linux-kernel - [PATCH 1/3] serial: xilinx_uartps: Let get

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Date:   Mon, 25 Nov 2019 18:32:39 +0530
From:   shubhrajyoti.datta@...il.com
To:     linux-kernel@...r.kernel.org
Cc:     michal.simek@...inx.com, gregkh@...uxfoundation.org, arnd@...db.de,
        Maarten Brock <m.brock@...mierlo.com>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
Subject: [PATCH 1/3] serial: xilinx_uartps: Let get_mctrl return status

From: Maarten Brock <m.brock@...mierlo.com>

Some of the applications like microcom do not work if
modem is disabled. To fix them we always return
TIOCM_CTS | TIOCM_DSR | TIOCM_CAR instead of 0 when
using cts_override. Make get_mctrl return actual status
when not using cts_override.

Signed-off-by: Maarten Brock <m.brock@...mierlo.com>
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
---
 drivers/tty/serial/xilinx_uartps.c | 38 +++++++++++++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 4e55bc3..9e12589 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -158,6 +158,26 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
 #define CDNS_UART_MODEMCR_DTR	0x00000001 /* Data Terminal Ready */
 
 /*
+ * Modem Status register:
+ * The read/write Modem Status register reports the interface with the modem
+ * or data set, or a peripheral device emulating a modem.
+ */
+#define CDNS_UART_MODEMSR_DCD	BIT(7) /* Data Carrier Detect */
+#define CDNS_UART_MODEMSR_RI	BIT(6) /* Ting Indicator */
+#define CDNS_UART_MODEMSR_DSR	BIT(5) /* Data Set Ready */
+#define CDNS_UART_MODEMSR_CTS	BIT(4) /* Clear To Send */
+
+/*
+ * Modem Status register:
+ * The read/write Modem Status register reports the interface with the modem
+ * or data set, or a peripheral device emulating a modem.
+ */
+#define CDNS_UART_MODEMSR_DCD	BIT(7) /* Data Carrier Detect */
+#define CDNS_UART_MODEMSR_RI	BIT(6) /* Ting Indicator */
+#define CDNS_UART_MODEMSR_DSR	BIT(5) /* Data Set Ready */
+#define CDNS_UART_MODEMSR_CTS	BIT(4) /* Clear To Send */
+
+/*
  * Channel Status Register:
  * The channel status register (CSR) is provided to enable the control logic
  * to monitor the status of bits in the channel interrupt status register,
@@ -1007,12 +1027,24 @@ static void cdns_uart_config_port(struct uart_port *port, int flags)
  */
 static unsigned int cdns_uart_get_mctrl(struct uart_port *port)
 {
+	u32 val;
+	unsigned int mctrl = 0;
 	struct cdns_uart *cdns_uart_data = port->private_data;
 
 	if (cdns_uart_data->cts_override)
-		return 0;
-
-	return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
+		return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
+
+	val = readl(port->membase + CDNS_UART_MODEMSR);
+	if (val & CDNS_UART_MODEMSR_CTS)
+		mctrl |= TIOCM_CTS;
+	if (val & CDNS_UART_MODEMSR_DSR)
+		mctrl |= TIOCM_DSR;
+	if (val & CDNS_UART_MODEMSR_RI)
+		mctrl |= TIOCM_RNG;
+	if (val & CDNS_UART_MODEMSR_DCD)
+		mctrl |= TIOCM_CAR;
+
+	return mctrl;
 }
 
 static void cdns_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
-- 
2.1.1