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Date: Mon, 13 Dec 2021 10:28:01 +0100
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Sean Nyekjaer <sean@...nix.com>, linux-kernel@...r.kernel.org,
Marek Szyprowski <m.szyprowski@...sung.com>,
Richard Weinberger <richard@....at>,
Vignesh Raghavendra <vigneshr@...com>,
Boris Brezillon <bbrezillon@...nel.org>,
linux-mtd@...ts.infradead.org
Subject: Re: [PATCH v5 3/4] mtd: core: protect access to MTD devices while
in suspend
On Mon, 13 Dec 2021 10:10:25 +0100
Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> Hi Sean,
>
> sean@...nix.com wrote on Fri, 10 Dec 2021 14:25:35 +0100:
>
> > On Thu, Dec 09, 2021 at 03:28:11PM +0100, Miquel Raynal wrote:
> > > Hi Sean,
> > >
> > > sean@...nix.com wrote on Thu, 9 Dec 2021 15:07:21 +0100:
> > >
> > > > On Fri, Dec 03, 2021 at 02:39:58PM +0100, Miquel Raynal wrote:
> > > > > 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 ;-) ).
> > > >
> > > > Cool, looking forward to test a patch series :)
> > >
> > > Test? You mean "write"? :)
> > >
> > > Cheers,
> > > Miquèl
> >
> > Hi Miquel,
> >
> > Should we us a atomic for the suspended variable?
>
> I haven't thought about it extensively, an atomic variable sound fine
> but I am definitely not a locking expert...
No need to use an atomic if the variable is already protected by a lock
when accessed, and this seems to be case.
>
> >
> > /Sean
> >
> > diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> > index b3a9bc08b4bb..eb4ec9a42d49 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -338,16 +338,19 @@ static int nand_isbad_bbm(struct nand_chip *chip, loff_t ofs)
> > *
> > * Return: -EBUSY if the chip has been suspended, 0 otherwise
You need to fix the documentation and make it clear that the caller
will be blocked if the chip is suspended.
> > */
> > -static int nand_get_device(struct nand_chip *chip)
> > +static void nand_get_device(struct nand_chip *chip)
> > {
> > - mutex_lock(&chip->lock);
> > - if (chip->suspended) {
> > + /* Wait until the device is resumed. */
> > + while (1) {
> > + mutex_lock(&chip->lock);
> > + if (!chip->suspended) {
> > + mutex_lock(&chip->controller->lock);
> > + return;
> > + }
> > mutex_unlock(&chip->lock);
> > - return -EBUSY;
> > - }
> > - mutex_lock(&chip->controller->lock);
> >
> > - return 0;
> > + wait_event(chip->resume_wq, !chip->suspended);
> > + }
> > }
> >
> > /**
> > @@ -576,9 +579,7 @@ static int nand_block_markbad_lowlevel(struct nand_chip *chip, loff_t ofs)
> > nand_erase_nand(chip, &einfo, 0);
> >
> > /* Write bad block marker to OOB */
> > - ret = nand_get_device(chip);
> > - if (ret)
> > - return ret;
> > + nand_get_device(chip);
> >
> > ret = nand_markbad_bbm(chip, ofs);
> > nand_release_device(chip);
> > @@ -3759,9 +3760,7 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
> > ops->mode != MTD_OPS_RAW)
> > return -ENOTSUPP;
> >
> > - ret = nand_get_device(chip);
> > - if (ret)
> > - return ret;
> > + nand_get_device(chip);
> >
> > if (!ops->datbuf)
> > ret = nand_do_read_oob(chip, from, ops);
> > @@ -4352,9 +4351,7 @@ static int nand_write_oob(struct mtd_info *mtd, loff_t to,
> >
> > ops->retlen = 0;
> >
> > - ret = nand_get_device(chip);
> > - if (ret)
> > - return ret;
> > + nand_get_device(chip);
> >
> > switch (ops->mode) {
> > case MTD_OPS_PLACE_OOB:
> > @@ -4414,9 +4411,7 @@ int nand_erase_nand(struct nand_chip *chip, struct erase_info *instr,
> > return -EIO;
> >
> > /* Grab the lock and see if the device is available */
> > - ret = nand_get_device(chip);
> > - if (ret)
> > - return ret;
> > + nand_get_device(chip);
> >
> > /* Shift to get first page */
> > page = (int)(instr->addr >> chip->page_shift);
> > @@ -4503,7 +4498,7 @@ static void nand_sync(struct mtd_info *mtd)
> > pr_debug("%s: called\n", __func__);
> >
> > /* Grab the lock and see if the device is available */
> > - WARN_ON(nand_get_device(chip));
> > + nand_get_device(chip);
> > /* Release it and go back */
> > nand_release_device(chip);
> > }
> > @@ -4520,9 +4515,7 @@ static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
> > int ret;
> >
> > /* Select the NAND device */
> > - ret = nand_get_device(chip);
> > - if (ret)
> > - return ret;
> > + nand_get_device(chip);
> >
> > nand_select_target(chip, chipnr);
> >
> > @@ -4593,6 +4586,8 @@ static void nand_resume(struct mtd_info *mtd)
> > __func__);
> > }
> > mutex_unlock(&chip->lock);
> > +
> > + wake_up_all(&chip->resume_wq);
> > }
> >
> > /**
> > @@ -5370,6 +5365,7 @@ static int nand_scan_ident(struct nand_chip *chip, unsigned int maxchips,
> > chip->cur_cs = -1;
> >
> > mutex_init(&chip->lock);
> > + init_waitqueue_head(&chip->resume_wq);
> >
> > /* Enforce the right timings for reset/detection */
> > chip->current_interface_config = nand_get_reset_interface_config();
> > diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
> > index b2f9dd3cbd69..248054560581 100644
> > --- a/include/linux/mtd/rawnand.h
> > +++ b/include/linux/mtd/rawnand.h
> > @@ -1294,6 +1294,7 @@ struct nand_chip {
> > /* Internals */
> > struct mutex lock;
> > unsigned int suspended : 1;
> > + wait_queue_head_t resume_wq;
> > int cur_cs;
> > int read_retries;
> > struct nand_secure_region *secure_regions;
>
>
> Thanks,
> Miquèl
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