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[RFC,0/6] Allow DMA consumers to pass a cookie to providers' of_xlate

Message ID 20250730-topic-dma_genise_cookie-v1-0-b505c1238f9f@oss.qualcomm.com (mailing list archive)
Headers
Series Allow DMA consumers to pass a cookie to providers' of_xlate |

Message

Konrad Dybcio July 30, 2025, 9:33 a.m. UTC 
The DMA subsystem attempts to make it theoretically possible to pair
any DMA block with any user. While that's convenient from a
codebase sanity perspective, some blocks are more intertwined.

One such case is the Qualcomm GENI, where each wrapper contains a
number of Serial Engine instances, each one of which can be programmed
to support a different protocol (such as I2C, I3C, SPI, UART, etc.).

The GPI DMA it's designed together with, needs to receive the ID of the
protocol that's in use, to adjust its behavior accordingly. Currently,
that's done through passing that ID through device tree, with each
Serial Engine expressed NUM_PROTOCOL times, resulting in terrible
dt-bindings that are full of useless copypasta.

Currently, the DT looks like:

i2c@foobar {
	compatible = "qcom,geni-i2c";
	dmas = <&gpi_dma1 0 0 QCOM_GPI_I2C>,
	       <&gpi_dma1 1 0 QCOM_GPI_I2C>;
	// actual hw description
};

spi@foobar {
        compatible = "qcom,geni-spi";
        dmas = <&gpi_dma1 0 1 QCOM_GPI_SPI>,
               <&gpi_dma1 1 1 QCOM_GPI_SPI>;
	// actual, identical hw description
};

Which is manageable when there's two of them. Unfortunately, we're
in the double digits range nowadays.

This series attempts to cut down on that through making the last cell
unnecessary, moving the purely-SW data that the current protocol ID is
into the driver.

The mass of_xlate signature change is a little unfortunate, let me know
if it can be avoided somehow..

Attaching the relevant dt-bindings change and converting one platform
over as an example.

Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
---
Konrad Dybcio (6):
      dt-bindings: dma: qcom,gpi: Retire passing the protocol ID
      dmaengine: Make of_dma_request_slave_channel pass a cookie to of_xlate
      dmaengine: qcom: gpi: Accept protocol ID hints
      i2c: qcom-geni: Hint GENI protocol ID to GPI DMA
      spi: geni-qcom: Hint GENI protocol ID to GPI DMA
      arm64: dts: qcom: x1e80100: Remove GENI protocol ID from DMA cells

 .../devicetree/bindings/dma/qcom,gpi.yaml          |   5 +-
 arch/arm64/boot/dts/qcom/x1e80100.dtsi             | 198 ++++++++++-----------
 drivers/dma/amba-pl08x.c                           |   3 +-
 drivers/dma/apple-admac.c                          |   3 +-
 drivers/dma/at_hdmac.c                             |   6 +-
 drivers/dma/at_xdmac.c                             |   3 +-
 drivers/dma/bcm2835-dma.c                          |   3 +-
 drivers/dma/dma-jz4780.c                           |   3 +-
 drivers/dma/dmaengine.c                            |  20 ++-
 drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c     |   3 +-
 drivers/dma/dw/of.c                                |   3 +-
 drivers/dma/ep93xx_dma.c                           |   6 +-
 drivers/dma/fsl-edma-main.c                        |   6 +-
 drivers/dma/img-mdc-dma.c                          |   3 +-
 drivers/dma/imx-dma.c                              |   3 +-
 drivers/dma/imx-sdma.c                             |   3 +-
 drivers/dma/lgm/lgm-dma.c                          |   3 +-
 drivers/dma/milbeaut-hdmac.c                       |   4 +-
 drivers/dma/mmp_pdma.c                             |   3 +-
 drivers/dma/mmp_tdma.c                             |   3 +-
 drivers/dma/moxart-dma.c                           |   3 +-
 drivers/dma/mxs-dma.c                              |   3 +-
 drivers/dma/nbpfaxi.c                              |   3 +-
 drivers/dma/of-dma.c                               |  18 +-
 drivers/dma/owl-dma.c                              |   3 +-
 drivers/dma/pl330.c                                |   3 +-
 drivers/dma/pxa_dma.c                              |   3 +-
 drivers/dma/qcom/bam_dma.c                         |   3 +-
 drivers/dma/qcom/gpi.c                             |  16 +-
 drivers/dma/qcom/qcom_adm.c                        |   3 +-
 drivers/dma/sh/rcar-dmac.c                         |   3 +-
 drivers/dma/sh/rz-dmac.c                           |   3 +-
 drivers/dma/sh/usb-dmac.c                          |   3 +-
 drivers/dma/st_fdma.c                              |   3 +-
 drivers/dma/ste_dma40.c                            |   3 +-
 drivers/dma/stm32/stm32-dma.c                      |   3 +-
 drivers/dma/stm32/stm32-dma3.c                     |   4 +-
 drivers/dma/stm32/stm32-mdma.c                     |   3 +-
 drivers/dma/sun4i-dma.c                            |   3 +-
 drivers/dma/sun6i-dma.c                            |   3 +-
 drivers/dma/tegra186-gpc-dma.c                     |   3 +-
 drivers/dma/tegra20-apb-dma.c                      |   3 +-
 drivers/dma/tegra210-adma.c                        |   3 +-
 drivers/dma/ti/cppi41.c                            |   3 +-
 drivers/dma/ti/edma.c                              |   3 +-
 drivers/dma/ti/k3-udma.c                           |   3 +-
 drivers/dma/uniphier-xdmac.c                       |   3 +-
 drivers/dma/xilinx/xilinx_dma.c                    |   3 +-
 drivers/dma/xilinx/xilinx_dpdma.c                  |   3 +-
 drivers/dma/xilinx/zynqmp_dma.c                    |   3 +-
 drivers/i2c/busses/i2c-qcom-geni.c                 |   4 +-
 drivers/spi/spi-geni-qcom.c                        |   4 +-
 include/linux/dmaengine.h                          |   7 +
 include/linux/of_dma.h                             |  16 +-
 sound/soc/apple/mca.c                              |   2 +-
 sound/soc/renesas/rcar/dma.c                       |   2 +-
 56 files changed, 261 insertions(+), 177 deletions(-)
---
base-commit: 79fb37f39b77bbf9a56304e9af843cd93a7a1916
change-id: 20250714-topic-dma_genise_cookie-66dcb07f3fd9

Best regards,