[PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
On NAND flash devices, UBI reserves some physical erase blocks (PEB) for
bad block handling.
Today, the number of reserved PEB can only be set as a percentage of the
total number of PEB in each MTD partition.
For example, for a NAND flash with 128KiB PEB, 2 MTD partition of 20MiB
(mtd0) and 100MiB (mtd1) and 2% reserved PEB:
- the UBI device on mtd0 will have 2 PEB reserved
- the UBI device on mtd1 will have 16 PEB reserved
The problem with this behaviour is that NAND flash manufacturers give a
minimum number of valid block (NVB) during the endurance life of the
device.
E.G.:
Parameter SymbolMinMaxUnit Notes
--
Valid block number NVB 10041024 Blocks 1
Note:
1. Invalid blocks are block that contain one or more bad bits beyond
ECC. The device may contain bad blocks upon shipment. Additional bad
blocks may develop over time; however, the total number of available
blocks will not drop below NVB during the endurance life of the device.
>From this number we can deduce the maximum number of bad PEB that a
device will contain during its endurance life :
A 128MiB NAND flash (1024 PEB) will not have less than 20 bad blocks
during the flash endurance life.
BUT, the manufacturer doesn't tell where those bad block will appear. He
doesn't say either if they will be equally disposed on the whole device
(and I'm pretty sure they won't).
So, according to the datasheets, we should reserve the maximum number of
bad PEB for each UBI device.
(Worst case scenario: 20 bad blocks appears on the smallest MTD
partition.)
So this patch make UBI use the whole MTD device size to calculate the
Maximum bad expected eraseblocks.
The Kconfig option is in per1024 blocks, thus it can have a default
value of 20 which is *very* common for NAND devices.
Signed-off-by: Richard Genoud
---
drivers/mtd/ubi/Kconfig | 14 ++
drivers/mtd/ubi/build.c | 17 ++---
2 files changed, 24 insertions(+), 7 deletions(-)
diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index 145cda2..b77ffe1 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -28,15 +28,21 @@ config MTD_UBI_WL_THRESHOLD
to 128 or 256, although it does not have to be power of 2).
config MTD_UBI_BEB_LIMIT
- int "Percentage of maximum expected bad eraseblocks"
- default 2
- range 0 25
+ int "Maximum expected bad eraseblocks per 1024 eraseblocks"
+ default 20
+ range 2 256
help
If the MTD device admits of bad eraseblocks (e.g. NAND flash), UBI
reserves some amount of physical eraseblocks to handle new bad
eraseblocks.
This option specifies the maximum bad eraseblocks UBI expects on the
- ubi device (percents of total number of flash eraseblocks).
+ ubi device per 1024 eraseblocks.
+ This value is often given in an other form in the NAND datasheet
+ (min NVB i.e. minimal number of valid blocks). The maximum expected
+ bad eraseblocks per 1024 is then:
+ 1024 * (1 - MinNVB / MaxNVB)
+ Which gives 20 for most NAND devices.
+
This limit is used in order to derive amount of eraseblock UBI
reserves for handling new bad blocks.
If the device has more bad eraseblocks than this limit, UBI does not
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 62cc6ce..87b39c2 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -36,6 +36,7 @@
#include
#include
#include
+#include
#include
#include
#include
@@ -610,12 +611,22 @@ static int io_init(struct ubi_device *ubi)
if (mtd_can_have_bb(ubi->mtd)) {
ubi->bad_allowed = 1;
if (CONFIG_MTD_UBI_BEB_LIMIT > 0) {
- int percent = CONFIG_MTD_UBI_BEB_LIMIT;
+ int per1024 = CONFIG_MTD_UBI_BEB_LIMIT;
+ int device_peb_count;
+ uint64_t device_size;
int beb_limit;
- beb_limit = mult_frac(ubi->peb_count, percent, 100);
+ /* we are using here the whole MTD device size and not
+* the MTD partition size because the maximum number of
+* bad blocks is a percentage of the whole device and
+* the bad blocks are not fairly disposed on a flash
+* device
+*/
+ device_size = mtd_get_device_size(ubi->mtd);
+ device_peb_count = mtd_div_by_eb(device_size, ubi->mtd);
+ beb_limit = mult_frac(device_peb_count, per1024, 1024);
/* round it up */
- if (mult_frac(beb_limit, 100, percent) < ubi->peb_count)
+ if (mult_frac(beb_limit, 1024, per1024) <
ubi->peb
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
