virtio-serial: Rework shutdown sequence

The "io" word of term-io.fs opens two separate instances of the device
for stdin and stdout. The prom_init() function in Linux closes stdin at
some point, which internally calls quiesce and shuts the device down
through a quiesce hook.

When the "open-count" variable in virtio-serial.fs reaches 0, ie. when
closing the last instance, we call "close" two times, which is clearly
wrong. This never hits however because the stdout instance is never
closed which prevents "open-count" to reach 0.

It would make more sense to shutdown the device when closing the last
instance, for symmetry with the first open that initializes the device.
Change the shutdown sequence to do that rather than relying on a quiesce
hook.

Have quiesce to explicitly close stdout, which is supposedly the last
instance, and shutdown the device.

Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

board-qemu/slof/virtio-serial.fs

diff --git a/board-qemu/slof/virtio-serial.fs b/board-qemu/slof/virtio-serial.fs
index a99293f..e307231 100644
--- a/board-qemu/slof/virtio-serial.fs
+++ b/board-qemu/slof/virtio-serial.fs
@@ -19,13 +19,8 @@
 \ Quiescence the virtqueue of this device so that no more background
 \ transactions can be pending.
 : shutdown  ( -- )
-    initialized? IF
-        my-phandle node>path open-dev ?dup IF
-            virtiodev virtio-serial-shutdown
-            close-dev
-        THEN
-        FALSE to initialized?
-    THEN
+    virtiodev virtio-serial-shutdown
+    FALSE to initialized?
 ;
 
 : virtio-serial-term-emit
@@ -39,7 +34,6 @@
 : init  ( -- )
 virtiodev virtio-serial-init drop
     TRUE to initialized?
-    ['] shutdown add-quiesce-xt
 ;
 
 0 VALUE open-count
@@ -58,7 +52,7 @@
 : close
     open-count 0> IF
         open-count 1 - dup to open-count
-        0= IF close THEN
+        0= IF shutdown THEN
     THEN
     close
 ;

slof/fs/client.fs

diff --git a/slof/fs/client.fs b/slof/fs/client.fs
index db7a192..76231f9 100644
--- a/slof/fs/client.fs
+++ b/slof/fs/client.fs
@@ -203,6 +203,11 @@
 	    \ End of life of SLOF now, call platform quiesce as quiesce
 	    \ is an undocumented extension and not everybody supports it
 	    close-dev
+	    \ Some device, eg. virtio-serial, need all instances to be
+	    \ closed in order to be reset properly
+	    s" stdout" get-chosen IF
+		decode-int nip nip close-dev
+	    THEN
 	    quiesce
 	ELSE
 	    close-dev