[V3, 1/2] mtd: brcmnand: Add check for erased page bitflips

[V3, 1/2] mtd: brcmnand: Add check for erased page bitflips

[Kamal Dasu]

Check for erased page bitflips in a page. And if well within
threshold return data as all 0xff. Apply sw check for controller
version < 7.2. Controller vesion >= 7.2 has hw support.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
---
V3 changes
 Return the max bitflips from a sector within a page
V2 changes 
 Added use of nand_check_erased_ecc_chunk
 Restrict change to older controller < 7.2
---

 drivers/mtd/nand/brcmnand/brcmnand.c | 62 ++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
index b76ad7c..7ee9617 100644
--- a/drivers/mtd/nand/brcmnand/brcmnand.c
+++ b/drivers/mtd/nand/brcmnand/brcmnand.c
@@ -1545,6 +1545,56 @@ static int brcmnand_read_by_pio(struct mtd_info *mtd, struct nand_chip *chip,
 	return ret;
 }
 
+/*
+ * Check a page to see if it is erased (w/ bitflips) after an uncorrectable ECC
+ * error
+ *
+ * Because the HW ECC signals an ECC error if an erase paged has even a single
+ * bitflip, we must check each ECC error to see if it is actually an erased
+ * page with bitflips, not a truly corrupted page.
+ *
+ * On a real error, return a negative error code (-EBADMSG for ECC error), and
+ * buf will contain raw data.
+ * Otherwise, buf gets filled with 0xffs and return the maximum number of
+ * bitflips-per-ECC-sector to the caller.
+ *
+ */
+static int brcmstb_nand_verify_erased_page(struct mtd_info *mtd,
+		  struct nand_chip *chip, void *buf, u64 addr)
+{
+	int i, sas;
+	void *oob = chip->oob_poi;
+	int bitflips = 0;
+	int page = addr >> chip->page_shift;
+	int ret;
+
+	if (!buf) {
+		buf = chip->buffers->databuf;
+		/* Invalidate page cache */
+		chip->pagebuf = -1;
+	}
+
+	sas = mtd->oobsize / chip->ecc.steps;
+
+	/* read without ecc for verification */
+	chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
+	ret = chip->ecc.read_page_raw(mtd, chip, buf, true, page);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < chip->ecc.steps; i++, oob += sas) {
+		ret = nand_check_erased_ecc_chunk(buf, chip->ecc.size,
+						  oob, sas, NULL, 0,
+						  chip->ecc.strength);
+		if (ret < 0)
+			return ret;
+
+		bitflips = max(bitflips, ret);
+	}
+
+	return bitflips;
+}
+
 static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
 			 u64 addr, unsigned int trans, u32 *buf, u8 *oob)
 {
@@ -1575,6 +1625,18 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
 	}
 
 	if (mtd_is_eccerr(err)) {
+		/*
+		 * Controller version 7.2 has hw encoder to detect erased page
+		 * bitflips, apply sw verification for older controllers only
+		 */
+		if (ctrl->nand_version < 0x0702) {
+			err = brcmstb_nand_verify_erased_page(mtd, chip, buf,
+							      addr);
+			/* erased page bitflips corrected */
+			if (err > 0)
+				return err;
+		}
+
 		dev_dbg(ctrl->dev, "uncorrectable error at 0x%llx\n",
 			(unsigned long long)err_addr);
 		mtd->ecc_stats.failed++;
-- 
1.9.1

[V3, 2/2] mtd: brcmnand: Detect sticky ucorr ecc error on dma reads

[Kamal Dasu]

This change provides a fix for controller bug where nand
controller could have a possible sticky error after a PIO
followed by a DMA read. The fix retries a read if we see
a uncorr_ecc after read to detect such sticky errors.
The fix applies to only controller version 7.0 and 7.1.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
---
V3 changes 
 none
V2 Changes 
 Restrict controller bug workaround to version 7.0 and 7.1
---
 drivers/mtd/nand/brcmnand/brcmnand.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
index 7ee9617..1156495 100644
--- a/drivers/mtd/nand/brcmnand/brcmnand.c
+++ b/drivers/mtd/nand/brcmnand/brcmnand.c
@@ -1602,9 +1602,11 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
 	struct brcmnand_controller *ctrl = host->ctrl;
 	u64 err_addr = 0;
 	int err;
+	static bool retry = true;
 
 	dev_dbg(ctrl->dev, "read %llx -> %p\n", (unsigned long long)addr, buf);
 
