target/linux/brcm2708/patches-4.19/950-0036-amba_pl011-Add-cts-event-workaround-DT-property.patch

   1 From 17a4507175ca6018ea40e91c9d753bc39f043d99 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.txt | 3 +++
  19  drivers/tty/serial/amba-pl011.c                    | 5 +++++
  20  2 files changed, 8 insertions(+)
  21
  22 --- a/Documentation/devicetree/bindings/serial/pl011.txt
  23 +++ b/Documentation/devicetree/bindings/serial/pl011.txt
  24 @@ -35,6 +35,9 @@ Optional properties:
  25  - poll-timeout-ms:
  26            Poll timeout when auto-poll is set, default
  27            3000ms.
  28 +- cts-event-workaround:
  29 +          Enables the (otherwise vendor-specific) workaround for the
  30 +          CTS-induced TX lockup.
  31
  32  See also bindings/arm/primecell.txt
  33
  34 --- a/drivers/tty/serial/amba-pl011.c
  35 +++ b/drivers/tty/serial/amba-pl011.c
  36 @@ -2659,6 +2659,11 @@ static int pl011_probe(struct amba_devic
  37         if (IS_ERR(uap->clk))
  38                 return PTR_ERR(uap->clk);
  39
  40 +       if (of_property_read_bool(dev->dev.of_node, "cts-event-workaround")) {
  41 +           vendor->cts_event_workaround = true;
  42 +           dev_info(&dev->dev, "cts_event_workaround enabled\n");
  43 +       }
  44 +
  45         uap->reg_offset = vendor->reg_offset;
  46         uap->vendor = vendor;
  47         uap->fifosize = vendor->get_fifosize(dev);