On Tue, 2012-07-10 at 18:23 +0200, Richard Genoud wrote: > > The Kconfig option is in per1024 blocks, thus it can have a default > value of 20 which is *very* common for NAND devices. Why do you prefer per1024? I'd make it centi-percent instead, wouldn't that be more human-friendly. It is just %*100. If I am a user, it is easy for me to calculate % and multiply that by 100. This per1024 thing would make me scratch my head... -- Best Regards, Artem Bityutskiy signature.asc Description: This is a digitally signed message part
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
2012/7/18 Artem Bityutskiy : > On Tue, 2012-07-10 at 18:23 +0200, Richard Genoud wrote: >> >> The Kconfig option is in per1024 blocks, thus it can have a default >> value of 20 which is *very* common for NAND devices. > > Why do you prefer per1024? I'd make it centi-percent instead, wouldn't > that be more human-friendly. It is just %*100. If I am a user, it is > easy for me to calculate % and multiply that by 100. This per1024 thing > would make me scratch my head... All the NAND devices I've seen are a multiple of 1024 erase blocks, so I thought it'll be easier for the humans to use per1024... here are 2 random datasheets : page 14: http://www.micron.com/~/media/Documents/Products/Data%20Sheet/NAND%20Flash/6691NANDXXX%20A%20128Mb_256Mb_528%20byte_or_264%20word_page_3V_SLC_90nm.pdf 2048 blocks 40BEB max => 20per1024 1024 blocks 20BEB max => 20per1024 page 24: http://www.hynix.com/datasheet/pdf/flash/HY27(U_S)S(08_16)121M(Rev0.6).pdf 4096 blocks 80BEB max => 20per1024 If we express the default exact value of 20 per1024 blocks in percent, that would be 1.953125% (event in per-thousand, we'll have 19.53125). => the value have to be rounded to floor or ceiling and that will make the user unsure about the effective number of bad blocks used for bad block handling. (even if we say that the default value 20 per-thousand block will be used, as the NAND devices have a number of blocks multiple of 1024, for a 4096 blocks device, we'll have 81.92 reserved blocks, rounded to 82 => we loose 2 blocks for each mtd partition.) So the per1024 thing was really to stick to the device layout and to be easier for users (IMHO) Richard. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
On Wed, 2012-07-18 at 10:30 +0200, Richard Genoud wrote: > So the per1024 thing was really to stick to the device layout and to > be easier for users (IMHO) Convinced, thanks! -- Best Regards, Artem Bityutskiy signature.asc Description: This is a digitally signed message part
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
On Tue, 2012-07-10 at 18:23 +0200, Richard Genoud wrote: > + /* we are using here the whole MTD device size and not > + * the MTD partition size because the maximum number of > + * bad blocks is a percentage of the whole device and > + * the bad blocks are not fairly disposed on a flash > + * device > + */ Would you please use proper kernel-style comments instead, to be consistent with the rest of the UBI code? I've amended this one, but wanted to note for future. I've re-based your patch against the latest UBI. I've also tried to improve the Kconfig help message as well. Below is the patch I ended up with. From cb14c6c5455443cbe960a36e77b3fcd0e5bc7152 Mon Sep 17 00:00:00 2001 From: Richard Genoud Date: Tue, 10 Jul 2012 18:23:41 +0200 Subject: [PATCH 2/2] UBI: use the whole MTD device size to get bad_peb_limit On NAND flash devices, UBI reserves some physical erase blocks (PEB) for bad block handling. Today, the number of reserved PEB can only be set as a percentage of the total number of PEB in each MTD partition. For example, for a NAND flash with 128KiB PEB, 2 MTD partition of 20MiB (mtd0) and 100MiB (mtd1) and 2% reserved PEB: - the UBI device on mtd0 will have 2 PEB reserved - the UBI device on mtd1 will have 16 PEB reserved The problem with this behaviour is that NAND flash manufacturers give a minimum number of valid block (NVB) during the endurance life of the device, e.g.: Parameter SymbolMinMaxUnit Notes -- Valid block number NVB 10041024 Blocks 1 Note: 1. Invalid blocks are block that contain one or more bad bits beyond ECC. The device may contain bad blocks upon shipment. Additional bad blocks may develop over time; however, the total number of available blocks will not drop below NVB during the endurance life of the device. From this number we can deduce the maximum number of bad PEB that a device will contain during its endurance life: a 128MiB NAND flash (1024 PEB) will not have less than 20 bad blocks during the flash endurance life. But the manufacturer doesn't tell where those bad block will appear. He doesn't say either if they will be equally disposed on the whole device (and I'm pretty