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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,
        Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Stephen Boyd <swboyd@chromium.org>
Subject: [PATCH 4.14 48/69] tty: serial: msm_serial: Fix XON/XOFF
Date:   Fri,  7 Jun 2019 17:39:29 +0200
Message-Id: <20190607153854.275715769@linuxfoundation.org>
In-Reply-To: <20190607153848.271562617@linuxfoundation.org>
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From: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>

commit 61c0e37950b88bad590056286c1d766b1f167f4e upstream.

When the tty layer requests the uart to throttle, the current code
executing in msm_serial will trigger "Bad mode in Error Handler" and
generate an invalid stack frame in pstore before rebooting (that is if
pstore is indeed configured: otherwise the user shall just notice a
reboot with no further information dumped to the console).

This patch replaces the PIO byte accessor with the word accessor
already used in PIO mode.

Fixes: 68252424a7c7 ("tty: serial: msm: Support big-endian CPUs")
Cc: stable@vger.kernel.org
Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/tty/serial/msm_serial.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -868,6 +868,7 @@ static void msm_handle_tx(struct uart_po
 	struct circ_buf *xmit = &msm_port->uart.state->xmit;
 	struct msm_dma *dma = &msm_port->tx_dma;
 	unsigned int pio_count, dma_count, dma_min;
+	char buf[4] = { 0 };
 	void __iomem *tf;
 	int err = 0;
 
@@ -877,10 +878,12 @@ static void msm_handle_tx(struct uart_po
 		else
 			tf = port->membase + UART_TF;
 
+		buf[0] = port->x_char;
+
 		if (msm_port->is_uartdm)
 			msm_reset_dm_count(port, 1);
 
-		iowrite8_rep(tf, &port->x_char, 1);
+		iowrite32_rep(tf, buf, 1);
 		port->icount.tx++;
 		port->x_char = 0;
 		return;