[PATCH v3 3/3] mtd: spinand: add SPI-NAND MTD resume handler

[<patrice.chotard@foss.st.com>]

From: Patrice Chotard <patrice.chotard@foss.st.com>

After power up, all SPI NAND's blocks are locked. Only read operations
are allowed, write and erase operations are forbidden.
The SPI NAND framework unlocks all the blocks during its initialization.

During a standby low power, the memory is powered down, losing its
configuration.
During the resume, the QSPI driver state is restored but the SPI NAND
framework does not reconfigured the memory.

This patch adds SPI-NAND MTD PM handlers for resume ops.
SPI NAND resume op re-initializes SPI NAND flash to its probed state.

Signed-off-by: Christophe Kerello <christophe.kerello@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
---
Changes in v3:
  - Add spinand_read_cfg() call to repopulate cache

Changes in v2:
  - Add helper spinand_block_unlock().
  - Add spinand_ecc_enable() call.
  - Remove some dev_err().
  - Fix commit's title and message.

 drivers/mtd/nand/spi/core.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 1f699ad84f1b..e3fcbcf381c3 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -1099,6 +1099,38 @@ static int spinand_block_unlock(struct spinand_device *spinand)
 	return ret;
 }
 
+static void spinand_mtd_resume(struct mtd_info *mtd)
+{
+	struct spinand_device *spinand = mtd_to_spinand(mtd);
+	int ret;
+
+	ret = spinand_reset_op(spinand);
+	if (ret)
+		return;
+
+	ret = spinand_read_cfg(spinand);
+	if (ret)
+		return;
+
+	ret = spinand_init_quad_enable(spinand);
+	if (ret)
+		return;
+
+	ret = spinand_upd_cfg(spinand, CFG_OTP_ENABLE, 0);
+	if (ret)
+		return;
+
+	ret = spinand_manufacturer_init(spinand);
+	if (ret)
+		return;
+
+	ret = spinand_block_unlock(spinand);
+	if (ret)
+		return;
+
+	spinand_ecc_enable(spinand, false);
+}
+
 static int spinand_init(struct spinand_device *spinand)
 {
 	struct device *dev = &spinand->spimem->spi->dev;
@@ -1186,6 +1218,7 @@ static int spinand_init(struct spinand_device *spinand)
 	mtd->_block_isreserved = spinand_mtd_block_isreserved;
 	mtd->_erase = spinand_mtd_erase;
 	mtd->_max_bad_blocks = nanddev_mtd_max_bad_blocks;
+	mtd->_resume = spinand_mtd_resume;
 
 	if (nand->ecc.engine) {
 		ret = mtd_ooblayout_count_freebytes(mtd);
-- 
2.17.1