+try_dmaread:
 	brcmnand_write_reg(ctrl, BRCMNAND_UNCORR_COUNT, 0);
 
 	if (has_flash_dma(ctrl) && !oob && flash_dma_buf_ok(buf)) {
@@ -1626,6 +1628,22 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
 
 	if (mtd_is_eccerr(err)) {
 		/*
+		 * On controller version and 7.0, 7.1 , DMA read after a
+		 * prior PIO read that reported uncorrectable error,
+		 * the DMA engine captures this error following DMA read
+		 * cleared only on subsequent DMA read, so just retry once
+		 * to clear a possible false error reported for current DMA
+		 * read
+		 */
+		if ((ctrl->nand_version == 0x0700) ||
+		    (ctrl->nand_version == 0x0701)) {
+			if (retry) {
+				retry = false;
+				goto try_dmaread;
+			}
+		}
+
+		/*
 		 * Controller version 7.2 has hw encoder to detect erased page
 		 * bitflips, apply sw verification for older controllers only
 		 */
-- 
1.9.1

Re: [V3, 2/2] mtd: brcmnand: Detect sticky ucorr ecc error on dma reads

[Brian Norris]

Hi,

Looking through Boris's pull request, I noticed an issue:

On Thu, Jun 09, 2016 at 05:17:55PM -0400, Kamal Dasu wrote:
> This change provides a fix for controller bug where nand
> controller could have a possible sticky error after a PIO
> followed by a DMA read. The fix retries a read if we see
> a uncorr_ecc after read to detect such sticky errors.
> The fix applies to only controller version 7.0 and 7.1.
> 
> Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
> ---
> V3 changes 
>  none
> V2 Changes 
>  Restrict controller bug workaround to version 7.0 and 7.1
> ---
>  drivers/mtd/nand/brcmnand/brcmnand.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
> index 7ee9617..1156495 100644
> --- a/drivers/mtd/nand/brcmnand/brcmnand.c
> +++ b/drivers/mtd/nand/brcmnand/brcmnand.c
> @@ -1602,9 +1602,11 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
>  	struct brcmnand_controller *ctrl = host->ctrl;
>  	u64 err_addr = 0;
>  	int err;
> +	static bool retry = true;

Is this intentionally static? That means your retry will only be
performed exactly once *ever*. Probably not what you expected?

Boris, if this is indeed unintended, would you rather fix this up in the
original patch and send me a new pull request? Or have my apply the
trivial fixup (i.e., s/static//) as a separate patch on top?

Brian

>  
>  	dev_dbg(ctrl->dev, "read %llx -> %p\n", (unsigned long long)addr, buf);
>  
> +try_dmaread:
>  	brcmnand_write_reg(ctrl, BRCMNAND_UNCORR_COUNT, 0);
>  
>  	if (has_flash_dma(ctrl) && !oob && flash_dma_buf_ok(buf)) {
> @@ -1626,6 +1628,22 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
>  
>  	if (mtd_is_eccerr(err)) {
>  		/*
> +		 * On controller version and 7.0, 7.1 , DMA read after a
> +		 * prior PIO read that reported uncorrectable error,
> +		 * the DMA engine captures this error following DMA read
> +		 * cleared only on subsequent DMA read, so just retry once
> +		 * to clear a possible false error reported for current DMA
> +		 * read
> +		 */
> +		if ((ctrl->nand_version == 0x0700) ||
> +		    (ctrl->nand_version == 0x0701)) {
> +			if (retry) {
> +				retry = false;
> +				goto try_dmaread;
> +			}
> +		}
> +
> +		/*
>  		 * Controller version 7.2 has hw encoder to detect erased page
>  		 * bitflips, apply sw verification for older controllers only
>  		 */
> -- 
> 1.9.1
> 

