[RFC 1/2] drivers: mmc: write protect active boot area after mmc init.

[Ying-Chun Liu]

From: "Ying-Chun Liu (PaulLiu)" <paul.liu at linaro.org>

This commit implements write protection for active boot partition for
eMMC. The active boot partition is write protected, and it is still
able to write to the inactive boot partition.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu at linaro.org>
Cc: Peng Fan <peng.fan at nxp.com>
Cc: Jaehoon Chung <jh80.chung at samsung.com>
---
 drivers/mmc/Kconfig | 10 ++++++++
 drivers/mmc/mmc.c   | 58 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig
index e0927ce1c9..c4bae743e6 100644
--- a/drivers/mmc/Kconfig
+++ b/drivers/mmc/Kconfig
@@ -100,6 +100,16 @@ config MMC_HW_PARTITIONING
 	  This adds a command and an API to do hardware partitioning on eMMC
 	  devices.
 
+config MMC_WRITE_PROTECT_ACTIVE_BOOT
+	bool "Write protection for active boot partition (eMMC)"
+	depends on MMC_HW_PARTITIONING
+	default n
+	help
+	  Write protection for active boot partition when mmc initialized.
+	  This option protects the active boot partition so that it cannot
+	  be written. But it is still able to write to the inactive boot
+	  partition.
+
 config SUPPORT_EMMC_RPMB
 	bool "Support eMMC replay protected memory block (RPMB)"
 	imply CMD_MMC_RPMB
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 4d9871d69f..8620918749 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -860,6 +860,60 @@ int mmc_boot_wp(struct mmc *mmc)
 	return mmc_switch(mmc, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_BOOT_WP, 1);
 }
 
+/**
+ * mmc_boot_wp_single_partition() - set write protection to a boot partition.
+ *
+ * This function sets a single boot partition to protect and leave the
+ * other partition writable.
+ *
+ * @param mmc the mmc device.
+ * @param partition 0 - first boot partition, 1 - second boot partition.
+ */
+int mmc_boot_wp_single_partition(struct mmc *mmc, int partition)
+{
+	u8 value;
+	int ret;
+
+	value = 1;
+
+	if (partition == 0) {
+		value |= 0x80;
+		ret = mmc_switch(mmc,
+				 EXT_CSD_CMD_SET_NORMAL,
+				 EXT_CSD_BOOT_WP,
+				 value);
+	} else if (partition == 1) {
+		value |= 0x80;
+		value |= 0x02;
+		ret = mmc_switch(mmc,
+				 EXT_CSD_CMD_SET_NORMAL,
+				 EXT_CSD_BOOT_WP,
+				 value);
+	} else {
+		ret = mmc_boot_wp(mmc);
+	}
+
+	return ret;
+}
+
+/**
+ * mmc_boot_wp_active_partition() - set write protection to active boot
+ * partition.
+ *
+ * @param mmc the mmc device.
+ */
+static int mmc_boot_wp_active_partition(struct mmc *mmc)
+{
+	u8 part;
+
+	if (mmc->part_config == MMCPART_NOAVAILABLE)
+		return -EOPNOTSUPP;
+
+	part = EXT_CSD_EXTRACT_BOOT_PART(mmc->part_config);
+
+	return mmc_boot_wp_single_partition(mmc, part - 1);
+}
+
 #if !CONFIG_IS_ENABLED(MMC_TINY)
 static int mmc_set_card_speed(struct mmc *mmc, enum bus_mode mode,
 			      bool hsdowngrade)
@@ -2925,6 +2979,10 @@ static int mmc_complete_init(struct mmc *mmc)
 		mmc->has_init = 0;
 	else
 		mmc->has_init = 1;
+
+	if (!err && CONFIG_IS_ENABLED(MMC_WRITE_PROTECT_ACTIVE_BOOT))
+		mmc_boot_wp_active_partition(mmc);
+
 	return err;
 }
 
-- 
2.34.1