linux-kernel - [PATCH] serial: 8250: Do XR17V35X specific wakeup in serial8250_do

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Message-Id: <1434726737-2585-1-git-send-email-joro@8bytes.org>
Date:	Fri, 19 Jun 2015 17:12:17 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.cz>, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org, Joerg Roedel <jroedel@...e.de>,
	Peter Hurley <peter@...leysoftware.com>,
	Michael Welling <mwelling@...e.org>,
	Joe Schultz <jschultz@...-inc.com>
Subject: [PATCH] serial: 8250: Do XR17V35X specific wakeup in serial8250_do_startup

From: Joerg Roedel <jroedel@...e.de>

While debugging why my 8-port XR17V35X card does not work
with the in-kernel serial driver, I found that some chip
specific wakeup code is necessary to get it working.

Specificly the EFR_ECB bit needs to be set in the
chip-specific UART_XR_EFR register, so that writing to a
couple of other configuration bits is enabled.

Cc: Peter Hurley <peter@...leysoftware.com>
Cc: Michael Welling <mwelling@...e.org>
Cc: Joe Schultz <jschultz@...-inc.com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/tty/serial/8250/8250_core.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 4506e40..de34db3 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -2176,6 +2176,18 @@ int serial8250_do_startup(struct uart_port *port)
 	 */
 	enable_rsa(up);
 #endif
+
+	/*
+	 * Do this right before clearing the FIFOs to prevent
+	 * interrupt storm.
+	 */
+	if (port->type == PORT_XR17V35X) {
+		/* Wake up and initialize UART */
+		serial_port_out(port, UART_XR_EFR, UART_EFR_ECB);
+		serial_port_out(port, UART_IER, 0);
+		serial_port_out(port, UART_LCR, 0);
+	}
+
 	/*
 	 * Clear the FIFO buffers and disable them.
 	 * (they will be reenabled in set_termios())
-- 
1.8.4.5

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