Re: [PATCH v5 3/4] mtd: core: protect access to MTD devices while in suspend

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Sean Nyekjaer <sean@geanix.com>,
	linux-kernel@vger.kernel.org,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Boris Brezillon <bbrezillon@kernel.org>,
	linux-mtd@lists.infradead.org
Subject: Re: [PATCH v5 3/4] mtd: core: protect access to MTD devices while in suspend
Date: Fri, 3 Dec 2021 14:39:58 +0100	[thread overview]
Message-ID: <20211203143958.40645506@xps13> (raw)
In-Reply-To: <20211130143705.5d0404aa@collabora.com>

Hello,

> > Fine by me, lets drop this series.

FYI I've dropped the entire series from mtd/next. I'm waiting for the
fix discussed below (without abusing the chip mutex ;-) ).

Cheers,
Miquèl

> > We have +10.000 devices that runs with this patch:
> > 
> > diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> > index 1f0d542d5923..58d48c3070fa 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -4337,7 +4337,6 @@ static int nand_suspend(struct mtd_info *mtd)
> >  		ret = chip->ops.suspend(chip);
> >  	if (!ret)
> >  		chip->suspended = 1;
> > -	mutex_unlock(&chip->lock);
> >  
> >  	return ret;
> >  }
> > @@ -4350,7 +4349,6 @@ static void nand_resume(struct mtd_info *mtd)
> >  {
> >  	struct nand_chip *chip = mtd_to_nand(mtd);
> >  
> > -	mutex_lock(&chip->lock);
> >  	if (chip->suspended) {
> >  		if (chip->ops.resume)
> >  			chip->ops.resume(chip);
> >   
> 
> But it's abusing the chip lock... Use a wait queue as we did at the MTD
> level, and make nand_get_device() wait on this wait queue when the
> device is suspended.
> 
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