spi: add multi-lane support

Merge series from David Lechner <dlechner@baylibre.com>:

This series is adding support for SPI controllers and peripherals that
have multiple SPI data lanes (data lanes being independent sets of
SDI/SDO lines, each with their own serializer/deserializer).

This series covers this specific use case:

+--------------+    +---------+
| SPI          |    | SPI     |
| Controller   |    | ADC     |
|              |    |         |
|          CS0 |--->| CS      |
|         SCLK |--->| SCLK    |
|          SDO |--->| SDI     |
|         SDI0 |<---| SDOA    |
|         SDI1 |<---| SDOB    |
|         SDI2 |<---| SDOC    |
|         SDI3 |<---| SDOD    |
+--------------+     +--------+

The ADC is a simultaneous sampling ADC that can convert 4 samples at the
same time. It has 4 data output lines (SDOA-D) that each contain the
data of one of the 4 channels. So it requires a SPI controller with 4
separate deserializers in order to receive all of the information at the
same time.

This should also work for the use case in [1] as well. (Some of the
patches in this series were already submitted there). In that case the
SPI controller is used kind of like it is two separate SPI controllers,
each with its own chip select, clock, and data lines.

[1]: https://lore.kernel.org/linux-spi/20250616220054.3968946-1-sean.anderson@linux.dev/

The DT bindings are a fairly straight-forward mapping of which pins on
the peripheral are connected to which pins on the controller. The SPI
core code parses this and makes the information available to drivers.
When a peripheral driver sees that multiple data lanes are wired up, it
can chose to use them when sending messages.

The SPI message API is a bit higher-level than just specifying the
number of data lines for a SPI transfer though. I did some research on
other SPI controllers that have this feature. They tend to be the kind
meant for connecting to two flash memory chips at the same time but can
be used more generically as well. They generally have the option to
either use one lane at a time (Sean's use case), or can mirror the same
data on multiple lanes (no users of this yet) or can perform striping
of a single data FIFO/DMA stream to/from the two lanes (our use case).

For now, the API assumes that if you want to do mirror/striping, then
you want to use all available data lanes. Otherwise, it just uses the
first data lane for "normal" SPI transfers.

Author: broonie

Documentation/devicetree/bindings/display/panel/sitronix,st7789v.yaml

@@ -34,8 +34,9 @@ properties:
   spi-cpol: true
 
   spi-rx-bus-width:
-    minimum: 0
-    maximum: 1
+    items:
+      minimum: 0
+      maximum: 1
 
   dc-gpios:
     maxItems: 1

Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml

@@ -37,7 +37,15 @@ properties:
     maximum: 102040816
 
   spi-rx-bus-width:
-    enum: [1, 2, 4]
+    maxItems: 2
+    # all lanes must have the same width
+    oneOf:
+      - contains:
+          const: 1
+      - contains:
+          const: 2
+      - contains:
+          const: 4
 
   vdd-5v-supply: true
   vdd-1v8-supply: true
@@ -88,6 +96,18 @@ oneOf:
 
 unevaluatedProperties: false
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          enum:
+            - adi,ad4030-24
+            - adi,ad4032-24
+    then:
+      properties:
+        spi-rx-bus-width:
+          maxItems: 1
+
 examples:
   - |
     #include <dt-bindings/gpio/gpio.h>
@@ -108,3 +128,23 @@ examples:
             reset-gpios = <&gpio0 1 GPIO_ACTIVE_LOW>;
         };
     };
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "adi,ad4630-24";
+            reg = <0>;
+            spi-max-frequency = <80000000>;
+            spi-rx-bus-width = <4>, <4>;
+            vdd-5v-supply = <&supply_5V>;
+            vdd-1v8-supply = <&supply_1_8V>;
+            vio-supply = <&supply_1_8V>;
+            ref-supply = <&supply_5V>;
+            cnv-gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
+            reset-gpios = <&gpio0 1 GPIO_ACTIVE_LOW>;
+        };
+    };

Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml

@@ -38,8 +38,9 @@ properties:
   spi-cpha: true
 
   spi-rx-bus-width:
-    minimum: 1
-    maximum: 4
+    items:
+      minimum: 1
+      maximum: 4
 
   avdd-supply:
     description: Analog power supply.

