For implementing the proposed solution the current 'stacked-memories' &
'parallel-memories' bindings need to be updated as follow.

stacked-memories binding changes:
- Each flash will have its own flash node. This approach allows flashes of
  different makes and sizes to be stacked together, as each flash will be
  probed individually.
- Each of the flash node will have its own “reg” property that will contain
  its physical CS.
- Remove the size information from the bindings as it can be retrived
  drirectly from the flash.
- The stacked-memories DT bindings will contain the phandles of the flash
  nodes connected in stacked mode.

The new layer will update the mtd->size and other mtd_info parameters after
both the flashes are probed and will call mtd_device_register with the
combined information.

spi@0 {
        ...
        flash@0 {
                compatible = "jedec,spi-nor"
                reg = <0x00>;
                stacked-memories = <&flash@0 &flash@1>;
                spi-max-frequency = <50000000>;
                ...
                        partitions {
                        compatible = "fixed-partitions";
                                concat-partition = <&flash0_partition &flash1_partition>;
                                flash0_partition: partition@0 {
                                        label = "part0_0";
                                        reg = <0x0 0x800000>;
                                }
                        }
        }
        flash@1 {
                compatible = "jedec,spi-nor"
                reg = <0x01>;
                stacked-memories = <&flash@0 &flash@1>;
                spi-max-frequency = <50000000>;
                ...
                        partitions {
                        compatible = "fixed-partitions";
                                concat-partition = <&flash0_partition &flash1_partition>;
                                flash1_partition: partition@0 {
                                        label = "part0_1";
                                        reg = <0x0 0x800000>;
                                }
                        }
        }

}

parallel-memories binding changes:
- Remove the size information from the bindings and change the type to
  boolen.
- Each flash connected in parallel mode should be identical and will have
  one flash node for both the flash devices.
- The “reg” prop will contain the physical CS number for both the connected
  flashes.

The new layer will double the mtd-> size and register it with the mtd layer.

spi@1 {
        ...
        flash@3 {
                compatible = "jedec,spi-nor"
                reg = <0x00 0x01>;
                paralle-memories ;
                spi-max-frequency = <50000000>;
                ...
                        partitions {
                        compatible = "fixed-partitions";
                                flash0_partition: partition@0 {
                                        label = "part0_0";
                                        reg = <0x0 0x800000>;
                                }
                        }
        }
}

Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com>
---
 .../bindings/spi/spi-controller.yaml          | 23 +++++++++++++++++--
 .../bindings/spi/spi-peripheral-props.yaml    |  9 +++-----
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/Documentation/devicetree/bindings/spi/spi-controller.yaml b/Documentation/devicetree/bindings/spi/spi-controller.yaml
index 093150c0cb87..2d300f98dd72 100644
--- a/Documentation/devicetree/bindings/spi/spi-controller.yaml
+++ b/Documentation/devicetree/bindings/spi/spi-controller.yaml
@@ -185,7 +185,26 @@ examples:
         flash@2 {
             compatible = "jedec,spi-nor";
             spi-max-frequency = <50000000>;
-            reg = <2>, <3>;
-            stacked-memories = /bits/ 64 <0x10000000 0x10000000>;
+            reg = <2>;
+            stacked-memories = <&flash0 &flash1>;
         };
+
     };
+
+  - |
+    spi@90010000 {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        compatible = "fsl,imx28-spi";
+        reg = <0x90010000 0x2000>;
+        interrupts = <96>;
+        dmas = <&dma_apbh 0>;
+        dma-names = "rx-tx";
+
+        flash@0 {
+            compatible = "jedec,spi-nor";
+            spi-max-frequency = <50000000>;
+            reg = <0>, <1>;
+            parallel-memories;
+        };
+      };
diff --git a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
index 15938f81fdce..2a014160d701 100644
--- a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
+++ b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
@@ -96,7 +96,7 @@ properties:
       space with only a single additional wire, while still needing
       to repeat the commands when crossing a chip boundary. The size of
       each chip should be provided as members of the array.
-    $ref: /schemas/types.yaml#/definitions/uint64-array
+    $ref: /schemas/types.yaml#/definitions/phandle-array
     minItems: 2
     maxItems: 4
 
