[RFC PATCH] mmc: core: Update ext_csd if touched by ioctl

[Dirk Behme <dirk.behme@gmail.com>]

In case an ioctl changes an EXT_CSD register, update the internal ext_csd
data structure, too. Else the driver's internal ext_csd data structure and
the EXT_CSD register content doesn't match any more. In this case additional
ioctls changing the ext_csd would revert the initial one due to the old data
in the driver's internal ext_csd data.

E.g. using the mmc utils utility to enable the bootpart

mmc bootpart enable 1 0 /dev/mmcblk1

correctly writes to the EXT_CSD structure of the device, but
doesn't update

card->ext_csd.part_config

Issuing additional MMC_SWITCH commands afterwards use the then (wrong)
card->ext_csd.part_config. Resulting in an undo of the initial mmc bootpart
enable.

Fix this by updating the ext_csd in case of an EXT_CSD update ioctl.

Signed-off-by: Dirk Behme <dirk.behme@gmail.com>
---
Notes:

This fixes the issue discussed in

http://marc.info/?l=linux-mmc&m=137820629730918

This patch is marked as RFC due to two reasons:

* exporting mmc_update_ext_csd() in core/mmc.c and calling it directly from
  card/block.c
* It seems it's not allowed to call mmc_part_add() in mmc_read_ext_csd()
  several times. So this is disabled by passing an 'update' variable to
  mmc_read_ext_csd() disabling the mmc_part_add() in case we just want to
  update the ext_csd variables.

How can this be done better/cleaner?

 drivers/mmc/card/block.c |   14 ++++++++++++++
 drivers/mmc/core/mmc.c   |   26 ++++++++++++++++++++++----
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 1a3163f..0a4bd62 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -132,6 +132,8 @@ enum {
 module_param(perdev_minors, int, 0444);
 MODULE_PARM_DESC(perdev_minors, "Minors numbers to allocate per device");
 
+int mmc_update_ext_csd(struct mmc_card *card);
+
 static inline int mmc_blk_part_switch(struct mmc_card *card,
 				      struct mmc_blk_data *md);
 static int get_card_status(struct mmc_card *card, u32 *status, int retries);
@@ -600,6 +602,18 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
 					__func__, status, err);
 	}
 
+	if ((cmd.opcode == MMC_SWITCH) && ((cmd.arg >> 24) & 0x3)) {
+		/*
+		 * In case the IOCTL has modified the EXT_CSD,
+		 * update it, i.e. re-read the EXT_CSD.
+		 */
+		err = mmc_update_ext_csd(card);
+		if (err)
+			dev_err(mmc_dev(card->host),
+					"%s: EXT_CSD update failed, error %d\n",
+					__func__, err);
+	}
+
 cmd_rel_host:
 	mmc_put_card(card);
 
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 6d02012..5db9d8c 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -269,7 +269,7 @@ static void mmc_select_card_type(struct mmc_card *card)
 /*
  * Decode extended CSD.
  */
-static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
+static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd, int update)
 {
 	int err = 0, idx;
 	unsigned int part_size;
@@ -348,7 +348,8 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
 		 * There are two boot regions of equal size, defined in
 		 * multiples of 128K.
 		 */
-		if (ext_csd[EXT_CSD_BOOT_MULT] && mmc_boot_partition_access(card->host)) {
+		if (ext_csd[EXT_CSD_BOOT_MULT] && mmc_boot_partition_access(card->host) &&
+		    !update) {
 			for (idx = 0; idx < MMC_NUM_BOOT_PARTITION; idx++) {
 				part_size = ext_csd[EXT_CSD_BOOT_MULT] << 17;
 				mmc_part_add(card, part_size,
@@ -519,7 +520,8 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
 		 * RPMB regions are defined in multiples of 128K.
 		 */
 		card->ext_csd.raw_rpmb_size_mult = ext_csd[EXT_CSD_RPMB_MULT];
-		if (ext_csd[EXT_CSD_RPMB_MULT] && mmc_host_cmd23(card->host)) {
+		if (ext_csd[EXT_CSD_RPMB_MULT] && mmc_host_cmd23(card->host) &&
+		    !update) {
 			mmc_part_add(card, ext_csd[EXT_CSD_RPMB_MULT] << 17,
 				EXT_CSD_PART_CONFIG_ACC_RPMB,
 				"rpmb", 0, false,
@@ -983,7 +985,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 		err = mmc_get_ext_csd(card, &ext_csd);
 		if (err)
 			goto free_card;
-		err = mmc_read_ext_csd(card, ext_csd);
+		err = mmc_read_ext_csd(card, ext_csd, 0);
 		if (err)
 			goto free_card;
 
@@ -1634,6 +1636,22 @@ static void mmc_attach_bus_ops(struct mmc_host *host)
 	mmc_attach_bus(host, bus_ops);
 }
 
+int mmc_update_ext_csd(struct mmc_card *card)
+{
+	u8 *new_ext_csd;
+	int err;
+
+	err = mmc_get_ext_csd(card, &new_ext_csd);
+	if (err || new_ext_csd == NULL)
+		goto out;
+
+	err = mmc_read_ext_csd(card, new_ext_csd, 1);
+
+out:
+	mmc_free_ext_csd(new_ext_csd);
+	return err;
+}
+
 /*
  * Starting point for MMC card init.
  */
-- 
1.7.10.4