[Letux-kernel] [Internal RFC 02/16] arm: dts: omap3pandora: Don't use DMA channels for unused SPI masters

[H. Nikolaus Schaller]

From: Grond <grond66 at riseup.net>

On the pandora, only mcspi1 (spi0) is actually used. Because the device
tree defaults in arch/arm/boot/dts/omap3.dtsi leave all of the mcspi
interfaces enabled, the DMA channels which the device tree assigns to them
cannot be used for anything else. This is a problem because OMAP3's sDMA
controller can only have 32 DMA channels configured at any one time.

So when we try to use (for example) the McBSP subsystem (which is required
for sound) it doesn't work because we've already exhausted our available
DMA channels.

Fix this by disabling mcspi[2-4] on the pandora device tree.

Signed-off-by: Grond <grond66 at riseup.net>
Signed-off-by: H. Nikolaus Schaller <hns at goldelico.com>
---
 arch/arm/boot/dts/omap3-pandora-common.dtsi | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/arm/boot/dts/omap3-pandora-common.dtsi b/arch/arm/boot/dts/omap3-pandora-common.dtsi
index 559853764487f..898f894c63059 100644
--- a/arch/arm/boot/dts/omap3-pandora-common.dtsi
+++ b/arch/arm/boot/dts/omap3-pandora-common.dtsi
@@ -685,6 +685,23 @@ lcd_in: endpoint {
 
 };
 
+/*
+ * Only mcspi1 is used on the pandora, the others do not surface on the board
+ * due to pinmux configuration. disable the unused ones so that they do not
+ * consume DMA channels
+ */
+&mcspi2 {
+	status = "disabled";
+};
+
+&mcspi3 {
+	status = "disabled";
+};
+
+&mcspi4 {
+	status = "disabled";
+};
+
 /* n/a - used as GPIOs */
 &mcbsp1 {
 };
-- 
2.33.0