From 2cb280484c8dde281972690cd67299005a796485 Mon Sep 17 00:00:00 2001 From: Phil Elwell 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 --- 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);