[PATCH v3 4/8] mtd: nand: atmel: Avoid ECC errors when leaving backup mode

[Romain Izard]

During backup mode, the contents of all registers will be cleared as the
SoC will be completely powered down. For a product that boots on NAND
Flash memory, the bootloader will obviously use the related controller
to read the Flash and correct any detected error in the memory, before
handling back control to the kernel's resuming entry point.

But it does not clean the NAND controller registers after use and on its
side the kernel driver expects the error locator to be powered down and
in a clean state. Add a resume hook for the PMECC error locator, and
reset its registers.

Signed-off-by: Romain Izard <romain.izard.pro@xxxxxxxxx>
---
Change in v3:
* keep the PMECC disabled when not in use, and use atmel_pmecc_resume to
  reset the controller after the bootloader has left it enabled.

 drivers/mtd/nand/atmel/nand-controller.c |  3 +++
 drivers/mtd/nand/atmel/pmecc.c           | 22 ++++++++++++++--------
 drivers/mtd/nand/atmel/pmecc.h           |  1 +
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/mtd/nand/atmel/nand-controller.c b/drivers/mtd/nand/atmel/nand-controller.c
index f25eca79f4e5..86c2199380c2 100644
--- a/drivers/mtd/nand/atmel/nand-controller.c
+++ b/drivers/mtd/nand/atmel/nand-controller.c
@@ -2530,6 +2530,9 @@ static __maybe_unused int atmel_nand_controller_resume(struct device *dev)
 	struct atmel_nand_controller *nc = dev_get_drvdata(dev);
 	struct atmel_nand *nand;
 
+	if (nand->pmecc)
+		atmel_pmecc_resume(nand->pmecc);
+
 	list_for_each_entry(nand, &nc->chips, node) {
 		int i;
 
diff --git a/drivers/mtd/nand/atmel/pmecc.c b/drivers/mtd/nand/atmel/pmecc.c
index 146af8218314..ff09c0f25dd4 100644
--- a/drivers/mtd/nand/atmel/pmecc.c
+++ b/drivers/mtd/nand/atmel/pmecc.c
@@ -765,6 +765,12 @@ void atmel_pmecc_get_generated_eccbytes(struct atmel_pmecc_user *user,
 }
 EXPORT_SYMBOL_GPL(atmel_pmecc_get_generated_eccbytes);
 
+void atmel_pmecc_reset(struct atmel_pmecc *pmecc)
+{
+	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
+	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
+}
+
 int atmel_pmecc_enable(struct atmel_pmecc_user *user, int op)
 {
 	struct atmel_pmecc *pmecc = user->pmecc;
@@ -797,14 +803,17 @@ EXPORT_SYMBOL_GPL(atmel_pmecc_enable);
 
 void atmel_pmecc_disable(struct atmel_pmecc_user *user)
 {
-	struct atmel_pmecc *pmecc = user->pmecc;
-
-	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
-	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
+	atmel_pmecc_reset(user->pmecc);
 	mutex_unlock(&user->pmecc->lock);
 }
 EXPORT_SYMBOL_GPL(atmel_pmecc_disable);
 
+void atmel_pmecc_resume(struct atmel_pmecc_user *user)
+{
+	atmel_pmecc_reset(user->pmecc);
+}
+EXPORT_SYMBOL_GPL(atmel_pmecc_resume);
+
 int atmel_pmecc_wait_rdy(struct atmel_pmecc_user *user)
 {
 	struct atmel_pmecc *pmecc = user->pmecc;
@@ -855,10 +864,7 @@ static struct atmel_pmecc *atmel_pmecc_create(struct platform_device *pdev,
 
 	/* Disable all interrupts before registering the PMECC handler. */
 	writel(0xffffffff, pmecc->regs.base + ATMEL_PMECC_IDR);
-
-	/* Reset the ECC engine */
-	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
-	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
+	atmel_pmecc_reset(pmecc);
 
 	return pmecc;
 }
diff --git a/drivers/mtd/nand/atmel/pmecc.h b/drivers/mtd/nand/atmel/pmecc.h
index a8ddbfca2ea5..488a90f1965d 100644
--- a/drivers/mtd/nand/atmel/pmecc.h
+++ b/drivers/mtd/nand/atmel/pmecc.h
@@ -63,6 +63,7 @@ void atmel_pmecc_destroy_user(struct atmel_pmecc_user *user);
 
 int atmel_pmecc_enable(struct atmel_pmecc_user *user, int op);
 void atmel_pmecc_disable(struct atmel_pmecc_user *user);
+void atmel_pmecc_resume(struct atmel_pmecc_user *user);
 int atmel_pmecc_wait_rdy(struct atmel_pmecc_user *user);
 int atmel_pmecc_correct_sector(struct atmel_pmecc_user *user, int sector,
 			       void *data, void *ecc);
-- 
2.11.0