sure they won't). So, according to the datasheets, we should reserve the maximum number of bad PEB for each UBI device (worst case scenario: 20 bad blocks appears on the smallest MTD partition). So this patch make UBI use the whole MTD device size to calculate the maximum bad expected eraseblocks. The Kconfig option is in per1024 blocks, thus it can have a default value of 20 which is *very* common for NAND devices. Signed-off-by: Richard Genoud Signed-off-by: Artem Bityutskiy --- drivers/mtd/ubi/Kconfig | 27 +-- drivers/mtd/ubi/build.c | 21 ++--- 2 files changed, 39 insertions(+), 9 deletions(-) diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig index b2f4f0f..98bda6c 100644 --- a/drivers/mtd/ubi/Kconfig +++ b/drivers/mtd/ubi/Kconfig @@ -28,14 +28,29 @@ config MTD_UBI_WL_THRESHOLD to 128 or 256, although it does not have to be power of 2). config MTD_UBI_BEB_LIMIT - int "Percentage of maximum expected bad eraseblocks" - default 2 - range 0 25 + int "Maximum expected bad eraseblock count per 1024 eraseblocks" + default 20 + range 2 256 help This option specifies the maximum bad physical eraseblocks UBI - expects on the UBI device (percents of total number of physical - eraseblocks on this MTD partition). If the underlying flash does not - admit of bad eraseblocks (e.g. NOR flash), this value is ignored. + expects on the MTD device (per 1024 eraseblocks). If the underlying + flash does not admit of bad eraseblocks (e.g. NOR flash), this value + is ignored. + + NAND datasheets often specify the minimum and maximum NVM (Number of + Valid Blocks) for the flashes' endurance lifetime. The maximum + expected bad eraseblocks per 1024 eraseblocks then can be calculated + as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs + (MaxNVB is basically the total count of eraseblocks on the chip). + + To put it differently, if this value is 20, UBI will try to reserve + about 1.9% of physical eraseblocks for bad blocks handling. And that + will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD + partition UBI attaches. This means that if you have, say, if a NAND + flash chip admits maximum 40 bad eraseblocks, and it is split on two + MTD partitions of the same size, UBI will reserve 40 eraseblocks when + attaching a partition. + Leave the default value if unsure. config
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
2012/8/15 Artem Bityutskiy : > On Tue, 2012-07-10 at 18:23 +0200, Richard Genoud wrote: >> + /* we are using here the whole MTD device size and not >> + * the MTD partition size because the maximum number of >> + * bad blocks is a percentage of the whole device and >> + * the bad blocks are not fairly disposed on a flash >> + * device >> + */ > > Would you please use proper kernel-style comments instead, to be > consistent with the rest of the UBI code? I've amended this one, but > wanted to note for future. ok, sorry for that. > > I've re-based your patch against the latest UBI. I've also tried to > improve the Kconfig help message as well. Below is the patch I ended up > with. > > > From cb14c6c5455443cbe960a36e77b3fcd0e5bc7152 Mon Sep 17 00:00:00 2001 > From: Richard Genoud > Date: Tue, 10 Jul 2012 18:23:41 +0200 > Subject: [PATCH 2/2] UBI: use the whole MTD device size to get bad_peb_limit > > On NAND flash devices, UBI reserves some physical erase blocks (PEB) for > bad block handling. Today, the number of reserved PEB can only be set as a > percentage of the total number of PEB in each MTD partition. For example, for > a > NAND flash with 128KiB PEB, 2 MTD partition of 20MiB (mtd0) and 100MiB (mtd1) > and 2% reserved PEB: > - the UBI device on mtd0 will have 2 PEB reserved > - the UBI device on mtd1 will have 16 PEB reserved > > The problem with this behaviour is that NAND flash manufacturers give a > minimum number of valid block (NVB) during the endurance life of the > device, e.g.: > > Parameter SymbolMinMaxUnit Notes > -- > Valid block number NVB 10041024 Blocks 1 > Note: > 1. Invalid blocks are block that contain one or more bad bits beyond > ECC. The device may contain bad blocks upon shipment. Additional bad > blocks may develop over time; however, the total number of available > blocks will not drop below NVB during the endurance life of the device. > > From this number we can deduce the maximum number of bad PEB that a device > will > contain during its endurance life: a 128MiB NAND flash (1024 PEB) will not > have > less than 20 bad blocks during the flash endurance life. > > But the