mmc: Add CONFIG_EMBEDDED_MMC_START_OFFSET configuration

enables platforms to specify a non-zero offset for the MBR and kernel-visible
file systems, for embedded systems which store proprietary data at the start
of the eMMC device.

Change-Id: Id58abaffddda7d7aeded8573f4aba6cc0c903a24

6 files changed, 65 insertions, 1 deletions

diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig
index f2eeb38efa65..1f8494e86d34 100644
--- a/drivers/mmc/Kconfig
+++ b/drivers/mmc/Kconfig
@@ -12,6 +12,18 @@ menuconfig MMC
 	  If you want MMC/SD/SDIO support, you should say Y here and
 	  also to your specific host controller driver.
 
+config EMBEDDED_MMC_START_OFFSET
+	bool "MMC start sector offset"
+	depends on MMC != n
+	help
+	  This enables a per-controller fixed offset in sectors / bytes to
+	  the location of the master boot record in the device, and reduces
+	  the capacity of the device by a corresponding amount.  This is
+	  primarily used by embedded systems with embedded MMC storage where
+	  the initial sectors are used by boot firmware.  If you do not know
+	  if this applies to your system, say N here.
+
+
 config MMC_DEBUG
 	bool "MMC debugging"
 	depends on MMC != n
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 32af45c419f4..2ad71ba187df 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -141,6 +141,10 @@ static int mmc_decode_csd(struct mmc_card *card)
 	e = UNSTUFF_BITS(resp, 47, 3);
 	m = UNSTUFF_BITS(resp, 62, 12);
 	csd->capacity	  = (1 + m) << (e + 2);
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+	/* for sector-addressed cards, this will cause csd->capacity to wrap */
+	csd->capacity -= card->host->ops->get_host_offset(card->host);
+#endif
 
 	csd->read_blkbits = UNSTUFF_BITS(resp, 80, 4);
 	csd->read_partial = UNSTUFF_BITS(resp, 79, 1);
@@ -221,8 +225,17 @@ static int mmc_read_ext_csd(struct mmc_card *card)
 			ext_csd[EXT_CSD_SEC_CNT + 1] << 8 |
 			ext_csd[EXT_CSD_SEC_CNT + 2] << 16 |
 			ext_csd[EXT_CSD_SEC_CNT + 3] << 24;
-		if (card->ext_csd.sectors)
+		if (card->ext_csd.sectors) {
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+			unsigned offs;
+			offs = card->host->ops->get_host_offset(card->host);
+			offs >>= 9;
+			BUG_ON(offs >= card->ext_csd.sectors);
+			card->ext_csd.sectors -= offs;
+#endif
 			mmc_card_set_blockaddr(card);
+		}
+
 	}
 
 	switch (ext_csd[EXT_CSD_CARD_TYPE]) {
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 8fe5e9ece251..79c3c32b6f1c 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -110,6 +110,11 @@ static int mmc_decode_csd(struct mmc_card *card)
 		e = UNSTUFF_BITS(resp, 47, 3);
 		m = UNSTUFF_BITS(resp, 62, 12);
 		csd->capacity	  = (1 + m) << (e + 2);
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+		BUG_ON(card->host->ops->get_host_offset(card->host) >=
+			csd->capacity);
+		csd->capacity -= card->host->ops->get_host_offset(card->host);
+#endif
 
 		csd->read_blkbits = UNSTUFF_BITS(resp, 80, 4);
 		csd->read_partial = UNSTUFF_BITS(resp, 79, 1);
@@ -138,6 +143,12 @@ static int mmc_decode_csd(struct mmc_card *card)
 
 		m = UNSTUFF_BITS(resp, 48, 22);
 		csd->capacity     = (1 + m) << 10;
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+		BUG_ON((card->host->ops->get_host_offset(card->host) >> 9) >=
+			csd->capacity);
+		csd->capacity -=
+			(card->host->ops->get_host_offset(card->host) >> 9);
+#endif
 
 		csd->read_blkbits = 9;
 		csd->read_partial = 0;
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index c279fbc4c2e5..2d47bf53a88c 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -900,7 +900,17 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
 
 	sdhci_prepare_data(host, cmd->data);
 
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+	if (cmd->data) {
+		/* It is assumed that the device is block addressed. */
+		sdhci_writel(host, cmd->arg + (host->start_offset >> 9),
+			SDHCI_ARGUMENT);
+	} else {
+		sdhci_writel(host, cmd->arg, SDHCI_ARGUMENT);
+	}
+#else
 	sdhci_writel(host, cmd->arg, SDHCI_ARGUMENT);
+#endif
 
 	sdhci_set_transfer_mode(host, cmd->data);
 
@@ -1216,11 +1226,22 @@ out:
 	spin_unlock_irqrestore(&host->lock, flags);
 }
 
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+static unsigned int sdhci_get_host_offset(struct mmc_host *mmc) {
+	struct sdhci_host *host;
+	host = mmc_priv(mmc);
+	return host->start_offset;
+}
+#endif
+
 static const struct mmc_host_ops sdhci_ops = {
 	.request	= sdhci_request,
 	.set_ios	= sdhci_set_ios,
 	.get_ro		= sdhci_get_ro,
 	.enable_sdio_irq = sdhci_enable_sdio_irq,
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+	.get_host_offset = sdhci_get_host_offset,
+#endif
 };
 
 /*****************************************************************************\
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index ce5f1d73dc04..98aa621fd22b 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -286,6 +286,10 @@ struct sdhci_host {
 
 	struct timer_list	timer;		/* Timer for timeouts */
 
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+	unsigned int		start_offset;	/* Zero-offset for MBR */
+#endif
+
 	unsigned long		private[0] ____cacheline_aligned;
 };
 
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index c3b88ff5654f..31450dc27a43 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -107,6 +107,9 @@ struct mmc_host_ops {
 	int	(*get_cd)(struct mmc_host *host);
 
 	void	(*enable_sdio_irq)(struct mmc_host *host, int enable);
+#ifdef CONFIG_EMBEDDED_MMC_START_OFFSET
+	unsigned int (*get_host_offset)(struct mmc_host *host);
+#endif
 };
 
 struct mmc_card;