target/linux/bcm27xx/patches-5.4/950-0034-amba_pl011-Add-cts-event-workaround-DT-property.patch

   1 From 2cb280484c8dde281972690cd67299005a796485 Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.org>
   3 Date: Fri, 29 Sep 2017 10:32:19 +0100
   4 Subject: [PATCH] amba_pl011: Add cts-event-workaround DT property
   5
   6 The BCM2835 PL011 implementation seems to have a bug that can lead to a
   7 transmission lockup if CTS changes frequently. A workaround was added to
   8 the driver with a vendor-specific flag to enable it, but this flag is
   9 currently not set for ARM implementations.
  10
  11 Add a "cts-event-workaround" property to Pi DTBs and use the presence
  12 of that property to force the flag to be enabled in the driver.
  13
  14 See: https://github.com/raspberrypi/linux/issues/1280
  15
  16 Signed-off-by: Phil Elwell <phil@raspberrypi.org>
  17 ---
  18  Documentation/devicetree/bindings/serial/pl011.yaml | 6 ++++++
  19  drivers/tty/serial/amba-pl011.c                     | 5 +++++
  20  2 files changed, 11 insertions(+)
  21
  22 --- a/Documentation/devicetree/bindings/serial/pl011.yaml
  23 +++ b/Documentation/devicetree/bindings/serial/pl011.yaml
  24 @@ -100,6 +100,12 @@ properties:
  25        - $ref: /schemas/types.yaml#/definitions/uint32
  26        - default: 3000
  27
  28 +  cts-event-workaround:
  29 +    description:
  30 +      Enables the (otherwise vendor-specific) workaround for the
  31 +      CTS-induced TX lockup.
  32 +    type: boolean
  33 +
  34  required:
  35    - compatible
  36    - reg
  37 --- a/drivers/tty/serial/amba-pl011.c
  38 +++ b/drivers/tty/serial/amba-pl011.c
  39 @@ -2659,6 +2659,11 @@ static int pl011_probe(struct amba_devic
  40         if (IS_ERR(uap->clk))
  41                 return PTR_ERR(uap->clk);
  42
  43 +       if (of_property_read_bool(dev->dev.of_node, "cts-event-workaround")) {
  44 +           vendor->cts_event_workaround = true;
  45 +           dev_info(&dev->dev, "cts_event_workaround enabled\n");
  46 +       }
  47 +
  48         uap->reg_offset = vendor->reg_offset;
  49         uap->vendor = vendor;
  50         uap->fifosize = vendor->get_fifosize(dev);