rpi_1468_b60ea6c0170c149888dca480c0f6f25b2bc5b8f3

commit b60ea6c
Author: Phil Elwell <phil@raspberrypi.org>
Date:   Fri Sep 29 10:32:19 2017 +0100

    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: raspberrypi/linux#1280
    
    Signed-off-by: Phil Elwell <phil@raspberrypi.org>


Gbp-Pq: Topic rpi
Gbp-Pq: Name rpi_1468_b60ea6c0170c149888dca480c0f6f25b2bc5b8f3.patch

Documentation/devicetree/bindings/serial/pl011.txt

@@ -35,6 +35,9 @@ Optional properties:
 - poll-timeout-ms:
  Poll timeout when auto-poll is set, default
  3000ms.
+- cts-event-workaround:
+ Enables the (otherwise vendor-specific) workaround for the
+ CTS-induced TX lockup.
 
 See also bindings/arm/primecell.txt
 

arch/arm/boot/dts/bcm270x.dtsi

@@ -26,6 +26,11 @@
  interrupts = <2 17>, <2 18>;
  };
 
+ serial@7e201000 { /* uart0 */
+ /* Enable CTS bug workaround */
+ cts-event-workaround;
+ };
+
  sdhost: sdhost@7e202000 {
  compatible = "brcm,bcm2835-sdhost";
  reg = <0x7e202000 0x100>;

drivers/tty/serial/amba-pl011.c

@@ -2578,6 +2578,11 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
  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);