manufacturer doesn't tell where those bad block will appear. He > doesn't > say either if they will be equally disposed on the whole device (and I'm > pretty > sure they won't). So, according to the datasheets, we should reserve the > maximum number of bad PEB for each UBI device (worst case scenario: 20 bad > blocks appears on the smallest MTD partition). > > So this patch make UBI use the whole MTD device size to calculate the maximum > bad expected eraseblocks. > > The Kconfig option is in per1024 blocks, thus it can have a default value of > 20 > which is *very* common for NAND devices. > > Signed-off-by: Richard Genoud > Signed-off-by: Artem Bityutskiy > --- > drivers/mtd/ubi/Kconfig | 27 +-- > drivers/mtd/ubi/build.c | 21 ++--- > 2 files changed, 39 insertions(+), 9 deletions(-) > > diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig > index b2f4f0f..98bda6c 100644 > --- a/drivers/mtd/ubi/Kconfig > +++ b/drivers/mtd/ubi/Kconfig > @@ -28,14 +28,29 @@ config MTD_UBI_WL_THRESHOLD > to 128 or 256, although it does not have to be power of 2). > > config MTD_UBI_BEB_LIMIT > - int "Percentage of maximum expected bad eraseblocks" > - default 2 > - range 0 25 > + int "Maximum expected bad eraseblock count per 1024 eraseblocks" > + default 20 > + range 2 256 > help > This option specifies the maximum bad physical eraseblocks UBI > - expects on the UBI device (percents of total number of physical > - eraseblocks on this MTD partition). If the underlying flash does not > - admit of bad eraseblocks (e.g. NOR flash), this value is ignored. > + expects on the MTD device (per 1024 eraseblocks). If the underlying > + flash does not admit of bad eraseblocks (e.g. NOR flash), this value > + is ignored. > + > + NAND datasheets often specify the minimum and maximum NVM (Number of > + Valid Blocks) for the flashes' endurance lifetime. The maximum > + expected bad eraseblocks per 1024 eraseblocks then can be calculated > + as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs > + (MaxNVB is basically the total count of eraseblocks on the chip). > + > + To put it differently, if this value is 20, UBI will try to reserve > + about 1.9% of physical eraseblocks for bad blocks handling. And that > + will be 1.9% of eraseblocks on the entire NAND chip, not just the > MTD > + partition UBI attaches. This means that if you have, say, if a NAND I
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
Hi Artem, Richard,
On Wed, 15 Aug 2012 18:08:51 +0300 Artem Bityutskiy wrote:
> 1. Invalid blocks are block that contain one or more bad bits beyond
> ECC.
I would remove this one sentence from the log, it is misleading; invalid
blocks are not necessarily related to ECC.
> if (CONFIG_MTD_UBI_BEB_LIMIT > 0) {
> - int percent = CONFIG_MTD_UBI_BEB_LIMIT;
> - int limit = mult_frac(ubi->peb_count, percent, 100);
> + int per1024 = CONFIG_MTD_UBI_BEB_LIMIT;
> + int limit, device_pebs;
> + uint64_t device_size;
> +
> + /*
> + * Here we are using size of the entire flash chip and
> + * not just the MTD partition size because the maximum
> + * number of bad eraseblocks is a percentage of the
> + * whole device and bad eraseblocks are not fairly
> + * distributed over the flash chip. So the worst case
> + * is that all the bad eraseblocks of the chip are in
> + * the MTD partition we are attaching (ubi->mtd).
> + */
> + device_size = mtd_get_device_size(ubi->mtd);
> + device_pebs = mtd_div_by_eb(device_size, ubi->mtd);
> + limit = mult_frac(device_pebs, per1024, 1024);
>
> /* Round it up */
> - if (mult_frac(limit, 100, percent) < ubi->peb_count)
> + if (mult_frac(limit, 1024, per1024) < ubi->peb_count)
Oops... should be:
+ if (mult_frac(limit, 1024, per1024) < device_pebs)
Regards,
Shmulik
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Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
Hi, One more thing... On Wed, 15 Aug 2012 18:08:51 +0300 Artem Bityutskiy wrote: > config MTD_UBI_BEB_LIMIT > - int "Percentage of maximum expected bad eraseblocks" > - default 2 > - range 0 25 > + int "Maximum expected bad eraseblock count per 1024 eraseblocks" > + default 20 > + range 2 256 Those defconfigs that explicilty set an original LIMIT should be adjusted as well, as the units have changed, no? Regards, Shmulik -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
2012/8/16 Shmulik Ladkani :
> Hi Artem, Richard,
>
> On Wed, 15 Aug 2012 18:08:51 +0300 Artem Bityutskiy
> wrote:
>> 1. Invalid blocks are block that contain one or more bad bits beyond
>> ECC.
