linux-kernel - [PATCH 20/20] serial: stm32: fix rx interrupt handling in startup

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Date:   Mon, 26 Jun 2017 12:49:17 +0000
From:   Bich HEMON <bich.hemon@...com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "Jiri Slaby" <jslaby@...e.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Bich HEMON <bich.hemon@...com>
Subject: [PATCH 20/20] serial: stm32: fix rx interrupt handling in startup

From: Bich Hemon <bich.hemon@...com>

When stm32 dma is used, Data register has to be read in order
to clear the RXNE interrupt in case we received data before
usart probe.

Signed-off-by: Bich Hemon <bich.hemon@...com>
---
 drivers/tty/serial/stm32-usart.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 06a92c8..b1f3aab 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -568,9 +568,18 @@ static int stm32_startup(struct uart_port *port)
 	struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
 	struct stm32_usart_config *cfg = &stm32_port->info->cfg;
 	const char *name = to_platform_device(port->dev)->name;
-	u32 val;
+	u32 val, sr, dr;
 	int ret;
 
+	sr = readl_relaxed(port->membase + ofs->isr);
+
+	if ((sr & USART_SR_RXNE) && (stm32_port->rx_ch))
+		ret = readl_relaxed_poll_timeout_atomic(port->membase +
+							ofs->rdr,
+							dr,
+							!(sr & USART_SR_RXNE),
+							10, 100000);
+
 	ret = request_threaded_irq(port->irq, stm32_interrupt,
 				   stm32_threaded_interrupt,
 				   IRQF_NO_SUSPEND, name, port);
-- 
1.9.1