mmc: core: new discard feature support at eMMC v4.5

MMC v4.5 supports the DISCARD feature (CMD38).  It's different from
trim and there's no check bit.  Currently it's only supported at v4.5.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

5 files changed, 26 insertions, 1 deletions

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index e85816e1634a..370472797fff 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -756,7 +756,9 @@ static int mmc_blk_issue_discard_rq(struct mmc_queue *mq, struct request *req)
         from = blk_rq_pos(req);
         nr = blk_rq_sectors(req);
 
-        if (mmc_can_trim(card))
+        if (mmc_can_discard(card))
+                arg = MMC_DISCARD_ARG;
+        else if (mmc_can_trim(card))
                 arg = MMC_TRIM_ARG;
         else
                 arg = MMC_ERASE_ARG;
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index d9836e5a4e59..772de2cdfd1d 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1709,10 +1709,24 @@ int mmc_can_trim(struct mmc_card *card)
 {
         if (card->ext_csd.sec_feature_support & EXT_CSD_SEC_GB_CL_EN)
                 return 1;
+        if (mmc_can_discard(card))
+                return 1;
         return 0;
 }
 EXPORT_SYMBOL(mmc_can_trim);
 
+int mmc_can_discard(struct mmc_card *card)
+{
+        /*
+         * As there's no way to detect the discard support bit at v4.5
+         * use the s/w feature support filed.
+         */
+        if (card->ext_csd.feature_support & MMC_DISCARD_FEATURE)
+                return 1;
+        return 0;
+}
+EXPORT_SYMBOL(mmc_can_discard);
+
 int mmc_can_sanitize(struct mmc_card *card)
 {
         if (card->ext_csd.sec_feature_support & EXT_CSD_SEC_SANITIZE)
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index f8ea9387d75c..54088768776c 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -452,6 +452,10 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
                 card->ext_csd.rst_n_function = ext_csd[EXT_CSD_RST_N_FUNCTION];
         }
 
+        /* eMMC v4.5 or later */
+        if (card->ext_csd.rev >= 6)
+                card->ext_csd.feature_support |= MMC_DISCARD_FEATURE;
+
         card->ext_csd.raw_erased_mem_count = ext_csd[EXT_CSD_ERASED_MEM_CONT];
         if (ext_csd[EXT_CSD_ERASED_MEM_CONT])
                 card->erased_byte = 0xFF;
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index 711c3f8bfabd..551378508784 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -80,6 +80,9 @@ struct mmc_ext_csd {
         u8                      raw_sec_feature_support;/* 231 */
         u8                      raw_trim_mult;          /* 232 */
         u8                      raw_sectors[4];         /* 212 - 4 bytes */
+
+        unsigned int            feature_support;
+#define MMC_DISCARD_FEATURE     BIT(0)                  /* CMD38 feature */
 };
 
 struct sd_scr {
diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
index 9585835cbc42..e918120235bd 100644
--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h
@@ -146,6 +146,7 @@ extern int mmc_switch(struct mmc_card *, u8, u8, u8, unsigned int);
 #define MMC_ERASE_ARG           0x00000000
 #define MMC_SECURE_ERASE_ARG    0x80000000
 #define MMC_TRIM_ARG            0x00000001
+#define MMC_DISCARD_ARG         0x00000003
 #define MMC_SECURE_TRIM1_ARG    0x80000001
 #define MMC_SECURE_TRIM2_ARG    0x80008000
 
@@ -156,6 +157,7 @@ extern int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
                      unsigned int arg);
 extern int mmc_can_erase(struct mmc_card *card);
 extern int mmc_can_trim(struct mmc_card *card);
+extern int mmc_can_discard(struct mmc_card *card);
 extern int mmc_can_sanitize(struct mmc_card *card);
 extern int mmc_can_secure_erase_trim(struct mmc_card *card);
 extern int mmc_erase_group_aligned(struct mmc_card *card, unsigned int from,