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SubjectRe: [PATCH 0/3] mtd: core: protect access to mtd devices while in suspend
Hi Sean,

sean@geanix.com wrote on Wed, 20 Oct 2021 09:12:35 +0200:

> On Wed, Oct 20, 2021 at 09:00:58AM +0200, Boris Brezillon wrote:
> > On Wed, 20 Oct 2021 08:52:50 +0200
> > Boris Brezillon <boris.brezillon@collabora.com> wrote:
> >
>
> [ ... ]
> > > >
> > > > Hi Boris and Miquel,
> > > >
> > > > gpmi-nand.c sets NAND_SKIP_BBTSCAN so we won't get there and populate
> > > > suspend resume hooks :(
> > > > Guess there is other drivers that does the same thing...
> >
> > Actually, this version is even cleaner:
> >
> > diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> > index 3d6c6e880520..98c39b7f6279 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -6222,8 +6222,6 @@ static int nand_scan_tail(struct nand_chip *chip)
> > mtd->_sync = nand_sync;
> > mtd->_lock = nand_lock;
> > mtd->_unlock = nand_unlock;
> > - mtd->_suspend = nand_suspend;
> > - mtd->_resume = nand_resume;
> > mtd->_reboot = nand_shutdown;
> > mtd->_block_isreserved = nand_block_isreserved;
> > mtd->_block_isbad = nand_block_isbad;
> > @@ -6261,14 +6259,20 @@ static int nand_scan_tail(struct nand_chip *chip)
> > goto err_free_interface_config;
> >
> > /* Check, if we should skip the bad block table scan */
> > - if (chip->options & NAND_SKIP_BBTSCAN)
> > - return 0;
> > -
> > - /* Build bad block table */
> > - ret = nand_create_bbt(chip);
> > - if (ret)
> > - goto err_free_secure_regions;
> > + if (chip->options & NAND_SKIP_BBTSCAN) {
> > + /* Build bad block table */
> > + ret = nand_create_bbt(chip);
> > + if (ret)
> > + goto err_free_secure_regions;
> > + }
> >
> > + /*
> > + * Populate the suspend/resume hooks after the BBT has been scanned to
> > + * avoid using the suspend lock and resume waitqueue which are only
> > + * initialized when mtd_device_register() is called.
> > + */
> > + mtd->_suspend = nand_suspend;
> > + mtd->_resume = nand_resume;
> > return 0;
> >
> > err_free_secure_regions:
>
> Why is the gpmi-nand.c and other drivers set NAND_SKIP_BBTSCAN and then
> call nand_create_bbt() directly?
>
> To me it looks like legacy leftover...

It is...

885d71e5838f ("mtd: gpmi: fix the NULL pointer") added this flag to
avoid a NULL pointer dereference on chip->buffer->databuf on mx23,
which IIRC does not exist anymore.

I believe we could get rid of it. But anyway, I like the "cleanup"
proposed by Boris so IMHO you can add these two patches to the series.

Thanks,
Miquèl

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