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[98.183.112.25]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-708f60a55e1sm1719911a34.11.2024.07.22.15.01.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jul 2024 15:01:25 -0700 (PDT) From: David Lechner To: Mark Brown , Jonathan Cameron , Rob Herring , Krzysztof Kozlowski , Conor Dooley , =?utf-8?q?Nuno_S=C3=A1?= Cc: David Lechner , Michael Hennerich , Lars-Peter Clausen , David Jander , Martin Sperl , linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org Subject: [PATCH RFC v3 0/9] spi: axi-spi-engine: add offload support Date: Mon, 22 Jul 2024 16:57:07 -0500 Message-ID: <20240722-dlech-mainline-spi-engine-offload-2-v3-0-7420e45df69b@baylibre.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-spi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mailer: b4 0.14.0 There is a recap at the end of this cover letter for those not familiar with the previous discussions. For those that are, we'll get right to the changes since the last version. In RFC v2, most of the discussion was around the DT bindings, so that is what has mostly changed since then. I think we mostly settled on what properties are needed and where they should go. There are probably still some details to work out (see PATCH 5/9 for more discussion) but I think we have the big-picture stuff figured out. Here is the actual devicetree used for testing to show how it all comes together: trigger_clk: adc-trigger-clock { compatible = "pwm-clock"; #clock-cells = <0>; #trigger-source-cells = <0>; pwms = <&adc_trigger 0 10000>; }; ... axi_spi_engine_0: spi@44a00000 { compatible = "adi,axi-spi-engine-1.00.a"; reg = <0x44a00000 0x1000>; interrupt-parent = <&intc>; interrupts = <0 56 IRQ_TYPE_LEVEL_HIGH>; clocks = <&clkc 15>, <&spi_clk>; clock-names = "s_axi_aclk", "spi_clk"; /* offload-specific properties */ #spi-offload-cells = <1>; dmas = <&rx_dma 0>; dma-names = "offload0-rx"; trigger-sources = <&trigger_clk>; #address-cells = <1>; #size-cells = <0>; ad7986: adc@0 { compatible = "adi,ad7986"; reg = <0>; spi-max-frequency = <111111111>; /* 9 ns period */ adi,spi-mode = "single"; avdd-supply = <&eval_u12>; dvdd-supply = <&eval_u12>; vio-supply = <&eval_u3>; bvdd-supply = <&eval_u10>; ref-supply = <&eval_u5>; turbo-gpios = <&gpio0 87 GPIO_ACTIVE_HIGH>; spi-offloads = <&axi_spi_engine_0 0>; }; }; A working branch complete with extra hacks can be found at [1]. Also, I took a detour looking into what it would take to get Martin Sperl's Raspberry Pi DMA offload proof-of-concept [2] updated to work with this. This way we could have a second user to help guide the design process. Given all of the SPI hardware quirks on that platform and the unsolved technical issues, like how to get accurate time delays and how to work around the 32-bit DMA word limitation, it would be more work than I have time for (at least without someone sponsoring the work). [1]: https://github.com/dlech/linux/tree/axi-spi-engine-offload-v3 [2]: https://github.com/msperl/spi-bcm2835/blob/refactor_dmachain_for_prepared_messages/spi-bcm2835dma.c --- Changes in v3: - See individual patches for more detailed changes. - Reworked DT bindings to have things physically connected to the SPI controller be properties of the SPI controller and use more conventional provider/consumer properties. - Added more SPI APIs for peripheral drivers to use to get auxillary offload resources, like triggers. - Link to v2: https://lore.kernel.org/r/20240510-dlech-mainline-spi-engine-offload-2-v2-0-8707a870c435@baylibre.com --- 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 < < < | | +---------------------+ | | | +-------------------------------+ To: Mark Brown To: Jonathan Cameron To: Rob Herring To: Krzysztof Kozlowski To: Conor Dooley To: Nuno Sá Cc: Michael Hennerich Cc: Lars-Peter Clausen Cc: David Jander Cc: Martin Sperl Cc: Cc: Cc: Cc: --- David Lechner (9): spi: dt-bindings: add spi-offload properties spi: add basic support for SPI offloading spi: add support for hardware triggered offload spi: add offload TX/RX streaming APIs spi: dt-bindings: axi-spi-engine: document spi-offloads spi: axi-spi-engine: implement offload support iio: buffer-dmaengine: generalize requesting DMA channel dt-bindings: iio: adc: adi,ad7944: add SPI offload properties iio: adc: ad7944: add support for SPI offload .../devicetree/bindings/iio/adc/adi,ad7944.yaml | 3 + .../bindings/spi/adi,axi-spi-engine.yaml | 41 +++ .../devicetree/bindings/spi/spi-controller.yaml | 5 + .../bindings/spi/spi-peripheral-props.yaml | 11 + drivers/iio/adc/ad7944.c | 173 ++++++++++- drivers/iio/buffer/industrialio-buffer-dmaengine.c | 39 ++- drivers/iio/dac/adi-axi-dac.c | 3 +- drivers/spi/spi-axi-spi-engine.c | 341 ++++++++++++++++++++- drivers/spi/spi.c | 226 +++++++++++++- include/linux/iio/buffer-dmaengine.h | 11 +- include/linux/spi/spi.h | 169 ++++++++++ 11 files changed, 989 insertions(+), 33 deletions(-) --- base-commit: 7a891f6a5000f7658274b554cf993dd56aa5adbc change-id: 20240510-dlech-mainline-spi-engine-offload-2-afce3790b5ab