dmaengine: ste_dma40: Fetch disabled channels from DT

Some platforms have channels which are not available for normal use.
This information is currently passed though platform data in internal
BSP kernels. Once those platforms land, they'll need to configure them
appropriately, so we may as well add the infrastructure.

Cc: Dan Williams <[e-mail]>
Cc: Per Forlin <[e-mail]>
Cc: Rabin Vincent <[e-mail]>
Acked-by: Vinod Koul <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

Documentation/devicetree/bindings/dma/ste-dma40.txt

···
 Optional properties:
 - dma-channels: Number of channels supported by hardware - if not present
 		the driver will attempt to obtain the information from H/W
+- disabled-channels: Channels which can not be used
 
 Example:
 
···
 
 		#dma-cells = <2>;
 		memcpy-channels  = <56 57 58 59 60>;
+		disabled-channels  = <12>;
 		dma-channels = <8>;
 	};
 

drivers/dma/ste_dma40.c

···
 			       struct device_node *np)
 {
 	struct stedma40_platform_data *pdata;
-	int num_phy = 0, num_memcpy = 0;
+	int num_phy = 0, num_memcpy = 0, num_disabled = 0;
 	const const __be32 *list;
 
 	pdata = devm_kzalloc(&pdev->dev,
···
 	of_property_read_u32_array(np, "memcpy-channels",
 				   dma40_memcpy_channels,
 				   num_memcpy);
+
+	list = of_get_property(np, "disabled-channels", &num_disabled);
+	num_disabled /= sizeof(*list);
+
+	if (num_disabled > STEDMA40_MAX_PHYS || num_disabled < 0) {
+		d40_err(&pdev->dev,
+			"Invalid number of disabled channels specified (%d)\n",
+			num_disabled);
+		return -EINVAL;
+	}
+
+	of_property_read_u32_array(np, "disabled-channels",
+				   pdata->disabled_channels,
+				   num_disabled);
+	pdata->disabled_channels[num_disabled] = -1;
 
 	pdev->dev.platform_data = pdata;