Re: [PATCH v2] mtd: rawnand: Ensure the nand chip supports cached reads

Miquel Raynal
2023-09-25T15:19:20Z

Hi Martin,

+ Bean and Domenico

martin@geanix.com wrote on Mon, 25 Sep 2023 13:01:06 +0200:

> Hi Rouven,
>
> On Fri, 2023-09-22 at 16:17 +0200, Rouven Czerwinski wrote:
> > Both the JEDEC and ONFI specification say that read cache sequential
> > support is an optional command. This means that we not only need to
> > check whether the individual controller supports the command, we also
> > need to check the parameter pages for both ONFI and JEDEC NAND
> > flashes
> > before enabling sequential cache reads.
> >
> > This fixes support for NAND flashes which don't support enabling
> > cache
> > reads, i.e. Samsung K9F4G08U0F or Toshiba TC58NVG0S3HTA00.
> >
> > Sequential cache reads are now only available for ONFI and JEDEC
> > devices, if individual vendors implement this, it needs to be enabled
> > per vendor.
> >
> > Tested on i.MX6Q with a Samsung NAND flash chip that doesn't support
> > sequential reads.
> >
> > Fixes: 003fe4b9545b ("mtd: rawnand: Support for sequential cache
> > reads")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
>
> Thanks for this. It works as expected for my Toshiba chip, obviously
> because it doesn't use ONFI or JEDEC.
>
> Unfortunately, my Micron chip does use ONFI, and it sets the cached-
> read-supported bit. It then fails when reading afterwords:
>
> kernel: ONFI_OPT_CMD_READ_CACHE # debug added by me
> kernel: nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xdc
> kernel: nand: Micron MT29F4G08ABAFAWP
> kernel: nand: 512 MiB, SLC, erase size: 256 KiB, page size: 4096, OOB
> size: 256
> kernel: nand: continued read supported # debug added by me
> kernel: Bad block table found at page 131008, version 0x01
> kernel: Bad block table found at page 130944, version 0x01
> kernel: 2 fixed-partitions partitions found on MTD device gpmi-nand
> kernel: Creating 2 MTD partitions on "gpmi-nand":
> kernel: 0x000000000000-0x000000800000 : "boot"
> kernel: 0x000000800000-0x000020000000 : "ubi"
> kernel: gpmi-nand 1806000.nand-controller: driver registered.
>
> ...
>
> kernel: ubi0: default fastmap pool size: 100
> kernel: ubi0: default fastmap WL pool size: 50
> kernel: ubi0: attaching mtd1
> kernel: ubi0: scanning is finished
> kernel: ubi0: attached mtd1 (name "ubi", size 504 MiB)
> kernel: ubi0: PEB size: 262144 bytes (256 KiB), LEB size: 253952 bytes
> kernel: ubi0: min./max. I/O unit sizes: 4096/4096, sub-page size 4096
> kernel: ubi0: VID header offset: 4096 (aligned 4096), data offset: 8192
> kernel: ubi0: good PEBs: 2012, bad PEBs: 4, corrupted PEBs: 0
> kernel: ubi0: user volume: 9, internal volumes: 1, max. volumes count:
> 128
> kernel: ubi0: max/mean erase counter: 4/2, WL threshold: 4096, image
> sequence number: 1431497221
> kernel: ubi0: available PEBs: 12, total reserved PEBs: 2000, PEBs
> reserved for bad PEB handling: 36
> kernel: block ubiblock0_4: created from ubi0:4(rootfs.a)
> kernel: ubi0: background thread "ubi_bgt0d" started, PID 36
> kernel: block ubiblock0_6: created from ubi0:6(appfs.a)
> kernel: block ubiblock0_7: created from ubi0:7(appfs.b)
>
> ...
>
> kernel: SQUASHFS error: Unable to read directory block [4b6d15c:ed1]
> kernel: SQUASHFS error: Unable to read directory block [4b6f15e:125]
> kernel: SQUASHFS error: Unable to read directory block [4b6d15c:1dae]
> kernel: SQUASHFS error: Unable to read directory block [4b6d15c:ed1]
> (d-sysctl)[55]: systemd-sysctl.service: Failed to set up credentials:
> Protocol error
> kernel: SQUASHFS error: Unable to read directory block [4b73162:14f0]
> kernel: SQUASHFS error: Unable to read directory block [4b6f15e:838]
> systemd[1]: Starting Create Static Device Nodes in /dev...
> kernel: SQUASHFS error: Unable to read directory block [4b6d15c:ed1]
> kernel: SQUASHFS error: Unable to read directory block [4b6d15c:ed1]
> kernel: SQUASHFS error: Unable to read directory block [4b6f15e:838]
> kernel: SQUASHFS error: Unable to read directory block [4b6d15c:1dae]
> kernel: SQUASHFS error: Unable to read directory block [4b6f15e:125]
>
> I've briefly tried adding some error info the the squashfs error
> messages, but it looks like it's getting bad data. I.e. one failure a
> sanity check of `dir_count`:
>
> if (dir_count > SQUASHFS_DIR_COUNT)
> goto data_error;
>
> It fails with `dir_count` being 1952803684 ...
>
> So is this a case of wrong/bad timings?
>
> Miquel:
> I can tell from the code, that the READCACHESEQ operations are followed
> by NAND_OP_WAIT_RDY(tR_max, tRR_min). From the Micron datasheet[0], it
> should be NAND_OP_WAIT_RDY(tRCBSY_max, tRR_min), where tRCBSY is
> defined to be between 3 and 25 µs.
>
> Not sure if this is related though.

