mtd: rawnand: Add the ->choose_interface_config() hook

This hook can be overloaded by NAND manufacturer drivers to propose
alternative timings when not following the main standards. In this
case, the manufacturer drivers is responsible for choosing the best
interface configuration that fits both the controller and chip
capabilities.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200529111322.7184-23-miquel.raynal@bootlin.com

drivers/mtd/nand/raw/nand_base.c

@@ -1066,18 +1066,23 @@ int nand_choose_best_sdr_timings(struct nand_chip *chip,
  * @chip: The NAND chip
  *
  * Find the best data interface and NAND timings supported by the chip
- * and the driver.
- * First tries to retrieve supported timing modes from ONFI information,
- * and if the NAND chip does not support ONFI, relies on the
- * ->onfi_timing_mode_default specified in the nand_ids table. After this
- * function nand_chip->interface_ is initialized with the best timing mode
- * available.
+ * and the driver. Eventually let the NAND manufacturer driver propose his own
+ * set of timings.
+ *
+ * After this function nand_chip->interface_config is initialized with the best
+ * timing mode available.
+ *
+ * Returns 0 for success or negative error code otherwise.
  */
 static int nand_choose_interface_config(struct nand_chip *chip)
 {
 	if (!nand_controller_can_setup_interface(chip))
 		return 0;
 
+	if (chip->ops.choose_interface_config)
+		return chip->ops.choose_interface_config(chip,
+							 &chip->interface_config);
+
 	return nand_choose_best_sdr_timings(chip, &chip->interface_config,
 					    NULL);
 }

include/linux/mtd/rawnand.h

@@ -1033,6 +1033,7 @@ 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_interface_config: Choose the best interface configuration
  */
 struct nand_chip_ops {
 	int (*suspend)(struct nand_chip *chip);
@@ -1040,6 +1041,8 @@ 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_interface_config)(struct nand_chip *chip,
+				       struct nand_interface_config *iface);
 };
 
 /**