mtd: spi-nor: Add default_init() hook to tweak flash parameters

As of now, the flash parameters initialization logic is as following:

a/ default flash parameters init in spi_nor_init_params()
b/ manufacturer specific flash parameters updates, split across entire
   spi-nor core code
c/ flash parameters updates based on SFDP tables
d/ post BFPT flash parameter updates

In the quest of removing the manufacturer specific code from the spi-nor
core, we want to impose a timeline/priority on how the flash parameters
are updated. The following sequence of calls is pursued:

1/ spi-nor core parameters init based on 'flash_info' struct:
	spi_nor_info_init_params()

which can be overwritten by:
2/ MFR-based manufacturer flash parameters init:
	nor->manufacturer->fixups->default_init()

which can be overwritten by:
3/ specific flash_info tweeks done when decisions can not be done just on
   MFR:
	nor->info->fixups->default_init()

which can be overwritten by:
4/ SFDP tables flash parameters init - SFDP knows better:
	spi_nor_sfdp_init_params()

which can be overwritten by:
5/ post SFDP tables flash parameters updates - in case manufacturers get
   the serial flash tables wrong or incomplete.
	nor->info->fixups->post_sfdp()
   The later can be extended to nor->manufacturer->fixups->post_sfdp() if
   needed.

This patch opens doors for steps 2/ and 3/.
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>

drivers/mtd/spi-nor/spi-nor.c

@@ -154,12 +154,16 @@ struct sfdp_bfpt {
 
 /**
  * struct spi_nor_fixups - SPI NOR fixup hooks
+ * @default_init: called after default flash parameters init. Used to tweak
+ *                flash parameters when information provided by the flash_info
+ *                table is incomplete or wrong.
  * @post_bfpt: called after the BFPT table has been parsed
  *
  * Those hooks can be used to tweak the SPI NOR configuration when the SFDP
  * table is broken or not available.
  */
 struct spi_nor_fixups {
+	void (*default_init)(struct spi_nor *nor);
 	int (*post_bfpt)(struct spi_nor *nor,
 			 const struct sfdp_parameter_header *bfpt_header,
 			 const struct sfdp_bfpt *bfpt,
@@ -4133,6 +4137,17 @@ static int spi_nor_parse_sfdp(struct spi_nor *nor,
 	return err;
 }
 
+/**
+ * spi_nor_manufacturer_init_params() - Initialize the flash's parameters and
+ * settings based on ->default_init() hook.
+ * @nor:	pointer to a 'struct spi-nor'.
+ */
+static void spi_nor_manufacturer_init_params(struct spi_nor *nor)
+{
+	if (nor->info->fixups && nor->info->fixups->default_init)
+		nor->info->fixups->default_init(nor);
+}
+
 static int spi_nor_init_params(struct spi_nor *nor)
 {
 	struct spi_nor_flash_parameter *params = &nor->params;
@@ -4233,6 +4248,8 @@ static int spi_nor_init_params(struct spi_nor *nor)
 			params->quad_enable = info->quad_enable;
 	}
 
+	spi_nor_manufacturer_init_params(nor);
+
 	if ((info->flags & (SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ)) &&
 	    !(info->flags & SPI_NOR_SKIP_SFDP)) {
 		struct spi_nor_flash_parameter sfdp_params;