On 4 June 2015 at 12:15, Yi Sun <yi.y.sun@xxxxxxxxx> wrote:
> Enhance Strobe is defined in v5.1 eMMC spec. This commit
> is to implement it.
Please elaborate in the change log.
I want to understand what this commit does, at least in a more
detailed summary and without having to read the eMMC spec. You may
also describe *why* we want this.
I have browsed through the code and seems okay, but I will make a more
detailed review once I get a better change log.
Kind regards
Uffe
>
> Signed-off-by: Yi Sun <yi.y.sun@xxxxxxxxx>
> ---
> drivers/mmc/core/mmc.c | 61 ++++++++++++++++++++++++++++++++++++++++++----
> include/linux/mmc/card.h | 1 +
> include/linux/mmc/mmc.h | 2 ++
> 3 files changed, 59 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index e519e31..c9ef2de 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -585,6 +585,12 @@ static int mmc_decode_ext_csd(struct mmc_card *card, u8 *ext_csd)
> card->ext_csd.ffu_capable =
> (ext_csd[EXT_CSD_SUPPORTED_MODE] & 0x1) &&
> !(ext_csd[EXT_CSD_FW_CONFIG] & 0x1);
> +
> + /* Enhance Strobe is supported since v5.1 which rev should be
> + * 8 but some eMMC devices can support it with rev 7. So handle
> + * Enhance Strobe here.
> + */
> + card->ext_csd.strobe_support = ext_csd[EXT_CSD_STROBE_SUPPORT];
> }
> out:
> return err;
> @@ -1049,9 +1055,28 @@ static int mmc_select_hs400(struct mmc_card *card)
> /*
> * HS400 mode requires 8-bit bus width
> */
> - if (!(card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400 &&
> - host->ios.bus_width == MMC_BUS_WIDTH_8))
> - return 0;
> + if (card->ext_csd.strobe_support) {
> + if (!(card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400 &&
> + host->caps & MMC_CAP_8_BIT_DATA))
> + return 0;
> +
> + /* For Enhance Strobe flow. For non Enhance Strobe, signal
> + * voltage will not be set.
> + */
> + if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200_1_2V)
> + err = __mmc_set_signal_voltage(host,
> + MMC_SIGNAL_VOLTAGE_120);
> +
> + if (err && card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200_1_8V)
> + err = __mmc_set_signal_voltage(host,
> + MMC_SIGNAL_VOLTAGE_180);
> + if (err)
> + return err;
> + } else {
> + if (!(card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400 &&
> + host->ios.bus_width == MMC_BUS_WIDTH_8))
> + return 0;
> + }
>
> /*
> * Before switching to dual data rate operation for HS400,
> @@ -1072,15 +1097,36 @@ static int mmc_select_hs400(struct mmc_card *card)
> return err;
> }
>
> + val = EXT_CSD_DDR_BUS_WIDTH_8;
> + if (card->ext_csd.strobe_support)
> + val |= EXT_CSD_BUS_WIDTH_STROBE;
> err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> EXT_CSD_BUS_WIDTH,
> - EXT_CSD_DDR_BUS_WIDTH_8,
> + val,
> card->ext_csd.generic_cmd6_time);
> if (err) {
> pr_err("%s: switch to bus width for hs400 failed, err:%d\n",
> mmc_hostname(host), err);
> return err;
> }
> + if (card->ext_csd.strobe_support) {
> + mmc_set_bus_width(host, MMC_BUS_WIDTH_8);
> + /*
> + * If controller can't handle bus width test,
> + * compare ext_csd previously read in 1 bit mode
> + * against ext_csd at new bus width
> + */
> + if (!(host->caps & MMC_CAP_BUS_WIDTH_TEST))
> + err = mmc_compare_ext_csds(card, MMC_BUS_WIDTH_8);
> + else
> + err = mmc_bus_test(card, MMC_BUS_WIDTH_8);
> +
> + if (err) {
> + pr_warn("%s: switch to bus width %d failed\n",
> + mmc_hostname(host), MMC_BUS_WIDTH_8);
> + return err;
> + }
> + }
>
> val = EXT_CSD_TIMING_HS400 |
> card->drive_strength << EXT_CSD_DRV_STR_SHIFT;
> @@ -1263,7 +1309,12 @@ 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)
> + /* For Enhance Strobe HS400 flow */
> + if (card->ext_csd.strobe_support &&
> + card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400 &&
> + card->host->caps & MMC_CAP_8_BIT_DATA)
> + err = mmc_select_hs400(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 4d3776d..b793b61 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/mmc.h b/include/linux/mmc/mmc.h
> index 15f2c4a..a1bb32c 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 */
> @@ -386,6 +387,7 @@ struct _mmc_csd {
> #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 0x80 /* Card is in 8 bit DDR mode */
>
> #define EXT_CSD_TIMING_BC 0 /* Backwards compatility */
> #define EXT_CSD_TIMING_HS 1 /* High speed */
> --
> 1.7.9.5
>
> --
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