Re: [PATCH v2 3/3] mmc: core: Add discard support to sd

[Ulf Hansson]

On Wed, 6 Feb 2019 at 12:29, Avri Altman <avri.altman@xxxxxxx> wrote:
>
> SD spec v5.1 adds discard support. The flows and commands are similar to
> mmc, so just set the discard arg in CMD38.
>
> Actually, there is no need to check for the spec version like we are
> doing, as it is assured that the reserved bits in earlier versions are
> null. Do that anyway to document the spec version that introduce it.
>
> Signed-off-by: Avri Altman <avri.altman@xxxxxxx>

Deferring this a bit, need some more time to review.

Kind regards
Uffe


> ---
>  drivers/mmc/core/core.c |  6 +++++-
>  drivers/mmc/core/sd.c   | 10 +++++++++-
>  include/linux/mmc/sd.h  |  1 +
>  3 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index de0f1a1..4d62f28 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2164,7 +2164,7 @@ static unsigned int mmc_align_erase_size(struct mmc_card *card,
>   * @card: card to erase
>   * @from: first sector to erase
>   * @nr: number of sectors to erase
> - * @arg: erase command argument (SD supports only %SD_ERASE_ARG)
> + * @arg: erase command argument
>   *
>   * Caller must claim host before calling this function.
>   */
> @@ -2181,6 +2181,9 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>         if (!card->erase_size)
>                 return -EOPNOTSUPP;
>
> +       if (mmc_card_sd(card) && arg == SD_DISCARD_ARG)
> +               goto skip_arg_testing;
> +
>         if (mmc_card_sd(card) && arg != SD_ERASE_ARG)
>                 return -EOPNOTSUPP;
>
> @@ -2200,6 +2203,7 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>         if (arg == MMC_ERASE_ARG)
>                 nr = mmc_align_erase_size(card, &from, &to, nr);
>
> +skip_arg_testing:
>         if (nr == 0)
>                 return 0;
>
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index c2db94d..2b4fc22 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -231,6 +231,8 @@ static int mmc_read_ssr(struct mmc_card *card)
>  {
>         unsigned int au, es, et, eo;
>         __be32 *raw_ssr;
> +       u32 resp[4] = {};
> +       u8 discard_support;
>         int i;
>
>         if (!(card->csd.cmdclass & CCC_APP_SPEC)) {
> @@ -276,7 +278,13 @@ static int mmc_read_ssr(struct mmc_card *card)
>                 }
>         }
>
> -       card->erase_arg = SD_ERASE_ARG;
> +       /*
> +        * starting SD5.1 discard is supported if DISCARD_SUPPORT (b313) is set
> +        */
> +       resp[3] = card->raw_ssr[6];
> +       discard_support = UNSTUFF_BITS(resp, 313 - 288, 1);
> +       card->erase_arg = (card->scr.sda_specx && discard_support) ?
> +                           SD_DISCARD_ARG : SD_ERASE_ARG;
>
>         return 0;
>  }
> diff --git a/include/linux/mmc/sd.h b/include/linux/mmc/sd.h
> index 1a6d10f..ec94a5a 100644
> --- a/include/linux/mmc/sd.h
> +++ b/include/linux/mmc/sd.h
> @@ -95,5 +95,6 @@
>   * Erase/discard
>   */
>  #define SD_ERASE_ARG                   0x00000000
> +#define SD_DISCARD_ARG                 0x00000001
>
>  #endif /* LINUX_MMC_SD_H */
> --
> 1.9.1
>