Re: [PATCH v6 3/5] mmc: core: implement enhanced strobe support

Adrian Hunter
2016-05-26T11:08:53Z

On 26/05/16 04:56, Shawn Lin 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.
>
> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>

I have a couple of comments below, but they don't necessarily require any
action, so:

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

>
> Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
> Tested-by: Douglas Anderson <dianders@chromium.org>
> Tested-by: Jaehoon Chung <jh80.chung@samsung.com>
> ---
>
> Changes in v6:
> - add Doug's test-tag and Jaehoon's review-test-tag
>
> Changes in v5: None
> Changes in v4: None
> Changes in v3: None
> Changes in v2: None
>
> drivers/mmc/core/bus.c | 3 +-
> drivers/mmc/core/core.c | 9 ++++++
> drivers/mmc/core/mmc.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++--
> include/linux/mmc/card.h | 1 +
> include/linux/mmc/host.h | 11 +++++++
> include/linux/mmc/mmc.h | 3 ++
> 6 files changed, 108 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/core/bus.c b/drivers/mmc/core/bus.c
> index 4bc48f1..c64266f 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 " : "",
> 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..b0c1f07 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1127,6 +1127,15 @@ 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->caps2 & MMC_CAP2_HS400_ES) &&
> + 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..9dc91ba 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 &&
> + (avail_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 +1222,78 @@ out_err:
> return err;
> }
>
> +static int mmc_select_hs400es(struct mmc_card *card)
> +{
> + struct mmc_host *host = card->host;
> + int err = 0;
> + u8 val;
> +
> + if (!(host->caps & MMC_CAP_8_BIT_DATA)) {
> + err = -ENOTSUPP;
> + goto out_err;
> + }
> +
> + 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;

The spec. says "switch to High Speed mode and then set the clock frequency
to a value not greater than 52 MHz" which would tend to imply changing to
the High Speed frequency here. It shouldn't make any difference, so I don't
know if it is worth doing.

> +
> + /* Switch card to DDR with strobe bit */
> + val = EXT_CSD_DDR_BUS_WIDTH_8 | EXT_CSD_BUS_WIDTH_STROBE;
> + 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);
> +

And again here, if we followed the spec. exactly we would change to the
HS400 frequency here rather than after sending CMD13. Again, it shouldn't
make any difference, so I don't if it is worth doing.

> + 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 +1375,7 @@ 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 +1384,9 @@ 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..0eabb72 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;
> +}
> +
> 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 */
>
> #define EXT_CSD_TIMING_BC 0 /* Backwards compatility */
> #define EXT_CSD_TIMING_HS 1 /* High speed */
>