Re: [PATCH v3 3/5] mmc: core: implement enhanced strobe support

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Hi,

On Tue, May 10, 2016 at 2:09 AM, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:
> Controllers use data strobe line to latch data from devices
> under hs400 mode, but not for cmd line. So since emmc 5.1, JEDEC
> introduces enhanced strobe mode for latching cmd response from
> emmc devices to host controllers. This new feature is optional,
> so it depends both on device's cap and host's cap to decide
> whether to use it or not.

I don't totally understand it, but two boards I'm working with have
eMMC devices that claim to be eMMC 5.0 devices but also have support
for strobe.  Did people just cherry-pick this feature from eMMC 5.1 to
their eMMC 5.0 devices?


> Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
> ---
>
> Changes in v3: None
> Changes in v2: None
>
>  drivers/mmc/core/bus.c   |  3 +-
>  drivers/mmc/core/core.c  |  8 +++++
>  drivers/mmc/core/mmc.c   | 79 ++++++++++++++++++++++++++++++++++++++++++++++--
>  include/linux/mmc/card.h |  1 +
>  include/linux/mmc/host.h | 11 +++++++
>  include/linux/mmc/mmc.h  |  3 ++
>  6 files changed, 102 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/core/bus.c b/drivers/mmc/core/bus.c
> index 4bc48f1..7e94b9d 100644
> --- a/drivers/mmc/core/bus.c
> +++ b/drivers/mmc/core/bus.c
> @@ -332,12 +332,13 @@ int mmc_add_card(struct mmc_card *card)
>                         mmc_card_ddr52(card) ? "DDR " : "",
>                         type);
>         } else {
> -               pr_info("%s: new %s%s%s%s%s card at address %04x\n",
> +               pr_info("%s: new %s%s%s%s%s%s card at address %04x\n",
>                         mmc_hostname(card->host),
>                         mmc_card_uhs(card) ? "ultra high speed " :
>                         (mmc_card_hs(card) ? "high speed " : ""),
>                         mmc_card_hs400(card) ? "HS400 " :
>                         (mmc_card_hs200(card) ? "HS200 " : ""),
> +                       mmc_card_hs400es(card) ? "Enhanced strobe" : "",

Nit: there should be a space before the quote.  Otherwise the message
runs together, like:

new HS400 Enhanced strobeMMC card at address 0001


>                         mmc_card_ddr52(card) ? "DDR " : "",
>                         uhs_bus_speed_mode, type, card->rca);
>         }
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 99275e4..a559501 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1127,6 +1127,14 @@ void mmc_set_initial_state(struct mmc_host *host)
>         host->ios.bus_width = MMC_BUS_WIDTH_1;
>         host->ios.timing = MMC_TIMING_LEGACY;
>         host->ios.drv_type = 0;
> +       host->ios.enhanced_strobe = false;
> +
> +       /*
> +        * Make sure we are in non-enhanced strobe mode before we
> +        * actually enable it in ext_csd.
> +        */
> +       if (host->ops->hs400_enhanced_strobe)
> +               host->ops->hs400_enhanced_strobe(host, &host->ios);
>
>         mmc_set_ios(host);
>  }
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index f99c47e..c2d1981 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -235,6 +235,11 @@ static void mmc_select_card_type(struct mmc_card *card)
>                 avail_type |= EXT_CSD_CARD_TYPE_HS400_1_2V;
>         }
>
> +       if ((caps2 & MMC_CAP2_HS400_ES) &&
> +           card->ext_csd.strobe_support &&
> +           (card_type & EXT_CSD_CARD_TYPE_HS400))
> +               avail_type |= EXT_CSD_CARD_TYPE_HS400ES;
> +
>         card->ext_csd.hs_max_dtr = hs_max_dtr;
>         card->ext_csd.hs200_max_dtr = hs200_max_dtr;
>         card->mmc_avail_type = avail_type;
> @@ -383,6 +388,7 @@ static int mmc_decode_ext_csd(struct mmc_card *card, u8 *ext_csd)
>                         mmc_card_set_blockaddr(card);
>         }
>
> +       card->ext_csd.strobe_support = ext_csd[EXT_CSD_STROBE_SUPPORT];
>         card->ext_csd.raw_card_type = ext_csd[EXT_CSD_CARD_TYPE];
>         mmc_select_card_type(card);
>
> @@ -1216,6 +1222,73 @@ out_err:
>         return err;
>  }
>
> +static int mmc_select_hs400es(struct mmc_card *card)
> +{
> +       struct mmc_host *host = card->host;
> +       int err = 0;
> +       u8 val;
> +
> +       err = mmc_select_bus_width(card);
> +       if (IS_ERR_VALUE(err))
> +               goto out_err;
> +
> +       /* Switch card to HS mode */
> +       err = mmc_select_hs(card);
> +       if (err) {
> +               pr_err("%s: switch to high-speed failed, err:%d\n",
> +                       mmc_hostname(host), err);
> +               goto out_err;
> +       }
> +
> +       err = mmc_switch_status(card);
> +       if (err)
> +               goto out_err;
> +
> +       /* Switch card to DDR with strobe bit */
> +       val = EXT_CSD_DDR_BUS_WIDTH_8 | EXT_CSD_BUS_WIDTH_STROBE;

