[PATCH v2] mmc: enable Enhance Strobe for HS400.

[Yi Sun <yi.y.sun@intel.com>]

Enhance Strobe is defined in v5.1 eMMC spec. This commit
is to implement it.

Normal Strobe signal for HS400 is only provided during
Data Out and CRC Response. While Enhance Strobe is enabled,
Strobe signal is provided during Data Out, CRC Response and
CMD Response.

While enabling Enhance Strobe, the initialization of HS400
does not need enabling HS200 and executing tuning anymore.
This simplifies the HS400 initialization process much.

Per spec, there is a STROBE_SUPPORT added in EXT_CSD register
to indicate that card supports Enhance Strobe or not. If it is
supported, host can enable this feature by enabling the most
significant bit of BUS_WIDTH before set HS_TIMING to HS400.

Signed-off-by: Yi Sun <yi.y.sun@intel.com>
---
 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