linux-kernel - [PATCH 04/14] serial: tegra: protect IER against LCR.DLAB

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Message-ID: <1565609303-27000-5-git-send-email-kyarlagadda@nvidia.com>
Date:   Mon, 12 Aug 2019 16:58:13 +0530
From:   Krishna Yarlagadda <kyarlagadda@...dia.com>
To:     <gregkh@...uxfoundation.org>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <ldewangan@...dia.com>, <jslaby@...e.com>
CC:     <linux-serial@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Ahung Cheng <ahcheng@...dia.com>,
        Krishna Yarlagadda <kyarlagadda@...dia.com>
Subject: [PATCH 04/14] serial: tegra: protect IER against LCR.DLAB

From: Ahung Cheng <ahcheng@...dia.com>

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@...dia.com>
Signed-off-by: Krishna Yarlagadda <kyarlagadda@...dia.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 d908465..ae7225c 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -296,6 +296,7 @@ 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)
@@ -315,6 +316,7 @@ 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);
@@ -327,6 +329,7 @@ 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;
 
-- 
2.7.4