In the hs400 function earlier in the file the check to confirm that
the bus width is 8 before doing this.  Should we do that here, too?

> +       err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> +                        EXT_CSD_BUS_WIDTH,
> +                        val,
> +                        card->ext_csd.generic_cmd6_time);
> +       if (err) {
> +               pr_err("%s: switch to bus width for hs400es failed, err:%d\n",
> +                       mmc_hostname(host), err);
> +               goto out_err;
> +       }
> +
> +       /* Switch card to HS400 */
> +       val = EXT_CSD_TIMING_HS400 |
> +             card->drive_strength << EXT_CSD_DRV_STR_SHIFT;
> +       err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> +                          EXT_CSD_HS_TIMING, val,
> +                          card->ext_csd.generic_cmd6_time,
> +                          true, false, true);
> +       if (err) {
> +               pr_err("%s: switch to hs400es failed, err:%d\n",
> +                       mmc_hostname(host), err);
> +               goto out_err;
> +       }
> +
> +       /* Set host controller to HS400 timing and frequency */
> +       mmc_set_timing(host, MMC_TIMING_MMC_HS400);
> +
> +       /* Controller enable enhanced strobe function */
> +       host->ios.enhanced_strobe = true;
> +       if (host->ops->hs400_enhanced_strobe)
> +               host->ops->hs400_enhanced_strobe(host, &host->ios);
> +
> +       err = mmc_switch_status(card);
> +       if (err)
> +               goto out_err;
> +
> +       return 0;
> +
> +out_err:
> +       pr_err("%s: %s failed, error %d\n", mmc_hostname(card->host),
> +              __func__, err);
> +       return err;
> +}
> +
>  static void mmc_select_driver_type(struct mmc_card *card)
>  {
>         int card_drv_type, drive_strength, drv_type;
> @@ -1297,7 +1370,7 @@ err:
>  }
>
>  /*
> - * Activate High Speed or HS200 mode if supported.
> + * Activate High Speed, HS200 or HS400ES mode if supported.
>   */
>  static int mmc_select_timing(struct mmc_card *card)
>  {
> @@ -1306,7 +1379,9 @@ static int mmc_select_timing(struct mmc_card *card)
>         if (!mmc_can_ext_csd(card))
>                 goto bus_speed;
>
> -       if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200)
> +       if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400ES)
> +               err = mmc_select_hs400es(card);
> +       else if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200)
>                 err = mmc_select_hs200(card);
>         else if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS)
>                 err = mmc_select_hs(card);
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index eb0151b..22defc2 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -95,6 +95,7 @@ struct mmc_ext_csd {
>         u8                      raw_partition_support;  /* 160 */
>         u8                      raw_rpmb_size_mult;     /* 168 */
>         u8                      raw_erased_mem_count;   /* 181 */
> +       u8                      strobe_support;         /* 184 */
>         u8                      raw_ext_csd_structure;  /* 194 */
>         u8                      raw_card_type;          /* 196 */
>         u8                      raw_driver_strength;    /* 197 */
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 2a06fb0..f98bd0e 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -19,6 +19,7 @@
>
>  #include <linux/mmc/core.h>
>  #include <linux/mmc/card.h>
> +#include <linux/mmc/mmc.h>
>  #include <linux/mmc/pm.h>
>
>  struct mmc_ios {
> @@ -77,6 +78,8 @@ struct mmc_ios {
>  #define MMC_SET_DRIVER_TYPE_A  1
>  #define MMC_SET_DRIVER_TYPE_C  2
>  #define MMC_SET_DRIVER_TYPE_D  3
> +
> +       bool enhanced_strobe;                   /* hs400es selection */
>  };
>
>  struct mmc_host_ops {
> @@ -143,6 +146,9 @@ struct mmc_host_ops {
>
>         /* Prepare HS400 target operating frequency depending host driver */
>         int     (*prepare_hs400_tuning)(struct mmc_host *host, struct mmc_ios *ios);
> +       /* Prepare enhanced strobe depending host driver */
> +       void    (*hs400_enhanced_strobe)(struct mmc_host *host,
> +                                        struct mmc_ios *ios);
>         int     (*select_drive_strength)(struct mmc_card *card,
>                                          unsigned int max_dtr, int host_drv,
>                                          int card_drv, int *drv_type);
> @@ -513,6 +519,11 @@ static inline bool mmc_card_hs400(struct mmc_card *card)
>         return card->host->ios.timing == MMC_TIMING_MMC_HS400;
>  }
>
> +static inline bool mmc_card_hs400es(struct mmc_card *card)
> +{
> +       return card->host->ios.enhanced_strobe == true;

