[PATCH 29/30] dt-bindings: spi: dw: Add Baikal-T1 SPI Controllers

[Serge Semin <Sergey.Semin@baikalelectronics.ru>]

These controllers are based on the DW APB SSI IP-core and embedded into
the SoC, so two of them are equipped with IRQ, DMA, 64 words FIFOs and 4
native CS, while another one as being utilized by the Baikal-T1 System
Boot Controller has got a very limited resources: no IRQ, no DMA, only a
single native chip-select and just 8 bytes Tx/Rx FIFOs available. That's
why we have to mark the IRQ to be optional for the later interface.

The SPI controller embedded into the Baikal-T1 System Boot Controller can
be also used to directly access an external SPI flash by means of a
dedicated FSM. The corresponding MMIO region availability is switchable by
the embedded multiplexor, which phandle can be specified in the dts node.

* We added a new example to test out the non-standard Baikal-T1 System
Boot SPI Controller DT binding.

Co-developed-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
---
 .../bindings/spi/snps,dw-apb-ssi.yaml         | 33 +++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
index c62cbe79f00d..d6ae35777dac 100644
--- a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
+++ b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
@@ -22,6 +22,21 @@ allOf:
       properties:
         reg:
           minItems: 2
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - baikal,bt1-sys-ssi
+    then:
+      properties:
+        mux-controls:
+          maxItems: 1
+      required:
+        - mux-controls
+    else:
+      required:
+        - interrupts
 
 properties:
   compatible:
@@ -44,12 +59,16 @@ properties:
           - const: snps,dw-apb-ssi
       - description: Intel Keem Bay SPI Controller
         const: intel,keembay-ssi
+      - description: Baikal-T1 SPI Controller
+        const: baikal,bt1-ssi
+      - description: Baikal-T1 System Boot SPI Controller
+        const: baikal,bt1-sys-ssi
 
   reg:
     minItems: 1
     items:
       - description: DW APB SSI controller memory mapped registers
-      - description: SPI MST region map
+      - description: SPI MST region map or directly mapped SPI ROM
 
   interrupts:
     maxItems: 1
@@ -114,7 +133,6 @@ required:
   - reg
   - "#address-cells"
   - "#size-cells"
-  - interrupts
   - clocks
 
 examples:
@@ -130,4 +148,15 @@ examples:
       cs-gpios = <&gpio0 13 0>,
                  <&gpio0 14 0>;
     };
+  - |
+    spi@1f040100 {
+      compatible = "baikal,bt1-sys-ssi";
+      reg = <0x1f040100 0x900>,
+            <0x1c000000 0x1000000>;
+      #address-cells = <1>;
+      #size-cells = <0>;
+      mux-controls = <&boot_mux>;
+      clocks = <&ccu_sys>;
+      clock-names = "ssi_clk";
+    };
 ...
-- 
2.27.0