mmc: core: Calculate the discard arg only once

In MMC, the discard arg is a read-only ext_csd parameter - set it once
on card init. To be consistent, do that for SD as well even though its
discard arg is always 0x0.

Signed-off-by: Avri Altman <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/core/block.c

···
 {
 	struct mmc_blk_data *md = mq->blkdata;
 	struct mmc_card *card = md->queue.card;
-	unsigned int from, nr, arg;
+	unsigned int from, nr;
 	int err = 0, type = MMC_BLK_DISCARD;
 	blk_status_t status = BLK_STS_OK;
 
···
 	from = blk_rq_pos(req);
 	nr = blk_rq_sectors(req);
 
-	if (mmc_can_discard(card))
-		arg = MMC_DISCARD_ARG;
-	else if (mmc_can_trim(card))
-		arg = MMC_TRIM_ARG;
-	else
-		arg = MMC_ERASE_ARG;
 	do {
 		err = 0;
 		if (card->quirks & MMC_QUIRK_INAND_CMD38) {
 			err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
 					 INAND_CMD38_ARG_EXT_CSD,
-					 arg == MMC_TRIM_ARG ?
+					 card->erase_arg == MMC_TRIM_ARG ?
 					 INAND_CMD38_ARG_TRIM :
 					 INAND_CMD38_ARG_ERASE,
 					 0);
 		}
 		if (!err)
-			err = mmc_erase(card, from, nr, arg);
+			err = mmc_erase(card, from, nr, card->erase_arg);
 	} while (err == -EIO && !mmc_blk_reset(md, card->host, type));
 	if (err)
 		status = BLK_STS_IOERR;

drivers/mmc/core/core.c

···
  * @card: card to erase
  * @from: first sector to erase
  * @nr: number of sectors to erase
- * @arg: erase command argument (SD supports only %MMC_ERASE_ARG)
+ * @arg: erase command argument (SD supports only %SD_ERASE_ARG)
  *
  * Caller must claim host before calling this function.
  */
···
 	if (!card->erase_size)
 		return -EOPNOTSUPP;
 
-	if (mmc_card_sd(card) && arg != MMC_ERASE_ARG)
+	if (mmc_card_sd(card) && arg != SD_ERASE_ARG)
 		return -EOPNOTSUPP;
 
 	if ((arg & MMC_SECURE_ARGS) &&

drivers/mmc/core/mmc.c

···
 			card->ext_csd.power_off_notification = EXT_CSD_POWER_ON;
 	}
 
+	/* set erase_arg */
+	if (mmc_can_discard(card))
+		card->erase_arg = MMC_DISCARD_ARG;
+	else if (mmc_can_trim(card))
+		card->erase_arg = MMC_TRIM_ARG;
+	else
+		card->erase_arg = MMC_ERASE_ARG;
+
 	/*
 	 * Select timing interface
 	 */

drivers/mmc/core/sd.c

···
 		}
 	}
 
+	card->erase_arg = SD_ERASE_ARG;
+
 	return 0;
 }
 

include/linux/mmc/card.h

···
  	unsigned int		erase_shift;	/* if erase unit is power 2 */
  	unsigned int		pref_erase;	/* in sectors */
 	unsigned int		eg_boundary;	/* don't cross erase-group boundaries */
+	unsigned int		erase_arg;	/* erase / trim / discard */
  	u8			erased_byte;	/* value of erased bytes */
 
 	u32			raw_cid[4];	/* raw card CID */

include/linux/mmc/sd.h

···
 #define SD_SWITCH_ACCESS_DEF	0
 #define SD_SWITCH_ACCESS_HS	1
 
+/*
+ * Erase/discard
+ */
+#define SD_ERASE_ARG			0x00000000
+
 #endif /* LINUX_MMC_SD_H */