nit: never need "== true".  Just:

  return card->host->ios.enhanced_strobe;

> +}
> +
>  void mmc_retune_timer_stop(struct mmc_host *host);
>
>  static inline void mmc_retune_needed(struct mmc_host *host)
> diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
> index 15f2c4a..c376209 100644
> --- a/include/linux/mmc/mmc.h
> +++ b/include/linux/mmc/mmc.h
> @@ -297,6 +297,7 @@ struct _mmc_csd {
>  #define EXT_CSD_PART_CONFIG            179     /* R/W */
>  #define EXT_CSD_ERASED_MEM_CONT                181     /* RO */
>  #define EXT_CSD_BUS_WIDTH              183     /* R/W */
> +#define EXT_CSD_STROBE_SUPPORT         184     /* RO */
>  #define EXT_CSD_HS_TIMING              185     /* R/W */
>  #define EXT_CSD_POWER_CLASS            187     /* R/W */
>  #define EXT_CSD_REV                    192     /* RO */
> @@ -380,12 +381,14 @@ struct _mmc_csd {
>  #define EXT_CSD_CARD_TYPE_HS400_1_2V   (1<<7)  /* Card can run at 200MHz DDR, 1.2V */
>  #define EXT_CSD_CARD_TYPE_HS400                (EXT_CSD_CARD_TYPE_HS400_1_8V | \
>                                          EXT_CSD_CARD_TYPE_HS400_1_2V)
> +#define EXT_CSD_CARD_TYPE_HS400ES      (1<<8)  /* Card can run at HS400ES */
>
>  #define EXT_CSD_BUS_WIDTH_1    0       /* Card is in 1 bit mode */
>  #define EXT_CSD_BUS_WIDTH_4    1       /* Card is in 4 bit mode */
>  #define EXT_CSD_BUS_WIDTH_8    2       /* Card is in 8 bit mode */
>  #define EXT_CSD_DDR_BUS_WIDTH_4        5       /* Card is in 4 bit DDR mode */
>  #define EXT_CSD_DDR_BUS_WIDTH_8        6       /* Card is in 8 bit DDR mode */
> +#define EXT_CSD_BUS_WIDTH_STROBE BIT(7)        /* Enhanced strobe mode */

nit: while your code should be OK, it seems better to be BIT(3), since
above is really:

0
BIT(0)
BIT(1)
BIT(2) | BIT(0)
BIT(2) | BIT(1)

...at least that's my understanding...
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