>
> I would remove this one sentence from the log, it is misleading; invalid
> blocks are not necessarily related to ECC.
I agree (even if this sentence is from a nand datasheet !)
>
>> if (CONFIG_MTD_UBI_BEB_LIMIT > 0) {
>> - int percent = CONFIG_MTD_UBI_BEB_LIMIT;
>> - int limit = mult_frac(ubi->peb_count, percent, 100);
>> + int per1024 = CONFIG_MTD_UBI_BEB_LIMIT;
>> + int limit, device_pebs;
>> + uint64_t device_size;
>> +
>> + /*
>> + * Here we are using size of the entire flash chip and
>> + * not just the MTD partition size because the maximum
>> + * number of bad eraseblocks is a percentage of the
>> + * whole device and bad eraseblocks are not fairly
>> + * distributed over the flash chip. So the worst case
>> + * is that all the bad eraseblocks of the chip are in
>> + * the MTD partition we are attaching (ubi->mtd).
>> + */
>> + device_size = mtd_get_device_size(ubi->mtd);
>> + device_pebs = mtd_div_by_eb(device_size, ubi->mtd);
>> + limit = mult_frac(device_pebs, per1024, 1024);
>>
>> /* Round it up */
>> - if (mult_frac(limit, 100, percent) < ubi->peb_count)
>> + if (mult_frac(limit, 1024, per1024) < ubi->peb_count)
>
> Oops... should be:
>
> + if (mult_frac(limit, 1024, per1024) < device_pebs)
>
> Regards,
> Shmulik
Ok, I'll change that, may be in a separate patch, as it's a bug fix.
I'll add your signoff.
thanks !
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Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
On Thu, 2012-08-16 at 11:25 +0300, Shmulik Ladkani wrote: > I would remove this one sentence from the log, it is misleading; invalid > blocks are not necessarily related to ECC. Done. > + if (mult_frac(limit, 1024, per1024) < device_pebs) Done, thanks! -- Best Regards, Artem Bityutskiy signature.asc Description: This is a digitally signed message part
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
On Thu, 2012-08-16 at 12:35 +0200, Richard Genoud wrote: > Ok, I'll change that, may be in a separate patch, as it's a bug fix. Let me take care of this patch. I'll amend it myself, push to my tree and re-send to the mailing list for your review. Please, provide an updated version of the other patches instead. P.S. Of course, your authorship will be preserved. -- Best Regards, Artem Bityutskiy signature.asc Description: This is a digitally signed message part
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
On Thu, 2012-08-16 at 11:32 +0300, Shmulik Ladkani wrote: > > - default 2 > > - range 0 25 > > + int "Maximum expected bad eraseblock count per 1024 eraseblocks" > > + default 20 > > + range 2 256 > > Those defconfigs that explicilty set an original LIMIT should be > adjusted as well, as the units have changed, no? Yes, I'll do this, thanks! -- Best Regards, Artem Bityutskiy signature.asc Description: This is a digitally signed message part
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
On Thu, 2012-08-16 at 10:13 +0200, Richard Genoud wrote: > > + To put it differently, if this value is 20, UBI will try > to reserve > > + about 1.9% of physical eraseblocks for bad blocks > handling. And that > > + will be 1.9% of eraseblocks on the entire NAND chip, not > just the MTD > > + partition UBI attaches. This means that if you have, say, > if a NAND > I don't quite understand this sentence. > Maybe you meant: > This means that if you have, say, a NAND flash chip that admits a > maximum of 40 bad eraseblocks [...] > (but I'm not a native english speaker !) Fixed, thanks! -- Best Regards, Artem Bityutskiy signature.asc Description: This is a digitally signed message part
Re: [PATCH 3/4] UBI: use the whole MTD device size to get bad_peb_limit
2012/8/16 Shmulik Ladkani : > Hi, > > One more thing... > > On Wed, 15 Aug 2012 18:08:51 +0300 Artem Bityutskiy > wrote: >> config MTD_UBI_BEB_LIMIT >> - int "Percentage of maximum expected bad eraseblocks" >> - default 2 >> - range 0 25 >> + int "Maximum expected bad eraseblock count per 1024 eraseblocks" >> + default 20 >> + range 2 256 > > Those defconfigs that explicilty set an original LIMIT should be > adjusted as well, as the units have changed, no? you mean that it should be between 0 and 256 ? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
