[PATCH v6 4/5] mmc: block: Support alternative_gpt_sector() operation

[Dmitry Osipenko <digetx@gmail.com>]

Support generic alternative_gpt_sector() block device operation which
calculates custom GPT location. Add new MMC_CAP2_ALTERNATIVE_GPT_SECTOR
flag that enables scanning of the alternative sector.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/mmc/core/block.c | 21 +++++++++++++++++++++
 drivers/mmc/core/core.c  | 35 +++++++++++++++++++++++++++++++++++
 drivers/mmc/core/core.h  |  2 ++
 include/linux/mmc/host.h |  1 +
 4 files changed, 59 insertions(+)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 672cc505ce37..edd26164be06 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -801,6 +801,26 @@ static int mmc_blk_compat_ioctl(struct block_device *bdev, fmode_t mode,
 }
 #endif
 
+static int mmc_blk_alternative_gpt_sector(struct gendisk *disk,
+					  sector_t *sector)
+{
+	struct mmc_blk_data *md;
+	int ret;
+
+	md = mmc_blk_get(disk);
+	if (!md)
+		return -EINVAL;
+
+	if (md->queue.card)
+		ret = mmc_card_alternative_gpt_sector(md->queue.card, sector);
+	else
+		ret = -ENODEV;
+
+	mmc_blk_put(md);
+
+	return ret;
+}
+
 static const struct block_device_operations mmc_bdops = {
 	.open			= mmc_blk_open,
 	.release		= mmc_blk_release,
@@ -810,6 +830,7 @@ static const struct block_device_operations mmc_bdops = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl		= mmc_blk_compat_ioctl,
 #endif
+	.alternative_gpt_sector	= mmc_blk_alternative_gpt_sector,
 };
 
 static int mmc_blk_part_switch_pre(struct mmc_card *card,
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 6249c83d616f..c5cdd56051cb 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2150,6 +2150,41 @@ int mmc_detect_card_removed(struct mmc_host *host)
 }
 EXPORT_SYMBOL(mmc_detect_card_removed);
 
+int mmc_card_alternative_gpt_sector(struct mmc_card *card, sector_t *gpt_sector)
+{
+	unsigned int boot_sectors_num;
+
+	if ((!(card->host->caps2 & MMC_CAP2_ALT_GPT_SECTOR)))
+		return -EOPNOTSUPP;
+
+	/* filter out unrelated cards */
+	if (card->ext_csd.rev < 3 ||
+	    !mmc_card_mmc(card) ||
+	    !mmc_card_is_blockaddr(card) ||
+	     mmc_card_is_removable(card->host))
+		return -ENOENT;
+
+	/*
+	 * eMMC storage has two special boot partitions in addition to the
+	 * main one.  NVIDIA's bootloader linearizes eMMC boot0->boot1->main
+	 * accesses, this means that the partition table addresses are shifted
+	 * by the size of boot partitions.  In accordance with the eMMC
+	 * specification, the boot partition size is calculated as follows:
+	 *
+	 *	boot partition size = 128K byte x BOOT_SIZE_MULT
+	 *
+	 * Calculate number of sectors occupied by the both boot partitions.
+	 */
+	boot_sectors_num = card->ext_csd.raw_boot_mult * SZ_128K /
+			   SZ_512 * MMC_NUM_BOOT_PARTITION;
+
+	/* Defined by NVIDIA and used by Android devices. */
+	*gpt_sector = card->ext_csd.sectors - boot_sectors_num - 1;
+
+	return 0;
+}
+EXPORT_SYMBOL(mmc_card_alternative_gpt_sector);
+
 void mmc_rescan(struct work_struct *work)
 {
 	struct mmc_host *host =
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index 0c4de2030b3f..7931a4f0137d 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -119,6 +119,8 @@ void mmc_release_host(struct mmc_host *host);
 void mmc_get_card(struct mmc_card *card, struct mmc_ctx *ctx);
 void mmc_put_card(struct mmc_card *card, struct mmc_ctx *ctx);
 
+int mmc_card_alternative_gpt_sector(struct mmc_card *card, sector_t *sector);
+
 /**
  *	mmc_claim_host - exclusively claim a host
  *	@host: mmc host to claim
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 0abd47e9ef9b..73a4cc063bb0 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -398,6 +398,7 @@ struct mmc_host {
 #else
 #define MMC_CAP2_CRYPTO		0
 #endif
+#define MMC_CAP2_ALT_GPT_SECTOR	(1 << 28)	/* Host with eMMC card that has GPT entry at a non-standard location */
 
 	int			fixed_drv_type;	/* fixed driver type for non-removable media */
 
-- 
2.32.0