ---
> > > > >  drivers/mtd/nand/raw/nand_micron.c | 7 +++++--
> > > > >  1 file changed, 5 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/mtd/nand/raw/nand_micron.c
> > > > > b/drivers/mtd/nand/raw/nand_micron.c
> > > > > index cbd4f09ac178..565f2696c747 100644
> > > > > --- a/drivers/mtd/nand/raw/nand_micron.c
> > > > > +++ b/drivers/mtd/nand/raw/nand_micron.c
> > > > > @@ -500,8 +500,11 @@ static int micron_nand_init(struct nand_chip *chip)
> > > > >  		chip->ecc.size = 512;
> > > > >  		chip->ecc.strength = chip->base.eccreq.strength;
> > > > >  		chip->ecc.algo = NAND_ECC_BCH;
> > > > > -		chip->ecc.read_page = micron_nand_read_page_on_die_ecc;
> > > > > -		chip->ecc.write_page = micron_nand_write_page_on_die_ecc;
> > > > > +		if (!chip->ecc.read_page)
> > > > > +			chip->ecc.read_page = micron_nand_read_page_on_die_ecc;
> > > > > +
> > > > > +		if (!chip->ecc.write_page)
> > > > > +			chip->ecc.write_page = micron_nand_write_page_on_die_ecc;
> > > > >
> > > >
> > > > Seriously?! I told you this was inappropriate and you keep sending
> > > > this patch. So let's make it clear:
> > > >
> > > > Nacked-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> > > >
> > > > Fix your controller driver instead of adding hacks to the Micron logic!
> > >
> > > Not even going to review the other patch: if you have to do that,
> > > that means the driver is broken. On a side note, this patch series
> > > is still not threaded as it should be and it's a v18 for a damn NAND
> > > controller driver! Sorry but you reached the limit of my patience. Please find someone to
> help you with that task.
> > My intention is not to resend this 1/2 again. Sorry for that.
> > We already had some discussion on [v17 1/2],
> > https://lkml.org/lkml/2019/6/26/430
> > And there we didn't conclude that raw_read()/writes().
> 
> Yes, looks like I never replied to that one, but I think my previous explanation were clear
> enough to not argue on that aspect any longer/
You replied on that. But I thought that you have some more inputs to give.
Ok understood thanks.
> 
> > So I thought that, will send updated driver along with this patch,
> > then will get more information about The issue on the latest driver review.
> 
> More on that topic. I don't think you ever tested on-die ECC on a Micron NAND, otherwise
> you would have noticed that your solution completely bypasses the on-die ECC logic (and this
> will clearly break existing on-die ECC users). See, that's what I'm complaining about, Looks
> like you don't really understand what you're doing.
We tested it with pl353_read/write_page_raw(). Hence no information of bit flips.
As I said, will fix the driver to use micron _read_page_ondie().
> 
> > There is nothing like keep on sending this patch, As you people are
> > experts in the driver review, if this patch is a hack, then we will definitely fix that in
> controller driver. I will find a way to do that.
> >
> > But in this flow of patch sending, if the work I did hurts you, then I am really sorry for that.
> 
> I'm not offended, just tired going through the same driver over and over again, reporting
> things that are wrong/inappropriate to then realize you only addressed of a tiny portion of it in
> the following version. My last reviews were rather incomplete because of that, and now I'm
> giving up.
> 
> > Will fix this issue in the controller driver and will send the updated one.
> 
> How? You say you'll fix the issue but I'm not even sure you understand what the issue is?
> Clearly, the patch you've posted doesn't fix anything, it's just papering over the fact that your
> controller driver is not supporting raw accesses (or at least, not supporting it properly).
> 
> Have you even looked at the datasheet you pointed to in patch 2 [1]?
> Just went through it, and found a field that's supposed to control the ECC engine activation:
> ecc_memcfg.ecc_mode. I don't see anything changing that field in your code, so I guess raw
> accesses are actually not really happening with the ECC engine disabled...
It is happening, in the drivers ecc_init(), if the ecc mode is ON_DIE, then 
We are calling pl353_smc_set_ecc_mode(PL353_SMC_ECCMODE_BYPASS).
This will internally disables the HW-ECC.
> 
> > Could you please let me know if this is OK.
> 
> You can send a new version, I'm just saying I won't spend time reviewing it.
> 
> >
> > I will send the series as threaded one from next time onwards.
> >
> > Thanks,
> > pcieNaga Sureshkumar Relli
> 
> [1]http://infocenter.arm.com/help/topic/com.arm.doc.ddi0380g/DDI0380G_smc_pl350_seri
> es_r2p1_trm.pdf

Regards,
Naga Sureshkumar Relli

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