[PATCH 1/2] serial/aspeed-vuart: Only disable host tx discard when serial port is in use

[Norman James]

I tried this with various cases of console usage.  Starting console in
beginning, in the middle, never, etc.  Seems to work.  Please get merged
ASAP.  Thanks!


Regards,
Norman James
IBM - POWER Systems Architect
Phone: 1-512-286-6807 (T/L: 363-6807)
Internet: njames at us.ibm.com




From:	Jeremy Kerr <jk at ozlabs.org>
To:	openbmc at lists.ozlabs.org
Date:	02/11/2016 03:03 AM
Subject:	[PATCH 1/2] serial/aspeed-vuart: Only disable host tx discard
            when serial port is in use
Sent by:	"openbmc" <openbmc-bounces+njames=us.ibm.com at lists.ozlabs.org>



OpenPOWER firmware doesn't like it when the host-side of the VUART's
FIFO is not drained. This change shifts only disables host TX discard
mode when the port has been opened.

Signed-off-by: Jeremy Kerr <jk at ozlabs.org>
---
 drivers/tty/serial/aspeed-vuart.c | 40 ++++++++++++++++++++++++++++++++++
+----
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/aspeed-vuart.c
b/drivers/tty/serial/aspeed-vuart.c
index f34884a..73bb0e7 100644
--- a/drivers/tty/serial/aspeed-vuart.c
+++ b/drivers/tty/serial/aspeed-vuart.c
@@ -144,16 +144,45 @@ static ssize_t ast_vuart_set_sirq(struct device *dev,
 static DEVICE_ATTR(sirq, S_IWUSR | S_IRUGO,
 		 		 ast_vuart_show_sirq, ast_vuart_set_sirq);

-static void ast_vuart_setup(struct ast_vuart *vuart)
+static void ast_vuart_set_host_tx_discard(struct ast_vuart *vuart, bool
discard)
 {
 		 u8 reg;

-		 /* disable TX discard mode */
 		 reg = readb(vuart->regs + AST_VUART_GCRA);
-		 reg |= AST_VUART_GCRA_HOST_TX_DISCARD;
+
+		 /* if the HOST_TX_DISCARD bit is set, discard is *disabled* */
+		 reg &= ~AST_VUART_GCRA_HOST_TX_DISCARD;
+		 if (!discard)
+		 		 reg |= AST_VUART_GCRA_HOST_TX_DISCARD;
+
 		 writeb(reg, vuart->regs + AST_VUART_GCRA);
 }

+static int ast_vuart_startup(struct uart_port *uart_port)
+{
+		 struct uart_8250_port *uart_8250_port = up_to_u8250p
(uart_port);
+		 struct ast_vuart *vuart = uart_8250_port->port.private_data;
+		 int rc;
+
+		 rc = serial8250_do_startup(uart_port);
+		 if (rc)
+		 		 return rc;
+
+		 ast_vuart_set_host_tx_discard(vuart, false);
+
+		 return 0;
+}
+
+static void ast_vuart_shutdown(struct uart_port *uart_port)
+{
+		 struct uart_8250_port *uart_8250_port = up_to_u8250p
(uart_port);
+		 struct ast_vuart *vuart = uart_8250_port->port.private_data;
+
+		 ast_vuart_set_host_tx_discard(vuart, true);
+
+		 serial8250_do_shutdown(uart_port);
+}
+

 /**
  * The device tree parsing code here is heavily based on that of the
of_serial
@@ -190,9 +219,12 @@ static int ast_vuart_probe(struct platform_device
*pdev)
 		 }

 		 memset(&port, 0, sizeof(port));
+		 port.port.private_data = vuart;
 		 port.port.membase = vuart->regs;
 		 port.port.mapbase = resource.start;
 		 port.port.mapsize = resource_size(&resource);
+		 port.port.startup = ast_vuart_startup;
+		 port.port.shutdown = ast_vuart_shutdown;

 		 if (of_property_read_u32(np, "clock-frequency", &clk)) {
 		 		 vuart->clk = devm_clk_get(&pdev->dev, NULL);
@@ -272,8 +304,8 @@ static int ast_vuart_probe(struct platform_device
*pdev)


 		 vuart->line = rc;
+		 ast_vuart_set_host_tx_discard(vuart, true);
 		 platform_set_drvdata(pdev, vuart);
-		 ast_vuart_setup(vuart);

 		 /* extra sysfs control */
 		 rc = device_create_file(&pdev->dev, &dev_attr_lpc_address);
--
2.5.0

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