Re: [PATCH] mtd: rawnand: check nand support for cache reads

["Martin Hundebøll" <martin@geanix.com>]

On Fri, 2023-09-22 at 12:01 +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 implements 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 no 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")
> 
> Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
> ---
> @Martin, Måns:
> I would appreciate if you could test this on your hardware.
> 
> @Miguel:
> I didn't have the time to test this on ONFI/JEDEC devices with
> support
> yet, I'd be fine if you hold off merging this.
> 
>  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       | 1 +
>  6 files changed, 14 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..e6ecbc4b2493 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;

Missing ` = true` here ?

> +
>         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..bf79bf2b5866 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;

And here?

// Martin
> +
>         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..766856fcaba8 100644
> --- a/include/linux/mtd/rawnand.h
> +++ b/include/linux/mtd/rawnand.h
> @@ -233,6 +233,7 @@ 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);
>