Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2;
From:   Richard Laing <richard.laing@alliedtelesis.co.nz>
To:     gregkh@linuxfoundation.org, jirislaby@kernel.org,
        robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        conor+dt@kernel.org, ilpo.jarvinen@linux.intel.com,
        andriy.shevchenko@linux.intel.com
Cc:     linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
        devicetree@vger.kernel.org,
        Richard Laing <richard.laing@alliedtelesis.co.nz>
Subject: [PATCH] dt-bindings: serial: snps-dw-apb-uart: Add property to drain TX FIFO
Date:   Mon, 16 Oct 2023 14:32:07 +1300
Message-ID: <20231016013207.2249946-3-richard.laing@alliedtelesis.co.nz>
In-Reply-To: <20231016013207.2249946-1-richard.laing@alliedtelesis.co.nz>
References: <20231016013207.2249946-1-richard.laing@alliedtelesis.co.nz>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

An issue has been observed on the Broadcom BCM56160 serial port which
appears closely related to a similar issue on the Marvell Armada 38x
serial port.

Add a new property to force the TX FIFO to be drained before
changing the UART_LCR.

Signed-off-by: Richard Laing <richard.laing@alliedtelesis.co.nz>
---
 .../devicetree/bindings/serial/snps-dw-apb-uart.yaml        | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.ya=
ml b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
index 17c553123f96..4266ef96832c 100644
--- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
+++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
@@ -114,6 +114,12 @@ properties:
       register. Define this if your serial port does not use this pin.
     type: boolean
=20
+  drain-before-lcr-change:
+    description: Force TX buffer flush before LCR change. Make sure all
+    characters in the buffer are sent before reconfiguring. Define this =
if
+    the UART drops its FIFO when reconfiguring.
+    type: boolean
+
 required:
   - compatible
   - reg
--=20
2.42.0