Messages in this thread | | | From | "Tokunori Ikegami" <> | Subject | RE: Re: [PATCH] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer | Date | Fri, 8 Feb 2019 23:23:59 +0900 |
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Hi Przemek-san,
Thank you so much for your explanation.
> I have seen a case myself where a value was written, chip changed > state to "ready" but when I was reading the value was incorrect.
I also know the similar issues for the both buffer and word write. Both issues were able to reproduce the write error behavior. Note: The word write issue is able to reproduce now also.
Those were resolved by using chip_good() instead to check the state.
> This can happen as result of intermittent issue with flash. It is > hard to fall into scenario when testing on limited number of devices > but with large enough population you can see that.
If possible I would like to know the issue detail and its cause also.
> Another situation > is when a flash chip reaches its maximum number of writes. So for > example a chip is designed for 100k writes to a page. Once you > reach that number of writes you can have invalid data written to > flash but chip itself reports everything was good and switches to > "ready" state.
Yes I see.
Regards, Ikegami
> -----Original Message----- > From: linux-mtd [mailto:linux-mtd-bounces@lists.infradead.org] On Behalf > Of Sobon, Przemyslaw > Sent: Friday, February 8, 2019 8:51 AM > To: ikegami_to@yahoo.co.jp; Boris Brezillon > Cc: keescook@chromium.org; marek.vasut@gmail.com; > ikegami@allied-telesis.co.jp; richard@nod.at; > linux-kernel@vger.kernel.org; joakim.tjernlund@infinera.com; > linux-mtd@lists.infradead.org; computersforpeace@gmail.com; > dwmw2@infradead.org; Liu Jian > Subject: RE: Re: [PATCH] cfi: fix deadloop in cfi_cmdset_0002.c > do_write_buffer > > Hi Ikegami, > > I have seen a case myself where a value was written, chip changed > state to "ready" but when I was reading the value was incorrect. > This can happen as result of intermittent issue with flash. It is > hard to fall into scenario when testing on limited number of devices > but with large enough population you can see that. Another situation > is when a flash chip reaches its maximum number of writes. So for > example a chip is designed for 100k writes to a page. Once you > reach that number of writes you can have invalid data written to > flash but chip itself reports everything was good and switches to > "ready" state. > > Hope this explanation is clear. Please let me know. > > Regards, > Przemek > > > -----Original Message----- > > From: ikegami_to@yahoo.co.jp <ikegami_to@yahoo.co.jp> > > Sent: Thursday, February 7, 2019 3:00 PM > > > > Hi Przemek-san, > > > > Could you please explain the case detail that the value is written > incorrectly? > > I think that the value is only written correctly except a bug. > > > > Regards, > > Ikegami > > > > --- boris.brezillon@collabora.com wrote --- : > > > Hi Sobon, > > > > > > On Tue, 5 Feb 2019 22:28:44 +0000 > > > "Sobon, Przemyslaw" <psobon@amazon.com> wrote: > > > > > > > > From: Boris Brezillon <bbrezillon@kernel.org> > > > > > Sent: Sunday, February 3, 2019 12:35 AM > > > > > > +Przemyslaw > > > > > > > > > > > > On Fri, 1 Feb 2019 07:30:39 +0800 Liu Jian > > > > > > <liujian56@huawei.com> wrote: > > > > > > > > > > > > > In function do_write_buffer(), in the for loop, there is a > > > > > > > case > > > > > > > chip_ready() returns 1 while chip_good() returns 0, so it > > > > > > > never break the loop. > > > > > > > To fix this, chip_good() is enough and it should timeout if > it > > > > > > > stay bad for a while. > > > > > > > > > > > > Looks like Przemyslaw reported and fixed the same problem. > > > > > > > > > > > > > > > > > > > > Fixes: dfeae1073583(mtd: cfi_cmdset_0002: Change write buffer > > > > > > > to check correct value) > > > > > > > > > > > > Can you put the Fixes tag on a single, and the format is > > > > > > > > > > > > Fixes: <hash> ("message") > > > > > > > > > > > > > Signed-off-by: Yi Huaijie <yihuaijie@huawei.com> > > > > > > > Signed-off-by: Liu Jian <liujian56@huawei.com> > > > > > > > > > > > > [1]http://patchwork.ozlabs.org/patch/1025566/ > > > > > > > > > > > > > --- > > > > > > > drivers/mtd/chips/cfi_cmdset_0002.c | 6 +++--- > > > > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > > > > > > > > > diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c > > > > > > > b/drivers/mtd/chips/cfi_cmdset_0002.c > > > > > > > index 72428b6..818e94b 100644 > > > > > > > --- a/drivers/mtd/chips/cfi_cmdset_0002.c > > > > > > > +++ b/drivers/mtd/chips/cfi_cmdset_0002.c > > > > > > > @@ -1876,14 +1876,14 @@ static int __xipram > do_write_buffer(struct map_info *map, struct flchip *chip, > > > > > > > continue; > > > > > > > } > > > > > > > > > > > > > > - if (time_after(jiffies, timeo) && !chip_ready(map, > adr)) > > > > > > > - break; > > > > > > > - > > > > > > > if (chip_good(map, adr, datum)) { > > > > > > > xip_enable(map, chip, adr); > > > > > > > goto op_done; > > > > > > > } > > > > > > > > > > > > > > + if (time_after(jiffies, timeo)) > > > > > > > + break; > > > > > > > + > > > > > > > /* Latency issues. Drop the lock, wait a while and > retry */ > > > > > > > UDELAY(map, chip, adr, 1); > > > > > > > } > > > > > > > > > > > > > > > > BTW, the patch itself looks good to me. Ikegami, can you confirm > it does the right thing? > > > > > > > > > > Thanks, > > > > > > > > > > Boris > > > > > > > > > > > > > One comment to this patch. If value is written incorrectly quickly > > > > we will be stuck in the loop even though nothing is going to change. > > > > For example a value was written incorrectly after 1us, the loop was > > > > set to 1ms, function will return after 1ms, this solution is not > > > > optimized for performance. I considered same when working on this > change and decided to do it different way. > > > > > > Seems like you're right if we assume that checking for GOOD state does > > > not require a delay after the READY check, but if that's not the case > > > and an extra delay is actually required, you might end up with a BAD > > > status while it could have turned GOOD at some point with the 'check > > > only for GOOD state until we timeout' approach. > > > > > > TBH, I don't know how CFI flashes work, so I'll let you guys sort this > > > out. > > > > > > Regards, > > > > > > Boris > > > > > > ______________________________________________________ > > > Linux MTD discussion mailing list > > > http://lists.infradead.org/mailman/listinfo/linux-mtd/ > > > > > > > > ______________________________________________________ > Linux MTD discussion mailing list > http://lists.infradead.org/mailman/listinfo/linux-mtd/
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