i.MX: Support serial RS-232 break properly

Linux does not detect a break from this IMX serial driver as a magic
sysrq.  Nor does it note a break in the port error counts.

The former is because the Linux driver uses the BRCD bit in the USR2
register to trigger the RS-232 break handler in the kernel, which is
where sysrq hooks in.  The emulated UART was not setting this status
bit.

The latter is because the Linux driver expects, in addition to the BRK
bit, that the ERR bit is set when a break is read in the FIFO.  A break
should also count as a frame error, so add that bit too.

Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Trent Piepho <tpiepho@impinj.com>
Message-id: 20180320013657.25038-1-tpiepho@impinj.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/hw/char/imx_serial.c b/hw/char/imx_serial.c
index 1e5540472b91e4dd2a454962a7a8c3457dfb3fe8..0747db9f2b91744a13c58a2dd92ef04265199617 100644 (file)
--- a/hw/char/imx_serial.c
+++ b/hw/char/imx_serial.c
@@ -308,6 +308,9 @@ static void imx_put_data(void *opaque, uint32_t value)
     s->usr2 |= USR2_RDR;
     s->uts1 &= ~UTS1_RXEMPTY;
     s->readbuff = value;
+    if (value & URXD_BRK) {
+        s->usr2 |= USR2_BRCD;
+    }
     imx_update(s);
 }
 
@@ -319,7 +322,7 @@ static void imx_receive(void *opaque, const uint8_t *buf, int size)
 static void imx_event(void *opaque, int event)
 {
     if (event == CHR_EVENT_BREAK) {
-        imx_put_data(opaque, URXD_BRK);
+        imx_put_data(opaque, URXD_BRK | URXD_FRMERR | URXD_ERR);
     }
 }
 

diff --git a/include/hw/char/imx_serial.h b/include/hw/char/imx_serial.h
index 5b99cee7cfa093483b765f6cfd7ada214865cc06..ee80da12e602190bcc1428b67447df828e678b34 100644 (file)
--- a/include/hw/char/imx_serial.h
+++ b/include/hw/char/imx_serial.h
@@ -26,6 +26,7 @@
 
 #define URXD_CHARRDY    (1<<15)   /* character read is valid */
 #define URXD_ERR        (1<<14)   /* Character has error */
+#define URXD_FRMERR     (1<<12)   /* Character has frame error */
 #define URXD_BRK        (1<<11)   /* Break received */
 
 #define USR1_PARTYER    (1<<15)   /* Parity Error */