Patchwork hvc_vio: Improve registration of udbg backend

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Submitter Benjamin Herrenschmidt
Date July 24, 2012, 7:47 a.m.
Message ID <1343116058.3715.20.camel@pasglop>
Download mbox | patch
Permalink /patch/172800/
State Accepted, archived
Commit d1cfc0ce5d3196ccd88b9d868bb7cbcab61e0a31
Delegated to: Benjamin Herrenschmidt
Headers show

Comments

Benjamin Herrenschmidt - July 24, 2012, 7:47 a.m.
The pseries hvterm driver only registers a udbg backend (for xmon and
other low level debugging mechanisms) when hvc0 is recognized as the
firmware console at boot time, not if it's detected later on, for
example because the firmware is using a graphics card.

This can make debugging challenging especially under X11, and there's
really no good reason for that limitation, so let's hookup udbg
whenever hvc0 is detected instead.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

Patch

diff --git a/drivers/tty/hvc/hvc_vio.c b/drivers/tty/hvc/hvc_vio.c
index ee30779..070c0ee6 100644
--- a/drivers/tty/hvc/hvc_vio.c
+++ b/drivers/tty/hvc/hvc_vio.c
@@ -230,6 +230,69 @@  static const struct hv_ops hvterm_hvsi_ops = {
 	.tiocmset = hvterm_hvsi_tiocmset,
 };
 
+static void udbg_hvc_putc(char c)
+{
+	int count = -1;
+
+	if (!hvterm_privs[0])
+		return;
+
+	if (c == '\n')
+		udbg_hvc_putc('\r');
+
+	do {
+		switch(hvterm_privs[0]->proto) {
+		case HV_PROTOCOL_RAW:
+			count = hvterm_raw_put_chars(0, &c, 1);
+			break;
+		case HV_PROTOCOL_HVSI:
+			count = hvterm_hvsi_put_chars(0, &c, 1);
+			break;
+		}
+	} while(count == 0);
+}
+
+static int udbg_hvc_getc_poll(void)
+{
+	int rc = 0;
+	char c;
+
+	if (!hvterm_privs[0])
+		return -1;
+
+	switch(hvterm_privs[0]->proto) {
+	case HV_PROTOCOL_RAW:
+		rc = hvterm_raw_get_chars(0, &c, 1);
+		break;
+	case HV_PROTOCOL_HVSI:
+		rc = hvterm_hvsi_get_chars(0, &c, 1);
+		break;
+	}
+	if (!rc)
+		return -1;
+	return c;
+}
+
+static int udbg_hvc_getc(void)
+{
+	int ch;
+
+	if (!hvterm_privs[0])
+		return -1;
+
+	for (;;) {
+		ch = udbg_hvc_getc_poll();
+		if (ch == -1) {
+			/* This shouldn't be needed...but... */
+			volatile unsigned long delay;
+			for (delay=0; delay < 2000000; delay++)
+				;
+		} else {
+			return ch;
+		}
+	}
+}
+
 static int __devinit hvc_vio_probe(struct vio_dev *vdev,
 				   const struct vio_device_id *id)
 {
@@ -289,6 +352,13 @@  static int __devinit hvc_vio_probe(struct vio_dev *vdev,
 		return PTR_ERR(hp);
 	dev_set_drvdata(&vdev->dev, hp);
 
+	/* register udbg if it's not there already for console 0 */
+	if (hp->index == 0 && !udbg_putc) {
+		udbg_putc = udbg_hvc_putc;
+		udbg_getc = udbg_hvc_getc;
+		udbg_getc_poll = udbg_hvc_getc_poll;
+	}
+
 	return 0;
 }
 
@@ -331,59 +401,6 @@  static void __exit hvc_vio_exit(void)
 }
 module_exit(hvc_vio_exit);
 
-static void udbg_hvc_putc(char c)
-{
-	int count = -1;
-
-	if (c == '\n')
-		udbg_hvc_putc('\r');
-
-	do {
-		switch(hvterm_priv0.proto) {
-		case HV_PROTOCOL_RAW:
-			count = hvterm_raw_put_chars(0, &c, 1);
-			break;
-		case HV_PROTOCOL_HVSI:
-			count = hvterm_hvsi_put_chars(0, &c, 1);
-			break;
-		}
-	} while(count == 0);
-}
-
-static int udbg_hvc_getc_poll(void)
-{
-	int rc = 0;
-	char c;
-
-	switch(hvterm_priv0.proto) {
-	case HV_PROTOCOL_RAW:
-		rc = hvterm_raw_get_chars(0, &c, 1);
-		break;
-	case HV_PROTOCOL_HVSI:
-		rc = hvterm_hvsi_get_chars(0, &c, 1);
-		break;
-	}
-	if (!rc)
-		return -1;
-	return c;
-}
-
-static int udbg_hvc_getc(void)
-{
-	int ch;
-	for (;;) {
-		ch = udbg_hvc_getc_poll();
-		if (ch == -1) {
-			/* This shouldn't be needed...but... */
-			volatile unsigned long delay;
-			for (delay=0; delay < 2000000; delay++)
-				;
-		} else {
-			return ch;
-		}
-	}
-}
-
 void __init hvc_vio_init_early(void)
 {
 	struct device_node *stdout_node;