Re: [V3, 2/2] mtd: brcmnand: Detect sticky ucorr ecc error on dma reads

[Boris Brezillon]

On Sun, 10 Jul 2016 22:04:52 -0700
Brian Norris <computersforpeace@gmail.com> wrote:

> Hi,
> 
> Looking through Boris's pull request, I noticed an issue:
> 
> On Thu, Jun 09, 2016 at 05:17:55PM -0400, Kamal Dasu wrote:
> > This change provides a fix for controller bug where nand
> > controller could have a possible sticky error after a PIO
> > followed by a DMA read. The fix retries a read if we see
> > a uncorr_ecc after read to detect such sticky errors.
> > The fix applies to only controller version 7.0 and 7.1.
> > 
> > Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
> > ---
> > V3 changes 
> >  none
> > V2 Changes 
> >  Restrict controller bug workaround to version 7.0 and 7.1
> > ---
> >  drivers/mtd/nand/brcmnand/brcmnand.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
> > index 7ee9617..1156495 100644
> > --- a/drivers/mtd/nand/brcmnand/brcmnand.c
> > +++ b/drivers/mtd/nand/brcmnand/brcmnand.c
> > @@ -1602,9 +1602,11 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
> >  	struct brcmnand_controller *ctrl = host->ctrl;
> >  	u64 err_addr = 0;
> >  	int err;
> > +	static bool retry = true;  
> 
> Is this intentionally static? That means your retry will only be
> performed exactly once *ever*. Probably not what you expected?
> 
> Boris, if this is indeed unintended, would you rather fix this up in the
> original patch and send me a new pull request?

I'll fix the initial commit and send a new PR once Kamal has confirmed
this variable should not be static (which is also my opinion).

> Or have my apply the
> trivial fixup (i.e., s/static//) as a separate patch on top?

Thanks,

Boris

Re: [V3, 2/2] mtd: brcmnand: Detect sticky ucorr ecc error on dma reads

[Kamal Dasu]

It's ok to fix it up.

Kamal

On Mon, Jul 11, 2016 at 2:49 AM, Boris Brezillon
<boris.brezillon@free-electrons.com> wrote:
> On Sun, 10 Jul 2016 22:04:52 -0700
> Brian Norris <computersforpeace@gmail.com> wrote:
>
>> Hi,
>>
>> Looking through Boris's pull request, I noticed an issue:
>>
>> On Thu, Jun 09, 2016 at 05:17:55PM -0400, Kamal Dasu wrote:
>> > This change provides a fix for controller bug where nand
>> > controller could have a possible sticky error after a PIO
>> > followed by a DMA read. The fix retries a read if we see
>> > a uncorr_ecc after read to detect such sticky errors.
>> > The fix applies to only controller version 7.0 and 7.1.
>> >
>> > Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
>> > ---
>> > V3 changes
>> >  none
>> > V2 Changes
>> >  Restrict controller bug workaround to version 7.0 and 7.1
>> > ---
>> >  drivers/mtd/nand/brcmnand/brcmnand.c | 18 ++++++++++++++++++
>> >  1 file changed, 18 insertions(+)
>> >
>> > diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
>> > index 7ee9617..1156495 100644
>> > --- a/drivers/mtd/nand/brcmnand/brcmnand.c
>> > +++ b/drivers/mtd/nand/brcmnand/brcmnand.c
>> > @@ -1602,9 +1602,11 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
>> >     struct brcmnand_controller *ctrl = host->ctrl;
>> >     u64 err_addr = 0;
>> >     int err;
>> > +   static bool retry = true;
>>
>> Is this intentionally static? That means your retry will only be
>> performed exactly once *ever*. Probably not what you expected?
>>
>> Boris, if this is indeed unintended, would you rather fix this up in the
>> original patch and send me a new pull request?
>
> I'll fix the initial commit and send a new PR once Kamal has confirmed
> this variable should not be static (which is also my opinion).
>
>> Or have my apply the
>> trivial fixup (i.e., s/static//) as a separate patch on top?
>
> Thanks,
>
> Boris



