[PATCH 2/2] mci: core: reset ERASE_GRP_DEF on startup

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

EXT_CSD register EXT_CSD_ERASE_GROUP_DEF loses its value after power
cycles and needs to be reset. Quoting the eMMC 5.1 standard[1]:

  After every power-up, when the host uses a device that partition(s)
  are configured, it must set the ERASE_GROUP_DEF bit to high before
  issuing read, write, erase and write protect commands, because this
  bit is reset after power-up. Otherwise, these may not work correctly
  and it may leave the stored data in an unknown state.

[1]: JESD84-B51

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/mci/mci-core.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
index 6d55eb8305b9..098c67f0102b 100644
--- a/drivers/mci/mci-core.c
+++ b/drivers/mci/mci-core.c
@@ -1218,11 +1218,24 @@ static void mci_extract_block_lengths_from_csd(struct mci *mci)
 }
 
 /**
- * Extract erase group size
+ * Configure erase group size
  * @param mci MCI instance
  */
-static void mci_extract_erase_group_size(struct mci *mci)
+static void mci_configure_erase_group_size(struct mci *mci)
 {
+	/* Enable ERASE_GRP_DEF. This bit is lost after a reset or power off.
+	 * This needs to happen even if we don't have erase support compiled-in.
+	 */
+	if (!IS_SD(mci) && mci->version >= MMC_VERSION_4_3) { 
+		int err;
+
+		err = mci_switch(mci, EXT_CSD_ERASE_GROUP_DEF, 1);
+		if (err)
+			dev_warn(&mci->dev, "failed erase group switch\n");
+		else
+			mci->ext_csd[EXT_CSD_ERASE_GROUP_DEF] = 1;
+	}
+
 	if (!IS_ENABLED(CONFIG_MCI_ERASE) ||
 	    !(UNSTUFF_BITS(mci->csd, 84, 12) & CCC_ERASE))
 		return;
@@ -1954,7 +1967,7 @@ static int mci_startup(struct mci *mci)
 	dev_info(&mci->dev, "detected %s card version %s\n", IS_SD(mci) ? "SD" : "MMC",
 		mci_version_string(mci));
 	mci_extract_card_capacity_from_csd(mci);
-	mci_extract_erase_group_size(mci);
+	mci_configure_erase_group_size(mci);
 
 	if (IS_SD(mci))
 		err = mci_startup_sd(mci);
-- 
2.39.5