1 files changed, 50 insertions, 0 deletions
diff --git a/target/linux/bcm27xx/patches-5.4/950-0034-amba_pl011-Add-cts-event-workaround-DT-property.patch b/target/linux/bcm27xx/patches-5.4/950-0034-amba_pl011-Add-cts-event-workaround-DT-property.patch
new file mode 100644
index 0000000000..efa24ac9e9
--- /dev/null
+++ b/target/linux/bcm27xx/patches-5.4/950-0034-amba_pl011-Add-cts-event-workaround-DT-property.patch
@@ -0,0 +1,50 @@
+From 2cb280484c8dde281972690cd67299005a796485 Mon Sep 17 00:00:00 2001
+From: Phil Elwell <phil@raspberrypi.org>
+Date: Fri, 29 Sep 2017 10:32:19 +0100
+Subject: [PATCH] amba_pl011: Add cts-event-workaround DT property
+
+The BCM2835 PL011 implementation seems to have a bug that can lead to a
+transmission lockup if CTS changes frequently. A workaround was added to
+the driver with a vendor-specific flag to enable it, but this flag is
+currently not set for ARM implementations.
+
+Add a "cts-event-workaround" property to Pi DTBs and use the presence
+of that property to force the flag to be enabled in the driver.
+
+See: https://github.com/raspberrypi/linux/issues/1280
+
+Signed-off-by: Phil Elwell <phil@raspberrypi.org>
+---
+ Documentation/devicetree/bindings/serial/pl011.yaml | 6 ++++++
+ drivers/tty/serial/amba-pl011.c                     | 5 +++++
+ 2 files changed, 11 insertions(+)
+
+--- a/Documentation/devicetree/bindings/serial/pl011.yaml
++++ b/Documentation/devicetree/bindings/serial/pl011.yaml
+@@ -100,6 +100,12 @@ properties:
+       - $ref: /schemas/types.yaml#/definitions/uint32
+       - default: 3000
+ 
++  cts-event-workaround:
++    description:
++      Enables the (otherwise vendor-specific) workaround for the
++      CTS-induced TX lockup.
++    type: boolean
++
+ required:
+   - compatible
+   - reg
+--- a/drivers/tty/serial/amba-pl011.c
++++ b/drivers/tty/serial/amba-pl011.c
+@@ -2659,6 +2659,11 @@ static int pl011_probe(struct amba_devic
+ 	if (IS_ERR(uap->clk))
+ 		return PTR_ERR(uap->clk);
+ 
++	if (of_property_read_bool(dev->dev.of_node, "cts-event-workaround")) {
++	    vendor->cts_event_workaround = true;
++	    dev_info(&dev->dev, "cts_event_workaround enabled\n");
++	}
++
+ 	uap->reg_offset = vendor->reg_offset;
+ 	uap->vendor = vendor;
+ 	uap->fifosize = vendor->get_fifosize(dev);