I believe tR_max is bigger (200us), but please check that this is
actually the case, you can also try enlarging this delay. But if it was
a timeout issue we would probably see errors from the controller driver?

Bean, Domenico, is there any AN or specific document which I missed
asking not to use this feature on specific chips? Are they supposed to
work?

>
> [0] (login required)
> https://www.micron.com/products/nand-flash/slc-nand/part-catalog/mt29f4g08abadawp
>
> // Martin
>
> > ---
> > v2:
> > - change title as suggested by Miquel
> > - adjust controller sentence from implement to support
> > - fix missing true assignement for flashes
> > - add CC stable instead of empty line
> > - add documentation comment for new supports_read_cache bool inside
> >   nand parameter struct
> >
> >  drivers/mtd/nand/raw/nand_base.c  | 3 +++
> >  drivers/mtd/nand/raw/nand_jedec.c | 3 +++
> >  drivers/mtd/nand/raw/nand_onfi.c  | 3 +++
> >  include/linux/mtd/jedec.h         | 3 +++
> >  include/linux/mtd/onfi.h          | 1 +
> >  include/linux/mtd/rawnand.h       | 2 ++
> >  6 files changed, 15 insertions(+)
> >
> > diff --git a/drivers/mtd/nand/raw/nand_base.c
> > b/drivers/mtd/nand/raw/nand_base.c
> > index d4b55155aeae..1fcac403cee6 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -5110,6 +5110,9 @@ static void
> > rawnand_check_cont_read_support(struct nand_chip *chip)
> >  {
> >         struct mtd_info *mtd = nand_to_mtd(chip);
> >
> > +       if (!chip->parameters.supports_read_cache)
> > +               return;
> > +
> >         if (chip->read_retries)
> >                 return;
> >
> > diff --git a/drivers/mtd/nand/raw/nand_jedec.c
> > b/drivers/mtd/nand/raw/nand_jedec.c
> > index 836757717660..b3cc8f360529 100644
> > --- a/drivers/mtd/nand/raw/nand_jedec.c
> > +++ b/drivers/mtd/nand/raw/nand_jedec.c
> > @@ -94,6 +94,9 @@ int nand_jedec_detect(struct nand_chip *chip)
> >                 goto free_jedec_param_page;
> >         }
> >
> > +       if (p->opt_cmd[0] & JEDEC_OPT_CMD_READ_CACHE)
> > +               chip->parameters.supports_read_cache = true;
> > +
> >         memorg->pagesize = le32_to_cpu(p->byte_per_page);
> >         mtd->writesize = memorg->pagesize;
> >
> > diff --git a/drivers/mtd/nand/raw/nand_onfi.c
> > b/drivers/mtd/nand/raw/nand_onfi.c
> > index f15ef90aec8c..861975e44b55 100644
> > --- a/drivers/mtd/nand/raw/nand_onfi.c
> > +++ b/drivers/mtd/nand/raw/nand_onfi.c
