[PATCH v4 18/19] mtd: rawnand: Add the ->choose_data_interface() hook

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

This hook can be overloaded by NAND manufacturer drivers to propose
alternative timings when not following the main standards.

Vendors implementing this hook should:
1- choose the best timings and fill the data interface,
2- verify that the controller supports them.

Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
---
 drivers/mtd/nand/raw/internals.h | 5 +++++
 drivers/mtd/nand/raw/nand_base.c | 8 ++++++++
 include/linux/mtd/rawnand.h      | 2 ++
 3 files changed, 15 insertions(+)

diff --git a/drivers/mtd/nand/raw/internals.h b/drivers/mtd/nand/raw/internals.h
index 9af6979257e2..61edbab35068 100644
--- a/drivers/mtd/nand/raw/internals.h
+++ b/drivers/mtd/nand/raw/internals.h
@@ -146,6 +146,11 @@ static inline bool nand_controller_has_setup_data_iface(struct nand_chip *chip)
 	return true;
 }
 
+static inline bool nand_can_choose_data_interface(struct nand_chip *chip)
+{
+	return chip->ops.choose_data_interface;
+}
+
 /* BBT functions */
 int nand_markbad_bbt(struct nand_chip *chip, loff_t offs);
 int nand_isreserved_bbt(struct nand_chip *chip, loff_t offs);
diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index d9fe7795f183..e9df339849d3 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -1060,6 +1060,14 @@ static int nand_choose_data_interface(struct nand_chip *chip)
 	if (!nand_controller_has_setup_data_iface(chip))
 		return 0;
 
+	/*
+	 * Let the NAND vendor hook identify the best timings.
+	 * ->choose_data_interface() is expected to update the entire chip's
+	 * nand_data_interface structure.
+	 */
+	if (nand_can_choose_data_interface(chip))
+		return chip->ops.choose_data_interface(chip);
+
 	/*
 	 * First try to identify the best timings from ONFI parameters and
 	 * if the NAND does not support ONFI, fallback to the default ONFI
diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
index a4b68e7b246a..5b8b94521a18 100644
--- a/include/linux/mtd/rawnand.h
+++ b/include/linux/mtd/rawnand.h
@@ -1034,6 +1034,7 @@ struct nand_legacy {
  * @lock_area: Lock operation
  * @unlock_area: Unlock operation
  * @setup_read_retry: Set the read-retry mode (mostly needed for MLC NANDs)
+ * @choose_data_interface: Choose the best data interface
  */
 struct nand_chip_ops {
 	int (*suspend)(struct nand_chip *chip);
@@ -1041,6 +1042,7 @@ struct nand_chip_ops {
 	int (*lock_area)(struct nand_chip *chip, loff_t ofs, uint64_t len);
 	int (*unlock_area)(struct nand_chip *chip, loff_t ofs, uint64_t len);
 	int (*setup_read_retry)(struct nand_chip *chip, int retry_mode);
+	int (*choose_data_interface)(struct nand_chip *chip);
 };
 
 /**
-- 
2.20.1


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