-- 
Kamal Dasu
Principal Engineer | Broadcom Ltd. 200 Brickstone Sq Andover | 978-719-1405

Re: [V3, 1/2] mtd: brcmnand: Add check for erased page bitflips

[Boris Brezillon]

On Thu,  9 Jun 2016 17:17:54 -0400
Kamal Dasu <kdasu.kdev@gmail.com> wrote:

> Check for erased page bitflips in a page. And if well within
> threshold return data as all 0xff. Apply sw check for controller
> version < 7.2. Controller vesion >= 7.2 has hw support.
> 
> Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>

Applied both.

Thanks,

Boris

> ---
> V3 changes
>  Return the max bitflips from a sector within a page
> V2 changes 
>  Added use of nand_check_erased_ecc_chunk
>  Restrict change to older controller < 7.2
> ---
> 
>  drivers/mtd/nand/brcmnand/brcmnand.c | 62 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 62 insertions(+)
> 
> diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
> index b76ad7c..7ee9617 100644
> --- a/drivers/mtd/nand/brcmnand/brcmnand.c
> +++ b/drivers/mtd/nand/brcmnand/brcmnand.c
> @@ -1545,6 +1545,56 @@ static int brcmnand_read_by_pio(struct mtd_info *mtd, struct nand_chip *chip,
>  	return ret;
>  }
>  
> +/*
> + * Check a page to see if it is erased (w/ bitflips) after an uncorrectable ECC
> + * error
> + *
> + * Because the HW ECC signals an ECC error if an erase paged has even a single
> + * bitflip, we must check each ECC error to see if it is actually an erased
> + * page with bitflips, not a truly corrupted page.
> + *
> + * On a real error, return a negative error code (-EBADMSG for ECC error), and
> + * buf will contain raw data.
> + * Otherwise, buf gets filled with 0xffs and return the maximum number of
> + * bitflips-per-ECC-sector to the caller.
> + *
> + */
> +static int brcmstb_nand_verify_erased_page(struct mtd_info *mtd,
> +		  struct nand_chip *chip, void *buf, u64 addr)
> +{
> +	int i, sas;
> +	void *oob = chip->oob_poi;
> +	int bitflips = 0;
> +	int page = addr >> chip->page_shift;
> +	int ret;
> +
> +	if (!buf) {
> +		buf = chip->buffers->databuf;
> +		/* Invalidate page cache */
> +		chip->pagebuf = -1;
> +	}
> +
> +	sas = mtd->oobsize / chip->ecc.steps;
> +
> +	/* read without ecc for verification */
> +	chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
> +	ret = chip->ecc.read_page_raw(mtd, chip, buf, true, page);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < chip->ecc.steps; i++, oob += sas) {
> +		ret = nand_check_erased_ecc_chunk(buf, chip->ecc.size,
> +						  oob, sas, NULL, 0,
> +						  chip->ecc.strength);
> +		if (ret < 0)
> +			return ret;
> +
> +		bitflips = max(bitflips, ret);
> +	}
> +
> +	return bitflips;
> +}
> +
>  static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
>  			 u64 addr, unsigned int trans, u32 *buf, u8 *oob)
>  {
> @@ -1575,6 +1625,18 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
>  	}
>  
>  	if (mtd_is_eccerr(err)) {
> +		/*
> +		 * Controller version 7.2 has hw encoder to detect erased page
> +		 * bitflips, apply sw verification for older controllers only
> +		 */
> +		if (ctrl->nand_version < 0x0702) {
> +			err = brcmstb_nand_verify_erased_page(mtd, chip, buf,
> +							      addr);
> +			/* erased page bitflips corrected */
> +			if (err > 0)
> +				return err;
> +		}
> +
>  		dev_dbg(ctrl->dev, "uncorrectable error at 0x%llx\n",
>  			(unsigned long long)err_addr);
>  		mtd->ecc_stats.failed++;



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com