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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Ryan Case <ryandcase@chromium.org>,
        Evan Green <evgreen@chromium.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 54/97] tty: serial: qcom_geni_serial: Fix UART hang
Date:   Thu, 27 Feb 2020 14:37:02 +0100
Message-Id: <20200227132223.401435581@linuxfoundation.org>
In-Reply-To: <20200227132214.553656188@linuxfoundation.org>
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From: Ryan Case <ryandcase@chromium.org>

[ Upstream commit 663abb1a7a7ff8fea9ab0145463de7fcff823755 ]

If a serial console write occured while a UART transmit command was
waiting for a done signal then no further data would be sent until
something new kicked the system into gear. If there is already data
waiting in the circular buffer we must re-enable the tx watermark so we
receive the expected interrupts.

Signed-off-by: Ryan Case <ryandcase@chromium.org>
Reviewed-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/qcom_geni_serial.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index b3f7d1a1e97f8..2003dfcace5d8 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -438,6 +438,7 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s,
 	bool locked = true;
 	unsigned long flags;
 	u32 geni_status;
+	u32 irq_en;
 
 	WARN_ON(co->index < 0 || co->index >= GENI_UART_CONS_PORTS);
 
@@ -472,6 +473,13 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s,
 		 * has been sent, in which case we need to look for done first.
 		 */
 		qcom_geni_serial_poll_tx_done(uport);
+
+		if (uart_circ_chars_pending(&uport->state->xmit)) {
+			irq_en = readl_relaxed(uport->membase +
+					SE_GENI_M_IRQ_EN);
+			writel_relaxed(irq_en | M_TX_FIFO_WATERMARK_EN,
+					uport->membase + SE_GENI_M_IRQ_EN);
+		}
 	}
 
 	__qcom_geni_serial_console_write(uport, s, count);
-- 
2.20.1