spi: pl022: use generic DMA slave configuration if possible

With the new OF DMA binding, it is possible to completely avoid the
need for platform_data for configuring a DMA channel. In cases where the
platform has already been converted, calling dma_request_slave_channel
should get all the necessary information from the device tree.

Like the patch that converts the dw_dma controller, this is completely
untested and is looking for someone to try it out.

Signed-off-by: Arnd Bergmann <[e-mail]>
Acked-by: Grant Likely <[e-mail]>
Acked-by: Mark Brown <[e-mail]>
Acked-by: Linus Walleij <[e-mail]>
Cc: [e-mail]
Cc: Viresh Kumar <[e-mail]>
Cc: Andy Shevchenko <[e-mail]>
Cc: Vinod Koul <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]

Documentation/devicetree/bindings/spi/spi_pl022.txt

···
                             device will be suspended immediately
 - pl022,rt : indicates the controller should run the message pump with realtime
              priority to minimise the transfer latency on the bus (boolean)
+- dmas : Two or more DMA channel specifiers following the convention outlined
+         in bindings/dma/dma.txt
+- dma-names: Names for the dma channels, if present. There must be at
+	     least one channel named "tx" for transmit and named "rx" for
+             receive.
 
 
 SPI slave nodes must be children of the SPI master node and can
···
 - pl022,wait-state : Microwire interface: Wait state
 - pl022,duplex : Microwire interface: Full/Half duplex
 
+
+Example:
+
+	spi@e0100000 {
+		compatible = "arm,pl022", "arm,primecell";
+		reg = <0xe0100000 0x1000>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		interrupts = <0 31 0x4>;
+		dmas = <&dma-controller 23 1>,
+			<&dma-controller 24 0>;
+		dma-names = "rx", "tx";
+
+		m25p80@1 {
+			compatible = "st,m25p80";
+			reg = <1>;
+			spi-max-frequency = <12000000>;
+			spi-cpol;
+			spi-cpha;
+			pl022,hierarchy = <0>;
+			pl022,interface = <0>;
+			pl022,slave-tx-disable;
+			pl022,com-mode = <0x2>;
+			pl022,rx-level-trig = <0>;
+			pl022,tx-level-trig = <0>;
+			pl022,ctrl-len = <0x11>;
+			pl022,wait-state = <0>;
+			pl022,duplex = <0>;
+		};
+	};
+	

drivers/spi/spi-pl022.c

···
 	return -ENODEV;
 }
 
+static int pl022_dma_autoprobe(struct pl022 *pl022)
+{
+	struct device *dev = &pl022->adev->dev;
+
+	/* automatically configure DMA channels from platform, normally using DT */
+	pl022->dma_rx_channel = dma_request_slave_channel(dev, "rx");
+	if (!pl022->dma_rx_channel)
+		goto err_no_rxchan;
+
+	pl022->dma_tx_channel = dma_request_slave_channel(dev, "tx");
+	if (!pl022->dma_tx_channel)
+		goto err_no_txchan;
+
+	pl022->dummypage = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!pl022->dummypage)
+		goto err_no_dummypage;
+
+	return 0;
+
+err_no_dummypage:
+	dma_release_channel(pl022->dma_tx_channel);
+	pl022->dma_tx_channel = NULL;
+err_no_txchan:
+	dma_release_channel(pl022->dma_rx_channel);
+	pl022->dma_rx_channel = NULL;
+err_no_rxchan:
+	return -ENODEV;
+}
+		
 static void terminate_dma(struct pl022 *pl022)
 {
 	struct dma_chan *rxchan = pl022->dma_rx_channel;
···
 static inline int configure_dma(struct pl022 *pl022)
 {
 	return -ENODEV;
+}
+
+static inline int pl022_dma_autoprobe(struct pl022 *pl022)
+{
+	return 0;
 }
 
 static inline int pl022_dma_probe(struct pl022 *pl022)
···
 		goto err_no_irq;
 	}
 
-	/* Get DMA channels */
-	if (platform_info->enable_dma) {
+	/* Get DMA channels, try autoconfiguration first */
+	status = pl022_dma_autoprobe(pl022);
+
+	/* If that failed, use channels from platform_info */
+	if (status == 0)
+		platform_info->enable_dma = 1;
+	else if (platform_info->enable_dma) {
 		status = pl022_dma_probe(pl022);
 		if (status != 0)
 			platform_info->enable_dma = 0;