From: "Martin Povišer" <povik+lin@cutebit.org>
To: "Martin Povišer" <povik+lin@cutebit.org>,
"Vinod Koul" <vkoul@kernel.org>,
"Rob Herring" <robh+dt@kernel.org>,
"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
"Conor Dooley" <conor+dt@kernel.org>
Cc: asahi@lists.linux.dev, dmaengine@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
Rob Herring <robh@kernel.org>
Subject: [PATCH v3 1/2] dt-bindings: dma: apple,sio: Add schema
Date: Fri, 13 Oct 2023 18:49:35 +0200 [thread overview]
Message-ID: <20231013164936.60718-2-povik+lin@cutebit.org> (raw)
In-Reply-To: <20231013164936.60718-1-povik+lin@cutebit.org>
Describe the SIO coprocessor which serves as pretend DMA controller on
recent Apple platforms.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
---
This patch was reviewed outside the version count here.
https://lore.kernel.org/asahi/167693643966.613996.10372170526471864080.robh@kernel.org
.../devicetree/bindings/dma/apple,sio.yaml | 111 ++++++++++++++++++
1 file changed, 111 insertions(+)
create mode 100644 Documentation/devicetree/bindings/dma/apple,sio.yaml
diff --git a/Documentation/devicetree/bindings/dma/apple,sio.yaml b/Documentation/devicetree/bindings/dma/apple,sio.yaml
new file mode 100644
index 000000000000..0e3780ad9dd7
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/apple,sio.yaml
@@ -0,0 +1,111 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/dma/apple,sio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple SIO Coprocessor
+
+description:
+ SIO is a coprocessor on Apple M1 and later chips (and maybe also on earlier
+ chips). Its role is to offload SPI, UART and DisplayPort audio transfers,
+ being a pretend DMA controller.
+
+maintainers:
+ - Martin Povišer <povik+lin@cutebit.org>
+
+allOf:
+ - $ref: dma-controller.yaml#
+
+properties:
+ compatible:
+ items:
+ - enum:
+ - apple,t6000-sio
+ - apple,t8103-sio
+ - const: apple,sio
+
+ reg:
+ maxItems: 1
+
+ '#dma-cells':
+ const: 1
+ description:
+ DMA clients specify a single cell that corresponds to the RTKit endpoint
+ number used for arranging the transfers in question
+
+ dma-channels:
+ maximum: 128
+
+ mboxes:
+ maxItems: 1
+
+ iommus:
+ maxItems: 1
+
+ power-domains:
+ maxItems: 1
+
+ memory-region:
+ minItems: 2
+ maxItems: 8
+ description:
+ A number of references to reserved memory regions among which are the DATA/TEXT
+ sections of coprocessor executable firmware and also auxiliary firmware data
+ describing the available DMA-enabled peripherals
+
+ apple,sio-firmware-params:
+ $ref: /schemas/types.yaml#/definitions/uint32-array
+ description: |
+ Parameters in the form of opaque key/value pairs that are to be sent to the SIO
+ coprocesssor once it boots. These parameters can point into the reserved memory
+ regions (in device address space).
+
+ Note that unlike Apple's firmware, we treat the parameters, and the data they
+ refer to, as opaque. Apple embed short data blobs into their SIO devicetree node
+ that describe the DMA-enabled peripherals (presumably with defined semantics).
+ Their driver processes those blobs and sets up data structure in mapped device
+ memory, then references this memory in the parameters sent to the SIO. At the
+ level of description we are opting for in this binding, we assume the job of
+ constructing those data structures has been done in advance, leaving behind an
+ opaque list of key/value parameter pairs to be sent by a prospective driver.
+
+ This approach is chosen for two reasons:
+
+ - It means we don't need to try to understand the semantics of Apple's blobs
+ as long as we know the transformation we need to do from Apple's devicetree
+ data to SIO data (which can be shoved away into a loader). It also means the
+ semantics of Apple's blobs (or of something to replace them) need not be part
+ of the binding and be kept up with Apple's firmware changes in the future.
+
+ - It leaves less work for the driver attaching on this binding. Instead the work
+ is done upfront in the loader which can be better suited for keeping up with
+ Apple's firmware changes.
+
+required:
+ - compatible
+ - reg
+ - '#dma-cells'
+ - dma-channels
+ - mboxes
+ - iommus
+ - power-domains
+
+additionalProperties: false
+
+examples:
+ - |
+ sio: dma-controller@36400000 {
+ compatible = "apple,t8103-sio", "apple,sio";
+ reg = <0x36400000 0x8000>;
+ dma-channels = <128>;
+ #dma-cells = <1>;
+ mboxes = <&sio_mbox>;
+ iommus = <&sio_dart 0>;
+ power-domains = <&ps_sio_cpu>;
+ memory-region = <&sio_text>, <&sio_data>,
+ <&sio_auxdata1>, <&sio_auxdata2>; /* Filled by loader */
+ apple,sio-firmware-params = <0xb 0x10>, <0xc 0x1b80>, <0xf 0x14>,
+ <0x10 0x1e000>, <0x30d 0x34>, <0x30e 0x4000>,
+ <0x1a 0x38>, <0x1b 0x50>; /* Filled by loader */
+ };
--
2.38.3
next prev parent reply other threads:[~2023-10-13 16:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-13 16:49 [PATCH v3 0/2] Apple SIO driver Martin Povišer
2023-10-13 16:49 ` Martin Povišer [this message]
2023-10-13 16:49 ` [PATCH v3 2/2] dmaengine: apple-sio: Add " Martin Povišer
2023-10-16 7:11 ` Vinod Koul
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