Re: RE: [PATCH] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer

[<ikegami_to@xxxxxxxxxxx>]

The patch looks good to me.
About the performance issue it seems that it is expected by this do_write_buffer() function.
If this patch will be applied I will do rebase my patches with this.

Reviewed-by: Tokunori Ikegami <ikegami_to@xxxxxxxxxxx>


--- psobon@xxxxxxxxxx wrote --- :
> > From: Boris Brezillon <bbrezillon@xxxxxxxxxx> 
> > Sent: Sunday, February 3, 2019 12:35 AM
> > > +Przemyslaw
> > > 
> > > On Fri, 1 Feb 2019 07:30:39 +0800
> > > Liu Jian <liujian56@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > > Signed-off-by: Liu Jian <liujian56@xxxxxxxxxx>
> > > 
> > > [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.
> 
> Regards,
> Przemek
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/ 
> 


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