linux-kernel - Re: [PATCH v10 10/10] mtd: maps: gpio-addr-flash: Add support for device-tree devices

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Message-ID: <20181005182931.172b8f1c@bbrezillon>
Date:   Fri, 5 Oct 2018 18:29:31 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Zhouyang Jia <jiazhouyang09@...il.com>,
        linux-mtd@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 10/10] mtd: maps: gpio-addr-flash: Add support for
 device-tree devices

On Fri, 5 Oct 2018 17:40:44 +0200
Ricardo Ribalda Delgado <ricardo.ribalda@...il.com> wrote:

> Hi Boris
> On Fri, Oct 5, 2018 at 4:52 PM Boris Brezillon
> <boris.brezillon@...tlin.com> wrote:
> >
> > On Fri, 5 Oct 2018 16:06:57 +0200
> > Ricardo Ribalda Delgado <ricardo.ribalda@...il.com> wrote:
> >  
> > > Hi again Boris
> > >
> > >
> > > On Fri, Oct 5, 2018 at 2:10 PM Boris Brezillon
> > > <boris.brezillon@...tlin.com> wrote:  
> > > >
> > > > On Fri, 5 Oct 2018 14:04:52 +0200
> > > > Ricardo Ribalda Delgado <ricardo.ribalda@...il.com> wrote:
> > > >  
> > > > > Hi Boris
> > > > > On Fri, Oct 5, 2018 at 12:12 PM Boris Brezillon
> > > > > <boris.brezillon@...tlin.com> wrote:  
> > > > > >
> > > > > > On Fri, 5 Oct 2018 11:54:18 +0200
> > > > > > Ricardo Ribalda Delgado <ricardo.ribalda@...il.com> wrote:
> > > > > >  
> > > > > > > Hi Boris
> > > > > > >
> > > > > > > Just seen that  you already did the rebase at
> > > > > > > https://github.com/bbrezillon/linux-0day/commits/mtd/physmap-cleanup
> > > > > > >
> > > > > > > Thanks for that.
> > > > > > >
> > > > > > > I am about to test it in real hw (unless you want me wait)  
> > > > > >
> > > > > > Sure, go ahead and test it.
> > > > > >
> > > > > > Thanks,
> > > > > >
> > > > > > Boris  
> > > > > I had to change this on your patchset to have it working on hw:
> > > > > https://pastebin.com/78A7yhJ9
> > > > >
> > > > > If you send the patchset to the mailing list I can review it patch by patch.
> > > > >
> > > > > Also
> > > > > mtd: maps: Prepare merging of physmap and physmap_of
> > > > >
> > > > > I do not think that can be bisected. (Not sure, I have to test it)  
> > > >
> > > > Okay, I'll have a look.
> > > >  
> > > > >
> > > > > I add the diff to the mail, but gmail will probably scramble the
> > > > > lines(yes I know I have to use other mail client)  
> > > >
> > > > The diff looks good, I'll fix that an send a push a new version.  
> > >
> > > Also fix on physmap_flash_remove
> > >
> > > physmap_data->exit(dev); must be called BEFORE
> > > map_destroy(info->mtds[i]);  
> >
> > Hm, that's weird. That shouldn't happen. Do you have a non-NULL  
> > ->exit()? Can you detail why you think ->exit() call is the cause of  
> > this OOPS?
> >  
> 
> No idea.  It was crashing at:
> https://github.com/bbrezillon/linux-0day/blob/mtd/physmap-cleanup/drivers/mtd/chips/cfi_cmdset_0002.c#L2839
> cfi_cmdset_0002.c seesm to play with cfi->chips on its reset callback
> 
> I added some printfs:
> 
> if (!cfi),
> if (!chip)
> if (!cfi->chips)
> 
> sometimes it crashed on one place, sometimes in another :S. Reading
> back our patch it seemed more logical (semantically :P) to
> destroy after exit and not the other way around.

Actually no, it makes more sense to call ->exit() after destroying the
maps, because the platform-specific ->exit() implem might release
resources that are used during the destroy_map() operation. Another
reason to keep it in this order is that operations in the remove path
should be in the reverse order of those done in the probe path, and
->init() is definitely called before map_probe().

> 
> I made that change and it stopped OOPsing at reboot.

Maybe it's just a side effect, especially since I'm pretty sure your
physmap_data->exit() is NULL (assuming you do use DT to declare your
flash).

> 
> Havent had the time to dig deeper. But if it does not break anything
> on your side to invert destroy and exit please do so. It was not
> oopsing with my patchset.

I'd like to understand what's happening before doing this change. As I
said, I fear this reordering just hides something else.