From b60ea6c0170c149888dca480c0f6f25b2bc5b8f3 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.txt | 3 +++ arch/arm/boot/dts/bcm270x.dtsi | 5 +++++ drivers/tty/serial/amba-pl011.c | 5 +++++ 3 files changed, 13 insertions(+) diff --git a/Documentation/devicetree/bindings/serial/pl011.txt b/Documentation/devicetree/bindings/serial/pl011.txt index 77863aefe9ef..8d65b0ec2828 100644 --- a/Documentation/devicetree/bindings/serial/pl011.txt +++ b/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 diff --git a/arch/arm/boot/dts/bcm270x.dtsi b/arch/arm/boot/dts/bcm270x.dtsi index caa663935186..6af5a3651377 100644 --- a/arch/arm/boot/dts/bcm270x.dtsi +++ b/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>; diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index a17489a1174e..460c7d3e2962 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/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); -- 2.30.2