spi: axi-spi-engine: add offload support

Merge series from David Lechner <[email protected]>:

As a recap, here is the background and end goal of this series:

The AXI SPI Engine is a SPI controller that has the ability to record a
series of SPI transactions and then play them back using a hardware
trigger. This allows operations to be performed, repeating many times,
without any CPU intervention. This is needed for achieving high data
rates (millions of samples per second) from ADCs and DACs that are
connected via a SPI bus.

The offload hardware interface consists of a trigger input and a data
output for the RX data. These are connected to other hardware external
to the SPI controller.

To record one or more transactions, commands and TX data are written
to memories in the controller (RX buffer is not used since RX data gets
streamed to an external sink). This sequence of transactions can then be
played back when the trigger input is asserted.

This series includes core SPI support along with the first SPI
controller (AXI SPI Engine) and SPI peripheral (AD7944 ADC) that use
them. This enables capturing analog data at 2 million samples per
second.

The hardware setup looks like this:

+-------------------------------+   +------------------+
|                               |   |                  |
|  SOC/FPGA                     |   |  AD7944 ADC      |
|  +---------------------+      |   |                  |
|  | AXI SPI Engine      |      |   |                  |
|  |             SPI Bus ============ SPI Bus          |
|  |                     |      |   |                  |
|  |  +---------------+  |      |   |                  |
|  |  | Offload 0     |  |      |   +------------------+
|  |  |   RX DATA OUT > > > >   |
|  |  |    TRIGGER IN < < <  v  |
|  |  +---------------+  | ^ v  |
|  +---------------------+ ^ v  |
|  | AXI PWM             | ^ v  |
|  |                 CH0 > ^ v  |
|  +---------------------+   v  |
|  | AXI DMA             |   v  |
|  |                 CH0 < < <  |
|  +---------------------+      |
|                               |
+-------------------------------+

Author: broonie

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

@@ -41,6 +41,26 @@ properties:
       - const: s_axi_aclk
       - const: spi_clk
 
+  trigger-sources:
+    description:
+      An array of trigger source phandles for offload instances. The index in
+      the array corresponds to the offload instance number.
+    minItems: 1
+    maxItems: 32
+
+  dmas:
+    description:
+      DMA channels connected to the input or output stream interface of an
+      offload instance.
+    minItems: 1
+    maxItems: 32
+
+  dma-names:
+    items:
+      pattern: "^offload(?:[12]?[0-9]|3[01])-[tr]x$"
+    minItems: 1
+    maxItems: 32
+
 required:
   - compatible
   - reg
@@ -59,6 +79,10 @@ examples:
         clocks = <&clkc 15>, <&clkc 15>;
         clock-names = "s_axi_aclk", "spi_clk";
 
+        trigger-sources = <&trigger_clock>;
+        dmas = <&dma 0>;
+        dma-names = "offload0-rx";
+
         #address-cells = <1>;
         #size-cells = <0>;
 

Documentation/devicetree/bindings/trigger-source/pwm-trigger.yaml

@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/trigger-source/pwm-trigger.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic trigger source using PWM
+
+description: Remaps a PWM channel as a trigger source.
+
+maintainers:
+  - David Lechner <[email protected]>
+
+properties:
+  compatible:
+    const: pwm-trigger
+
+  '#trigger-source-cells':
+    const: 0
+
+  pwms:
+    maxItems: 1
+
+required:
+  - compatible
+  - '#trigger-source-cells'
+  - pwms
+
+additionalProperties: false
+
+examples:
+  - |
+    trigger {
+        compatible = "pwm-trigger";
+        #trigger-source-cells = <0>;
+        pwms = <&pwm 0 1000000 0>;
+    };

MAINTAINERS

@@ -22295,6 +22295,13 @@ F:	Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
 F:	drivers/mtd/spi-nor/
 F:	include/linux/mtd/spi-nor.h
 
+SPI OFFLOAD
+R:	David Lechner <[email protected]>
+F:	drivers/spi/spi-offload-trigger-pwm.c
+F:	drivers/spi/spi-offload.c
+F:	include/linux/spi/spi-offload.h
+K:	spi_offload
+
 SPI SUBSYSTEM
 M:	Mark Brown <[email protected]>
 L:	[email protected]
@@ -24050,6 +24057,11 @@ W:	https://github.com/srcres258/linux-doc
 T:	git git://github.com/srcres258/linux-doc.git doc-zh-tw
 F:	Documentation/translations/zh_TW/
 
+TRIGGER SOURCE - PWM
+M:	David Lechner <[email protected]>
+S:	Maintained
+F:	Documentation/devicetree/bindings/trigger-source/pwm-trigger.yaml
+
 TRUSTED SECURITY MODULE (TSM) ATTESTATION REPORTS
 M:	Dan Williams <[email protected]>
 L:	[email protected]

drivers/spi/Kconfig

@@ -55,6 +55,9 @@ config SPI_MEM
 	  This extension is meant to simplify interaction with SPI memories
 	  by providing a high-level interface to send memory-like commands.
 
+config SPI_OFFLOAD
+	bool
+
 comment "SPI Master Controller Drivers"
 
 config SPI_AIROHA_SNFI
@@ -176,6 +179,7 @@ config SPI_AU1550
 config SPI_AXI_SPI_ENGINE
 	tristate "Analog Devices AXI SPI Engine controller"
 	depends on HAS_IOMEM
+	select SPI_OFFLOAD
 	help
 	  This enables support for the Analog Devices AXI SPI Engine SPI controller.
 	  It is part of the SPI Engine framework that is used in some Analog Devices
@@ -1317,4 +1321,16 @@ endif # SPI_SLAVE
 config SPI_DYNAMIC
 	def_bool ACPI || OF_DYNAMIC || SPI_SLAVE
 
+if SPI_OFFLOAD
+
+comment "SPI Offload triggers"
+
+config SPI_OFFLOAD_TRIGGER_PWM
+	tristate "SPI offload trigger using PWM"
+	depends on PWM
+	help
+	  Generic SPI offload trigger implemented using PWM output.
+
+endif # SPI_OFFLOAD
+
 endif # SPI

drivers/spi/Makefile

@@ -10,6 +10,7 @@ ccflags-$(CONFIG_SPI_DEBUG) := -DDEBUG
 obj-$(CONFIG_SPI_MASTER)		+= spi.o
 obj-$(CONFIG_SPI_MEM)			+= spi-mem.o
 obj-$(CONFIG_SPI_MUX)			+= spi-mux.o
+obj-$(CONFIG_SPI_OFFLOAD)		+= spi-offload.o
 obj-$(CONFIG_SPI_SPIDEV)		+= spidev.o
 obj-$(CONFIG_SPI_LOOPBACK_TEST)		+= spi-loopback-test.o
 
@@ -163,3 +164,6 @@ obj-$(CONFIG_SPI_AMD)			+= spi-amd.o
 # SPI slave protocol handlers
 obj-$(CONFIG_SPI_SLAVE_TIME)		+= spi-slave-time.o
 obj-$(CONFIG_SPI_SLAVE_SYSTEM_CONTROL)	+= spi-slave-system-control.o
+
+# SPI offload triggers
+obj-$(CONFIG_SPI_OFFLOAD_TRIGGER_PWM)	+= spi-offload-trigger-pwm.o