Re: [RFC PATCH 1/2] mtd: nand: add nand_check_erased helper functions

[Andrea Scian]

Boris,

sorry for the later review.
I'm trying to run your patch on our systems. See below

Il 31/07/2015 09:10, Boris Brezillon ha scritto:
> On Thu, 30 Jul 2015 19:34:53 +0200
> Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> wrote:
>
> > Add two helper functions to help NAND controller drivers test whether a
> > specific NAND region is erased or not.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/mtd/nand/nand_base.c | 104 +++++++++++++++++++++++++++++++++++++++++++
> >   include/linux/mtd/nand.h     |   8 ++++
> >   2 files changed, 112 insertions(+)
> >
> > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> > index ceb68ca..1542ea7 100644
> > --- a/drivers/mtd/nand/nand_base.c
> > +++ b/drivers/mtd/nand/nand_base.c
> > @@ -1101,6 +1101,110 @@ out:
> >   EXPORT_SYMBOL(nand_lock);
> >
> >   /**
> > + * nand_check_erased_buf - check if a buffer contains (almost) only 0xff data
> > + * @buf: buffer to test
> > + * @len: buffer length
> > + * @bitflips_threshold:maximum number of bitflips
> > + *
> > + * Check if a buffer contains only 0xff, which means the underlying region
> > + * has been erased and is ready to be programmed.
> > + * The bitflips_threshold specify the maximum number of bitflips before
> > + * considering the region is not erased.
> > + * Note: The logic of this function has been extracted from the memweight
> > + * implementation, except that nand_check_erased_buf function exit before
> > + * testing the whole buffer if the number of bitflips exceed the
> > + * bitflips_threshold value.
> > + *
> > + * Returns a positive number of bitflips or -ERROR_CODE.
> > + */
> > +int nand_check_erased_buf(void *buf, int len, int bitflips_threshold)
> > +{
> > +	const unsigned char *bitmap = buf;
> > +	int bitflips = 0;
> > +	int weight;
> > +	int longs;
> > +
> > +	for (; len && ((unsigned long)bitmap) % sizeof(long);
> > +	     len--, bitmap++) {
> > +		weight = hweight8(*bitmap);
> > +
> > +		bitflips += sizeof(u8) - weight;

I think the above like should be

bitflips += sizeof(u8)*BITS_PER_BYTE - weight;


> > +		if (bitflips > bitflips_threshold)
> > +			return -EINVAL;
> > +	}
> > +
> > +
> > +	for (longs = len / sizeof(long); longs;
> > +	     longs--, bitmap += sizeof(long)) {
> > +		BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
> > +		weight = hweight_long(*((unsigned long *)bitmap));
> > +
> > +		bitflips += sizeof(long) - weight;

as above:

bitflips += sizeof(long)*BITS_PER_BYTE - weight;

> > +		if (bitflips > bitflips_threshold)
> > +			return -EINVAL;
> > +	}
> > +
> > +	len %= sizeof(long);
> > +
> > +	for (; len > 0; len--, bitmap++) {
> > +		weight = hweight8(*bitmap);
> > +		bitflips += sizeof(u8) - weight;


as above:

bitflips += sizeof(u8)*BITS_PER_BYTE - weight;


> > +	}
> > +
> > +	return bitflips;
> > +}
> > +EXPORT_SYMBOL(nand_check_erased_buf);
> > +
> > +/**
> > + * nand_check_erased_ecc_chunk - check if an ECC chunk contains (almost) only
> > + *				 0xff data
> > + * @data: data buffer to test
> > + * @datalen: data length
> > + * @ecc: ECC buffer
> > + * @ecclen: ECC length
> > + * @extraoob: extra OOB buffer
> > + * @extraooblen: extra OOB length
> > + * @bitflips_threshold: maximum number of bitflips
> > + *
> > + * Check if a data buffer and its associated ECC and OOB data contains only
> > + * 0xff pattern, which means the underlying region has been erased and is
> > + * ready to be programmed.
> > + * The bitflips_threshold specify the maximum number of bitflips before
> > + * considering the region as not erased.
> > + *
> > + * Returns a positive number of bitflips or -ERROR_CODE.
> > + */
> > +int nand_check_erased_ecc_chunk(void *data, int datalen,
> > +				void *ecc, int ecclen,
> > +				void *extraoob, int extraooblen,
> > +				int bitflips_threshold)
> > +{
> > +	int bitflips = 0;
> > +	int ret;
> > +
> > +	ret = nand_check_erased_buf(data, datalen, bitflips_threshold);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	bitflips += ret;
> > +	bitflips_threshold -= ret;
> > +
> > +	ret = nand_check_erased_buf(ecc, ecclen, bitflips_threshold);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	bitflips += ret;
> > +	bitflips_threshold -= ret;
> > +
> > +	ret = nand_check_erased_buf(extraoob, extraooblen, bitflips_threshold);
> > +	if (ret < 0)
> > +		return ret;
> > +
>
> Forgot the memset operations here:
>
> 	memset(data, 0xff, datalen);
> 	memset(ecc, 0xff, ecclen);
> 	memset(extraoob, 0xff, extraooblen);
>
> > +	return bitflips + ret;
> > +}
> > +EXPORT_SYMBOL(nand_check_erased_ecc_chunk);
> > +
> > +/**
> >    * nand_read_page_raw - [INTERN] read raw page data without ecc
> >    * @mtd: mtd info structure
> >    * @chip: nand chip info structure
> > diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> > index 272f429..ae06a07 100644
> > --- a/include/linux/mtd/nand.h
> > +++ b/include/linux/mtd/nand.h
> > @@ -1030,4 +1030,12 @@ struct nand_sdr_timings {
> >
> >   /* get timing characteristics from ONFI timing mode. */
> >   const struct nand_sdr_timings *onfi_async_timing_mode_to_sdr_timings(int mode);
> > +
> > +int nand_check_erased_buf(void *data, int datalen,
> > +			  int threshold);
> > +
> > +int nand_check_erased_ecc_chunk(void *data, int datalen,
> > +				void *ecc, int ecclen,
> > +				void *extraoob, int extraooblen,
> > +				int threshold);
> >   #endif /* __LINUX_MTD_NAND_H */
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/