[PATCH skiboot/pflash] libflash/libffs: Detect first byte flash corruption

[Cyril Bur]

On Fri, 2017-06-30 at 15:34 +0200, Cédric Le Goater wrote:
> On 06/29/2017 12:40 AM, Cyril Bur wrote:
> > This patch is not for upstream but currently this unknown corruption is
> > making life difficult.
> 
> From what I have seen on a couple of affected systems, the data is 
> not corrupted but it's the first byte read which is bogus. After a
> reboot, all comes back to normal. 

Interesting. Especially since there is no corruption, depending on how
long this hangs around for this patch might be useful.

> 
> So we might have an issue with the optimize read settings and/or 
> fast-read. This is difficult to corner. 
> 
> Has anyone seen this issue on the openbmc 4.7 kernel ? 
>  

Have you ever seen it on a ast2400 or is it always ast2500?

> Thanks,
> 
> C.
> 
> 
> > Perhaps it can be useful at least temporarily.
> > 
> > Feel free to remove the option to continue and leave just the
> > information message.
> > 
> > Signed-off-by: Cyril Bur <cyril.bur at au1.ibm.com>
> > ---
> >  libflash/libffs.c | 29 +++++++++++++++++++++++++++++
> >  1 file changed, 29 insertions(+)
> > 
> > diff --git a/libflash/libffs.c b/libflash/libffs.c
> > index 7ae9050e..dce6237e 100644
> > --- a/libflash/libffs.c
> > +++ b/libflash/libffs.c
> > @@ -260,6 +260,35 @@ int ffs_init(uint32_t offset, uint32_t max_size, struct blocklevel_device *bl,
> >  
> >  	/* Convert and check flash header */
> >  	rc = ffs_check_convert_header(&f->hdr, &raw_hdr);
> > +	/*
> > +	 * A bug on witherspoon of currently unknown origin causes
> > +	 * corruption of the first byte of flash. This is by no means
> > +	 * a fix and should never go upstream but may prove helpful.
> > +	 */
> > +	if (rc == FFS_ERR_BAD_MAGIC) {
> > +		/*
> > +		 * We can set the first byte to what we know it should be
> > +		 * and try to check and convert header again. If it
> > +		 * succeeds there is a very high chance this is the
> > +		 * problem.
> > +		 */
> > +		*(char *)&raw_hdr = 'P';
> > +		rc = ffs_check_convert_header(&f->hdr, &raw_hdr);
> > +		if (rc) {
> > +			/*
> > +			 * Turn it back into BAD_MAGIC, the flash obviously
> > +			 * has bigger problems.
> > +			 */
> > +			rc = FFS_ERR_BAD_MAGIC;
> > +		} else {
> > +			FL_ERR("FFS: Detected corruption of the first byte of flash.\n");
> > +			FL_ERR("     Recommend hard power cycling the entire machine\n");
> > +			FL_ERR("     Continuing is dangerous!\n");
> > +			FL_ERR("     Continuing in 10 seconds\n");
> > +			sleep(10);
> > +			rc = 0;
> > +		}
> > +	}
> >  	if (rc) {
> >  		FL_INF("FFS: Flash header not found. Code: %d\n", rc);
> >  		goto out;
> > 
> 
>