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[v4] dt-binding: mtd: nand: Document the cs-gpios property

Message ID 20210510171800.27225-1-miquel.raynal@bootlin.com
State Not Applicable
Headers show
Series [v4] dt-binding: mtd: nand: Document the cs-gpios property | expand

Checks

Context Check Description
robh/checkpatch success
robh/dt-meta-schema success
robh/dtbs-check fail build log

Commit Message

Miquel Raynal May 10, 2021, 5:18 p.m. UTC
To reach higher capacities, arrays of chips are now pretty common.
Unfortunately, most of the controllers have been designed a decade ago
and did not all anticipate the need for several chip-selects. The new
cs-gpios property allows to workaround this limitation by adding as many
GPIO chip-select as needed.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---

Resending only the binding patch of the series, with the following
changes requested by Rob:
* Fixed the coherency between cs-gpios and gpios-cs
* Added maxItems: 8 (this is a good enough value for most of the cases I
  guess, this can be increased later if needed).
* Adding maxItems: 8 lead to an error when checking the example,
  minItems: 8 had to be added as well to the schema to fix it, not sure
  this was expected or not.

 .../bindings/mtd/nand-controller.yaml          | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

Comments

Rob Herring May 11, 2021, 4:24 p.m. UTC | #1
On Mon, 10 May 2021 19:18:00 +0200, Miquel Raynal wrote:
> To reach higher capacities, arrays of chips are now pretty common.
> Unfortunately, most of the controllers have been designed a decade ago
> and did not all anticipate the need for several chip-selects. The new
> cs-gpios property allows to workaround this limitation by adding as many
> GPIO chip-select as needed.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
> 
> Resending only the binding patch of the series, with the following
> changes requested by Rob:
> * Fixed the coherency between cs-gpios and gpios-cs
> * Added maxItems: 8 (this is a good enough value for most of the cases I
>   guess, this can be increased later if needed).
> * Adding maxItems: 8 lead to an error when checking the example,
>   minItems: 8 had to be added as well to the schema to fix it, not sure
>   this was expected or not.
> 
>  .../bindings/mtd/nand-controller.yaml          | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 

Reviewed-by: Rob Herring <robh@kernel.org>
Miquel Raynal May 26, 2021, 9:03 a.m. UTC | #2
On Mon, 2021-05-10 at 17:18:00 UTC, Miquel Raynal wrote:
> To reach higher capacities, arrays of chips are now pretty common.
> Unfortunately, most of the controllers have been designed a decade ago
> and did not all anticipate the need for several chip-selects. The new
> cs-gpios property allows to workaround this limitation by adding as many
> GPIO chip-select as needed.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Rob Herring <robh@kernel.org>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next.

Miquel
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/mtd/nand-controller.yaml b/Documentation/devicetree/bindings/mtd/nand-controller.yaml
index 678b39952502..bd217e6f5018 100644
--- a/Documentation/devicetree/bindings/mtd/nand-controller.yaml
+++ b/Documentation/devicetree/bindings/mtd/nand-controller.yaml
@@ -38,6 +38,17 @@  properties:
 
   ranges: true
 
+  cs-gpios:
+    minItems: 1
+    maxItems: 8
+    description:
+      Array of chip-select available to the controller. The first
+      entries are a 1:1 mapping of the available chip-select on the
+      NAND controller (even if they are not used). As many additional
+      chip-select as needed may follow and should be phandles of GPIO
+      lines. 'reg' entries of the NAND chip subnodes become indexes of
+      this array when this property is present.
+
 patternProperties:
   "^nand@[a-f0-9]$":
     type: object
@@ -164,14 +175,19 @@  examples:
     nand-controller {
       #address-cells = <1>;
       #size-cells = <0>;
+      cs-gpios = <0>, <&gpioA 1>; /* A single native CS is available */
 
       /* controller specific properties */
 
       nand@0 {
-        reg = <0>;
+        reg = <0>; /* Native CS */
         nand-use-soft-ecc-engine;
         nand-ecc-algo = "bch";
 
         /* controller specific properties */
       };
+
+      nand@1 {
+        reg = <1>; /* GPIO CS */
+      };
     };