[Xen-changelog] [xen master] pl011: preserve RTS and DTR signal on UART init

[patchbot@xxxxxxx]

commit 4b272d61e8ac507ec98d075d41b56eb9ff83b596
Author:     Andre Przywara <andre.przywara@xxxxxxxxxx>
AuthorDate: Tue Sep 3 16:00:52 2013 +0200
Commit:     Ian Campbell <ian.campbell@xxxxxxxxxx>
CommitDate: Tue Sep 3 16:33:15 2013 +0100

    pl011: preserve RTS and DTR signal on UART init
    
    Although we do not support hardware flow control in the Xen driver
    for the PL011 UART, the other end may be configured to use it.
    In this case it waits in vain for the RTS signal to be asserted by
    the host and will never transmit any characters.
    So we leave RTS and DTR as they had been setup before.
    This fixes the UART input on Calxeda Midway, which uses hardware
    flow control for the serial-over-LAN functionality.
    
    Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
    Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 xen/drivers/char/pl011.c         |    7 +++++--
 xen/include/asm-arm/pl011-uart.h |    4 ++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/char/pl011.c b/xen/drivers/char/pl011.c
index 3ec6e10..3386e2b 100644
--- a/xen/drivers/char/pl011.c
+++ b/xen/drivers/char/pl011.c
@@ -85,6 +85,7 @@ static void __init pl011_init_preirq(struct serial_port *port)
 {
     struct pl011 *uart = port->uart;
     unsigned int divisor;
+    unsigned int cr;
 
     /* No interrupts, please. */
     pl011_write(uart, IMSC, 0);
@@ -120,8 +121,10 @@ static void __init pl011_init_preirq(struct serial_port 
*port)
     pl011_write(uart, IMSC, 0);
     pl011_write(uart, ICR, ALLI);
 
-    /* Enable the UART for RX and TX; no flow ctrl */
-    pl011_write(uart, CR, RXE | TXE | UARTEN);
+    /* Enable the UART for RX and TX; keep RTS and DTR */
+    cr = pl011_read(uart, CR);
+    cr &= RTS | DTR;
+    pl011_write(uart, CR, cr | RXE | TXE | UARTEN);
 }
 
 static void __init pl011_init_postirq(struct serial_port *port)
diff --git a/xen/include/asm-arm/pl011-uart.h b/xen/include/asm-arm/pl011-uart.h
index 3332c51..123f477 100644
--- a/xen/include/asm-arm/pl011-uart.h
+++ b/xen/include/asm-arm/pl011-uart.h
@@ -38,6 +38,10 @@
 #define DMACR  (0x48)
 
 /* CR bits */
+#define CTSEN  (1<<15) /* automatic CTS hardware flow control */
+#define RTSEN  (1<<14) /* automatic RTS hardware flow control */
+#define RTS    (1<<11) /* RTS signal */
+#define DTR    (1<<10) /* DTR signal */
 #define RXE    (1<<9) /* Receive enable */
 #define TXE    (1<<8) /* Transmit enable */
 #define UARTEN (1<<0) /* UART enable */
--
generated by git-patchbot for /home/xen/git/xen.git#master

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