Re: [PATCH 2/3] dmaengine: sun6i: Add support for Allwinner A23 (sun8i) variant

On Sat, Sep 13, 2014 at 09:53:00PM +0800, Chen-Yu Tsai wrote:

The BSP I have has this:

static void sunxi_dma_hw_init(struct sunxi_dmadev *dev)
{
        struct sunxi_dmadev *sunxi_dev = dev;

        clk_prepare_enable(sunxi_dev->ahb_clk);
#ifdef CONFIG_ARCH_SUN8IW3
        writel(0x04, sunxi_dev->base + DMA_GATE);
#endif
}

/* All is ok, and open the clock */
sunxi_dma_hw_init(sunxi_dev);

So I guess we can say that it's not that undocumented :)

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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On Tue, Sep 16, 2014 at 6:35 PM, Maxime Ripard
[off-list ref] wrote:

On Sat, Sep 13, 2014 at 09:53:00PM +0800, Chen-Yu Tsai wrote:

quoted

The A23 SoC has the same dma engine as the A31 (sun6i), with a
reduced amount of endpoints and physical channels. Add the proper
config data and compatible string to support it.

A slight difference in sun8i is an undocumented register needs
to be toggled for dma to function.

Signed-off-by: Chen-Yu Tsai <redacted>
---
 Documentation/devicetree/bindings/dma/sun6i-dma.txt |  2 +-
 drivers/dma/Kconfig                                 |  4 ++--
 drivers/dma/sun6i-dma.c                             | 20 ++++++++++++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/dma/sun6i-dma.txt b/Documentation/devicetree/bindings/dma/sun6i-dma.txt
index 3e145c1..9cdcba24d 100644
--- a/Documentation/devicetree/bindings/dma/sun6i-dma.txt
+++ b/Documentation/devicetree/bindings/dma/sun6i-dma.txt

@@ -4,7 +4,7 @@ This driver follows the generic DMA bindings defined in dma.txt.

 Required properties:

-- compatible:        Must be "allwinner,sun6i-a31-dma"
+- compatible:        Must be "allwinner,sun6i-a31-dma" or "allwinner,sun8i-a23-dma"
 - reg:               Should contain the registers base address and length
 - interrupts:        Should contain a reference to the interrupt used by this device
 - clocks:    Should contain a reference to the parent AHB clock

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 9b1ea0e..5361aa7 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig

@@ -395,12 +395,12 @@ config XILINX_VDMA

 config DMA_SUN6I
      tristate "Allwinner A31 SoCs DMA support"
-     depends on MACH_SUN6I || COMPILE_TEST
+     depends on MACH_SUN6I || MACH_SUN8I || COMPILE_TEST
      depends on RESET_CONTROLLER
      select DMA_ENGINE
      select DMA_VIRTUAL_CHANNELS
      help
-       Support for the DMA engine for Allwinner A31 SoCs.
+       Support for the DMA engine first found in Allwinner A31 SoCs.

 config NBPFAXI_DMA
      tristate "Renesas Type-AXI NBPF DMA support"

diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
index 89ca0c4..29667dd 100644
--- a/drivers/dma/sun6i-dma.c
+++ b/drivers/dma/sun6i-dma.c

@@ -878,8 +878,20 @@ static struct sun6i_dma_config sun6i_a31_dma_cfg = {
      .nr_max_vchans   = 53,
 };

+/*
+ * The A23 only has 8 physical channels, a maximum DRQ port id of 24,
+ * and a total of 37 usable source and destination endpoints.
+ */
+
+static struct sun6i_dma_config sun8i_a23_dma_cfg = {
+     .nr_max_channels = 8,
+     .nr_max_requests = 24,
+     .nr_max_vchans   = 37,
+};
+
 static struct of_device_id sun6i_dma_match[] = {
      { .compatible = "allwinner,sun6i-a31-dma", .data = &sun6i_a31_dma_cfg },
+     { .compatible = "allwinner,sun8i-a23-dma", .data = &sun8i_a23_dma_cfg },
      { /* sentinel */ }
 };

@@ -1008,6 +1020,14 @@ static int sun6i_dma_probe(struct platform_device *pdev)
              goto err_dma_unregister;
      }

+     /*
+      * sun8i variant requires us to toggle an undocumented register,
+      * as seen in Allwinner's SDK.

The BSP I have has this:

static void sunxi_dma_hw_init(struct sunxi_dmadev *dev)
{
        struct sunxi_dmadev *sunxi_dev = dev;

        clk_prepare_enable(sunxi_dev->ahb_clk);
#ifdef CONFIG_ARCH_SUN8IW3
        writel(0x04, sunxi_dev->base + DMA_GATE);
#endif
}

/* All is ok, and open the clock */
sunxi_dma_hw_init(sunxi_dev);

So I guess we can say that it's not that undocumented :)

That's right. I meant undocumented in the user manual.
I did reference the SDK in the comment, didn't I? :)

ChenYu