[PATCH v1 1/2] devicetree: bindings: improve description for GPIO assisted NAND flash

[PATCH v1 1/2] devicetree: bindings: improve description for GPIO assisted NAND flash

[Gerhard Sittig]

Expand the description of the 'gpios' property in the GPIO assisted
NAND flash binding, to explicitly list the required GPIO pin references
and their order.

Update the example section to individually bracket the GPIO references,
and capitalize the signal names for improved readability.

Signed-off-by: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>
---
 .../devicetree/bindings/mtd/gpio-control-nand.txt        |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/mtd/gpio-control-nand.txt b/Documentation/devicetree/bindings/mtd/gpio-control-nand.txt
index 36ef07d3c90f..af8915b41ccf 100644
--- a/Documentation/devicetree/bindings/mtd/gpio-control-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/gpio-control-nand.txt
@@ -11,8 +11,8 @@ Required properties:
   are made in native endianness.
 - #address-cells, #size-cells : Must be present if the device has sub-nodes
   representing partitions.
-- gpios : specifies the gpio pins to control the NAND device.  nwp is an
-  optional gpio and may be set to 0 if not present.
+- gpios : Specifies the GPIO pins to control the NAND device.  The order of
+  GPIO references is:  RDY, nCE, ALE, CLE, and an optional nWP.
 
 Optional properties:
 - bank-width : Width (in bytes) of the device.  If not present, the width
@@ -35,11 +35,11 @@ gpio-nand@1,0 {
 	reg = <1 0x0000 0x2>;
 	#address-cells = <1>;
 	#size-cells = <1>;
-	gpios = <&banka 1 0	/* rdy */
-		 &banka 2 0 	/* nce */
-		 &banka 3 0 	/* ale */
-		 &banka 4 0 	/* cle */
-		 0		/* nwp */>;
+	gpios = <&banka 1 0>,	/* RDY */
+		<&banka 2 0>, 	/* nCE */
+		<&banka 3 0>, 	/* ALE */
+		<&banka 4 0>, 	/* CLE */
+		<0>;		/* nWP */
 
 	partition@0 {
 	...
-- 
1.7.10.4

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[PATCH v1 2/2] mtd: nand: gpio: improve comments about GPIO assisted operation

[Gerhard Sittig]

The drivers/mtd/nand/gpio.c driver does not GPIO bitbang the complete
NAND protocol, but instead is GPIO _assisted_ -- a memory mapped interface
communicates commands and data, and only few control signals are connected
to GPIO pins.

Expand comments in the driver source and in the Kconfig description to
better reflect the very nature of the driver.  The previous text could be
mistaken for complete GPIO bitbanging.

Signed-off-by: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>
---
 drivers/mtd/nand/Kconfig |    6 ++++--
 drivers/mtd/nand/gpio.c  |    4 +++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index f1cf503517fd..0ef8b35b459f 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -75,10 +75,12 @@ config MTD_NAND_DENALI_SCRATCH_REG_ADDR
           boards, the scratch register is at 0xFF108018.
 
 config MTD_NAND_GPIO
-	tristate "GPIO NAND Flash driver"
+	tristate "GPIO assisted NAND Flash driver"
 	depends on GPIOLIB
 	help
-	  This enables a GPIO based NAND flash driver.
+	  This enables a NAND flash driver where control signals are
+	  connected to GPIO pins, and commands and data are communicated
+	  via a memory mapped interface.
 
 config MTD_NAND_AMS_DELTA
 	tristate "NAND Flash device on Amstrad E3"
diff --git a/drivers/mtd/nand/gpio.c b/drivers/mtd/nand/gpio.c
index 117ce333fdd4..226eda6f2eee 100644
--- a/drivers/mtd/nand/gpio.c
+++ b/drivers/mtd/nand/gpio.c
@@ -8,7 +8,9 @@
  *
  * © 2004 Simtec Electronics
  *
- * Device driver for NAND connected via GPIO
+ * Device driver for NAND flash that uses a memory mapped interface to
+ * read/write the NAND commands and data, and GPIO pins for control signals
+ * (the DT binding refers to this as "GPIO assisted NAND flash")
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
-- 
1.7.10.4

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Re: [PATCH v1 1/2] devicetree: bindings: improve description for GPIO assisted NAND flash

[Brian Norris]

On Tue, Aug 05, 2014 at 10:37:25AM +0200, Gerhard Sittig wrote:
> Expand the description of the 'gpios' property in the GPIO assisted
> NAND flash binding, to explicitly list the required GPIO pin references
> and their order.
> 
> Update the example section to individually bracket the GPIO references,
> and capitalize the signal names for improved readability.
> 
> Signed-off-by: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>

Applied both to l2-mtd.git.

Brian
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