> > @@ -303,6 +303,9 @@ int nand_onfi_detect(struct nand_chip *chip)
> >                            ONFI_FEATURE_ADDR_TIMING_MODE, 1);
> >         }
> >
> > +       if (le16_to_cpu(p->opt_cmd) & ONFI_OPT_CMD_READ_CACHE)
> > +               chip->parameters.supports_read_cache = true;
> > +
> >         onfi = kzalloc(sizeof(*onfi), GFP_KERNEL);
> >         if (!onfi) {
> >                 ret = -ENOMEM;
> > diff --git a/include/linux/mtd/jedec.h b/include/linux/mtd/jedec.h
> > index 0b6b59f7cfbd..56047a4e54c9 100644
> > --- a/include/linux/mtd/jedec.h
> > +++ b/include/linux/mtd/jedec.h
> > @@ -21,6 +21,9 @@ struct jedec_ecc_info {
> >  /* JEDEC features */
> >  #define JEDEC_FEATURE_16_BIT_BUS       (1 << 0)
> >
> > +/* JEDEC Optional Commands */
> > +#define JEDEC_OPT_CMD_READ_CACHE       BIT(1)
> > +
> >  struct nand_jedec_params {
> >         /* rev info and features block */
> >         /* 'J' 'E' 'S' 'D'  */
> > diff --git a/include/linux/mtd/onfi.h b/include/linux/mtd/onfi.h
> > index a7376f9beddf..55ab2e4d62f9 100644
> > --- a/include/linux/mtd/onfi.h
> > +++ b/include/linux/mtd/onfi.h
> > @@ -55,6 +55,7 @@
> >  #define ONFI_SUBFEATURE_PARAM_LEN      4
> >
> >  /* ONFI optional commands SET/GET FEATURES supported? */
> > +#define ONFI_OPT_CMD_READ_CACHE                BIT(1)
> >  #define ONFI_OPT_CMD_SET_GET_FEATURES  BIT(2)
> >
> >  struct nand_onfi_params {
> > diff --git a/include/linux/mtd/rawnand.h
> > b/include/linux/mtd/rawnand.h
> > index 90a141ba2a5a..c29ace15a053 100644
> > --- a/include/linux/mtd/rawnand.h
> > +++ b/include/linux/mtd/rawnand.h
> > @@ -225,6 +225,7 @@ struct gpio_desc;
> >   * struct nand_parameters - NAND generic parameters from the
> > parameter page
> >   * @model: Model name
> >   * @supports_set_get_features: The NAND chip supports
> > setting/getting features
> > + * @supports_read_cache: The NAND chip supports read cache
> > operations
> >   * @set_feature_list: Bitmap of features that can be set
> >   * @get_feature_list: Bitmap of features that can be get
> >   * @onfi: ONFI specific parameters
> > @@ -233,6 +234,7 @@ struct nand_parameters {
> >         /* Generic parameters */
> >         const char *model;
> >         bool supports_set_get_features;
> > +       bool supports_read_cache;
> >         DECLARE_BITMAP(set_feature_list, ONFI_FEATURE_NUMBER);
> >         DECLARE_BITMAP(get_feature_list, ONFI_FEATURE_NUMBER);
> >
> >
> > base-commit: 42dc814987c1feb6410904e58cfd4c36c4146150
>

Thanks,
Miquèl