linux-kernel - Re: [PATCH] mtd: rawnand: marvell: pass ms delay to wait

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Date:   Thu, 3 May 2018 09:05:07 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Cc:     "boris.brezillon@...tlin.com" <boris.brezillon@...tlin.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: rawnand: marvell: pass ms delay to wait_op

Hi Chris,

On Thu, 3 May 2018 05:28:32 +0000, Chris Packham
<Chris.Packham@...iedtelesis.co.nz> wrote:

> On 03/05/18 14:21, Chris Packham wrote:
> > marvell_nfc_wait_op() expects the delay to be expressed in milliseconds
> > but nand_sdr_timings uses picoseconds. Use PSEC_TO_MSEC when passing
> > tPROG_max to marvell_nfc_wait_op().
> > 
> > Fixes: 02f26ecf8c772 ("mtd: nand: add reworked Marvell NAND controller driver")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
> > ---
> >   drivers/mtd/nand/raw/marvell_nand.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/raw/marvell_nand.c b/drivers/mtd/nand/raw/marvell_nand.c
> > index 1d779a35ac8e..e4b964fd40d8 100644
> > --- a/drivers/mtd/nand/raw/marvell_nand.c
> > +++ b/drivers/mtd/nand/raw/marvell_nand.c
> > @@ -1074,7 +1074,7 @@ static int marvell_nfc_hw_ecc_hmg_do_write_page(struct nand_chip *chip,
> >   		return ret;
> >   
> >   	ret = marvell_nfc_wait_op(chip,
> > -				  chip->data_interface.timings.sdr.tPROG_max);
> > +				  PSEC_TO_MSEC(chip->data_interface.timings.sdr.tPROG_max));
> >   	return ret;
> >   }
> >   
> > @@ -1494,7 +1494,7 @@ static int marvell_nfc_hw_ecc_bch_write_page(struct mtd_info *mtd,
> >   	}
> >   
> >   	ret = marvell_nfc_wait_op(chip,
> > -				  chip->data_interface.timings.sdr.tPROG_max);
> > +				  PSEC_TO_MSEC(chip->data_interface.timings.sdr.tPROG_max));
> >   
> >   	marvell_nfc_disable_hw_ecc(chip);
> >     
> 
> Actually I'm not so sure about this patch. While passing the pico-second 
> value for tPROG_max is clearly wrong and leads to seemingly indefinite 
> hangs on some systems. Converting the times to micro-seconds leaves us 
> with delays that are far too short.

It is not micro but milli-seconds here.

> 
> The old pxa3xx driver had hard coded 200ms delays. These delays now work 
> out to 1ms which seems every bit as wrong as 600000000ms.

200ms is extremely long, I guess typical values are ~200-500us, so this
1ms timeout does not scare me :)

I'll let Boris conclude.

Reviewed-by: Miquel Raynal <miquel.raynal@...tlin.com>

Thanks.

-- 
Miquel Raynal, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com