[PATCH] mtd: spi-nor: Decouple SPI NOR's device_node from controller device

[Marek Vasut]

The problem this patch is trying to address is such, that SPI NOR flash
devices attached to a dedicated SPI NOR controller cannot read their
properties from the associated struct device_node.

A couple of facts first:
1) Each SPI NOR flash has a struct spi_nor associated with it.
2) Each SPI NOR flash has certain device properties associated
   with it, for example the OF property 'm25p,fast-read' is a
   good pick. These properties are used by the SPI NOR core to
   select which opcodes are sent to such SPI NOR flash. These
   properties are coming from spi_nor .dev->device_node .

The problem is, that for SPI NOR controllers, the struct spi_nor .dev
element points to the struct device of the SPI NOR controller, not the
SPI NOR flash. Therefore, the associated dev->device_node also is the
one of the controller and therefore the SPI NOR core code is trying to
parse the SPI NOR controller's properties, not the properties of the
SPI NOR flash.

Note: The m25p80 driver is not affected, because the controller and
      the flash are the same device, so the associated device_node
      of the controller and the flash are the same.

This patch adjusts the SPI NOR core such that the device_node is not
picked from spi_nor .dev directly, but from a new separate spi_nor .dn
element. This let's the SPI NOR controller drivers set up a different
spi_nor .dn element for each SPI NOR flash.

This patch also fixes the controller drivers to be compatible with
this modification and correctly set the spi_nor .dn element.

This patch is inspired by 5844feeaa4154d1c46d3462c7a4653d22356d8b4
mtd: nand: add common DT init code

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Brian Norris <computersforpeace at gmail.com>
---
 drivers/mtd/devices/m25p80.c      | 1 +
 drivers/mtd/spi-nor/fsl-quadspi.c | 1 +
 drivers/mtd/spi-nor/nxp-spifi.c   | 1 +
 include/linux/mtd/spi-nor.h       | 3 +++
 4 files changed, 6 insertions(+)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index 9cd3631..725320f 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -202,6 +202,7 @@ static int m25p_probe(struct spi_device *spi)
 
 	nor->dev = &spi->dev;
 	nor->mtd = &flash->mtd;
+	nor->dn = &spi->dev.of_node;
 	nor->priv = flash;
 
 	spi_set_drvdata(spi, flash);
diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c b/drivers/mtd/spi-nor/fsl-quadspi.c
index d32b7e0..f918a60 100644
--- a/drivers/mtd/spi-nor/fsl-quadspi.c
+++ b/drivers/mtd/spi-nor/fsl-quadspi.c
@@ -1017,6 +1017,7 @@ static int fsl_qspi_probe(struct platform_device *pdev)
 
 		nor->mtd = mtd;
 		nor->dev = dev;
+		nor->dn = np;
 		nor->priv = q;
 		mtd->priv = nor;
 
diff --git a/drivers/mtd/spi-nor/nxp-spifi.c b/drivers/mtd/spi-nor/nxp-spifi.c
index 9ad1dd0..3ed4564 100644
--- a/drivers/mtd/spi-nor/nxp-spifi.c
+++ b/drivers/mtd/spi-nor/nxp-spifi.c
@@ -334,6 +334,7 @@ static int nxp_spifi_setup_flash(struct nxp_spifi *spifi,
 	spifi->mtd.priv  = &spifi->nor;
 	spifi->nor.mtd   = &spifi->mtd;
 	spifi->nor.dev   = spifi->dev;
+	spifi->nor.dn    = np;
 	spifi->nor.priv  = spifi;
 	spifi->nor.read  = nxp_spifi_read;
 	spifi->nor.write = nxp_spifi_write;
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 1bf6f11..333999d 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -169,6 +169,7 @@ enum spi_nor_option_flags {
  * @lock:		[FLASH-SPECIFIC] lock a region of the SPI NOR
  * @unlock:		[FLASH-SPECIFIC] unlock a region of the SPI NOR
  * @priv:		the private data
+ * @dn:			[BOARD-SPECIFIC] device node describing this instance
  */
 struct spi_nor {
 	struct mtd_info		*mtd;
@@ -208,6 +209,8 @@ struct spi_nor {
 	int (*flash_unlock)(struct spi_nor *nor, loff_t ofs, uint64_t len);
 
 	void *priv;
+
+	struct device_node *dn;
 };
 
 /**
-- 
2.1.4