@@ -107,11 +107,8 @@ properties:
       different memories (eg. even bits are stored in one memory, odd
       bits in the other). This basically doubles the address space and
       the throughput while greatly complexifying the wiring because as
-      many busses as devices must be wired. The size of each chip should
-      be provided as members of the array.
-    $ref: /schemas/types.yaml#/definitions/uint64-array
-    minItems: 2
-    maxItems: 4
+      many busses as devices must be wired.
+    $ref: /schemas/types.yaml#/definitions/flag
 
   st,spi-midi-ns:
     description: |
-- 
2.34.1

Hi Amit,

On 26/10/2024 at 13:23:47 +0530, Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com> wrote:

> For implementing the proposed solution the current 'stacked-memories' &
> 'parallel-memories' bindings need to be updated as follow.
>
> stacked-memories binding changes:
> - Each flash will have its own flash node. This approach allows flashes of
>   different makes and sizes to be stacked together, as each flash will be
>   probed individually.
> - Each of the flash node will have its own “reg” property that will contain
>   its physical CS.
> - Remove the size information from the bindings as it can be retrived
>   drirectly from the flash.
> - The stacked-memories DT bindings will contain the phandles of the flash
>   nodes connected in stacked mode.
>
> The new layer will update the mtd->size and other mtd_info parameters after
> both the flashes are probed and will call mtd_device_register with the
> combined information.
>
> spi@0 {
>         ...
>         flash@0 {
>                 compatible = "jedec,spi-nor"
>                 reg = <0x00>;
>                 stacked-memories = <&flash@0 &flash@1>;
>                 spi-max-frequency = <50000000>;
>                 ...
>                         partitions {
>                         compatible = "fixed-partitions";
>                                 concat-partition = <&flash0_partition &flash1_partition>;
>                                 flash0_partition: partition@0 {
>                                         label = "part0_0";
>                                         reg = <0x0 0x800000>;
>                                 }
>                         }
>         }
>         flash@1 {
>                 compatible = "jedec,spi-nor"
>                 reg = <0x01>;
>                 stacked-memories = <&flash@0 &flash@1>;
>                 spi-max-frequency = <50000000>;
>                 ...
>                         partitions {

Same comment as before here.

>                         compatible = "fixed-partitions";
>                                 concat-partition = <&flash0_partition &flash1_partition>;
>                                 flash1_partition: partition@0 {
>                                         label = "part0_1";
>                                         reg = <0x0 0x800000>;
>                                 }
>                         }
>         }
>
> }
>
> parallel-memories binding changes:
> - Remove the size information from the bindings and change the type to
>   boolen.
> - Each flash connected in parallel mode should be identical and will have
>   one flash node for both the flash devices.
> - The “reg” prop will contain the physical CS number for both the connected
>   flashes.
>
> The new layer will double the mtd-> size and register it with the mtd
> layer.

Not so sure about that, you'll need a new mtd device to capture the
whole device. But this is implementation related, not relevant for
binding.

>
> spi@1 {
>         ...
>         flash@3 {
>                 compatible = "jedec,spi-nor"
>                 reg = <0x00 0x01>;
>                 paralle-memories ;

Please fix the typos and the spacing (same above).

>                 spi-max-frequency = <50000000>;
>                 ...
>                         partitions {
>                         compatible = "fixed-partitions";
>                                 flash0_partition: partition@0 {
>                                         label = "part0_0";
>                                         reg = <0x0 0x800000>;
>                                 }
>                         }
>         }
> }
>
> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com>
> ---
>  .../bindings/spi/spi-controller.yaml          | 23 +++++++++++++++++--
>  .../bindings/spi/spi-peripheral-props.yaml    |  9 +++-----
>  2 files changed, 24 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/spi/spi-controller.yaml b/Documentation/devicetree/bindings/spi/spi-controller.yaml
> index 093150c0cb87..2d300f98dd72 100644
> --- a/Documentation/devicetree/bindings/spi/spi-controller.yaml
> +++ b/Documentation/devicetree/bindings/spi/spi-controller.yaml
> @@ -185,7 +185,26 @@ examples:
>          flash@2 {
>              compatible = "jedec,spi-nor";
>              spi-max-frequency = <50000000>;
> -            reg = <2>, <3>;
> -            stacked-memories = /bits/ 64 <0x10000000 0x10000000>;
> +            reg = <2>;
> +            stacked-memories = <&flash0 &flash1>;
>          };

I'm sorry but this is not what you've talked about in this series.
Either you have flash0 and flash1 and use the stacked-memories property
in both of them (which is what you described) or you create a third
virtual device which points to two other flashes. This example allows
for an easier use of the partitions mechanism on top of a virtual mtd
device but, heh, you're now describing a virtual mtd device, which is
not a physical device as it "should" be.

Thanks,
Miquèl