From: Ahung Cheng <ahcheng@nvidia.com>
Date: Mon, 12 Aug 2019 16:58:13 +0530
Subject: serial: tegra: protect IER against LCR.DLAB

Git-commit: 18a4c404d2b4de47da519955ddda0b153c03f12d
Patch-mainline: v5.4-rc1
References: jsc#SLE-9391,jsc#SLE-9388,jsc#SLE-10608

The IER and DLH registers occupy the same address space, selected by
the LCR.DLAB bit. Hence, add port lock to protect IER when LCR.DLAB bit
is set.

Signed-off-by: Ahung Cheng <ahcheng@nvidia.com>
Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/1565609303-27000-5-git-send-email-kyarlagadda@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 drivers/tty/serial/serial-tegra.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 83cc8dca58d4..82a8d5130cbc 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -294,6 +294,7 @@ static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
 	unsigned long rate;
 	unsigned int divisor;
 	unsigned long lcr;
+	unsigned long flags;
 	int ret;
 
 	if (tup->current_baud == baud)
@@ -313,6 +314,7 @@ static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
 		divisor = DIV_ROUND_CLOSEST(rate, baud * 16);
 	}
 
+	spin_lock_irqsave(&tup->uport.lock, flags);
 	lcr = tup->lcr_shadow;
 	lcr |= UART_LCR_DLAB;
 	tegra_uart_write(tup, lcr, UART_LCR);
@@ -325,6 +327,7 @@ static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
 
 	/* Dummy read to ensure the write is posted */
 	tegra_uart_read(tup, UART_SCR);
+	spin_unlock_irqrestore(&tup->uport.lock, flags);
 
 	tup->current_baud = baud;
 
-- 
2.16.4