Documentation/devicetree/bindings/spi/adi,axi-spi-engine.yaml

@@ -70,6 +70,21 @@ required:
 
 unevaluatedProperties: false
 
+patternProperties:
+  "^.*@[0-9a-f]+":
+    type: object
+
+    properties:
+      spi-rx-bus-width:
+        maxItems: 8
+        items:
+          enum: [0, 1]
+
+      spi-tx-bus-width:
+        maxItems: 8
+        items:
+          enum: [0, 1]
+
 examples:
   - |
     spi@44a00000 {

Documentation/devicetree/bindings/spi/allwinner,sun4i-a10-spi.yaml

@@ -55,10 +55,12 @@ patternProperties:
           maximum: 4
 
       spi-rx-bus-width:
-        const: 1
+        items:
+          - const: 1
 
       spi-tx-bus-width:
-        const: 1
+        items:
+          - const: 1
 
 required:
   - compatible

Documentation/devicetree/bindings/spi/allwinner,sun6i-a31-spi.yaml

@@ -81,10 +81,12 @@ patternProperties:
           maximum: 4
 
       spi-rx-bus-width:
-        const: 1
+        items:
+          - const: 1
 
       spi-tx-bus-width:
-        const: 1
+        items:
+          - const: 1
 
 required:
   - compatible

Documentation/devicetree/bindings/spi/andestech,ae350-spi.yaml

@@ -45,10 +45,12 @@ patternProperties:
 
     properties:
       spi-rx-bus-width:
-        enum: [1, 4]
+        items:
+          - enum: [1, 4]
 
       spi-tx-bus-width:
-        enum: [1, 4]
+        items:
+          - enum: [1, 4]
 
 allOf:
   - $ref: spi-controller.yaml#

Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml

@@ -54,10 +54,12 @@ patternProperties:
 
     properties:
       spi-rx-bus-width:
-        enum: [1, 2, 4]
+        items:
+          - enum: [1, 2, 4]
 
       spi-tx-bus-width:
-        enum: [1, 2, 4]
+        items:
+          - enum: [1, 2, 4]
 
 required:
   - compatible

Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml

@@ -64,9 +64,23 @@ properties:
     description:
       Bus width to the SPI bus used for read transfers.
       If 0 is provided, then no RX will be possible on this device.
-    $ref: /schemas/types.yaml#/definitions/uint32
-    enum: [0, 1, 2, 4, 8]
-    default: 1
+
+      Some SPI peripherals and controllers may have multiple data lanes for
+      receiving two or more words at the same time. If this is the case, each
+      index in the array represents the lane on both the SPI peripheral and
+      controller. Additional mapping properties may be needed if a lane is
+      skipped on either side.
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    items:
+      enum: [0, 1, 2, 4, 8]
+    default: [1]
+
+  spi-rx-lane-map:
+    description: Mapping of peripheral SDO lanes to controller SDI lanes.
+      Each index in the array represents a peripheral SDO lane, and the value
+      at that index represents the corresponding controller SDI lane.
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    default: [0, 1, 2, 3, 4, 5, 6, 7]
 
   spi-rx-delay-us:
     description:
@@ -81,9 +95,23 @@ properties:
     description:
       Bus width to the SPI bus used for write transfers.
       If 0 is provided, then no TX will be possible on this device.
-    $ref: /schemas/types.yaml#/definitions/uint32
-    enum: [0, 1, 2, 4, 8]
-    default: 1
+
+      Some SPI peripherals and controllers may have multiple data lanes for
+      transmitting two or more words at the same time. If this is the case, each
+      index in the array represents the lane on both the SPI peripheral and
+      controller. Additional mapping properties may be needed if a lane is
+      skipped on either side.
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    items:
+      enum: [0, 1, 2, 4, 8]
+    default: [1]
+
+  spi-tx-lane-map:
+    description: Mapping of peripheral SDI lanes to controller SDO lanes.
+      Each index in the array represents a peripheral SDI lane, and the value
+      at that index represents the corresponding controller SDO lane.
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    default: [0, 1, 2, 3, 4, 5, 6, 7]
 
   spi-tx-delay-us:
     description:

Documentation/spi/index.rst

@@ -9,6 +9,7 @@ Serial Peripheral Interface (SPI)
 
    spi-summary
    spidev
+   multiple-data-lanes
    butterfly
    spi-lm70llp
    spi-sc18is602