svn commit: r327815 - head/sys/powerpc/powernv

[Wojciech Macek]

Author: wma
Date: Thu Jan 11 09:42:24 2018
New Revision: 327815
URL: https://svnweb.freebsd.org/changeset/base/327815

Log:
  PowerNV: add buffer for OPAL console
  
  Avoid the lock in vtophys() by providing a static direct-mapped
  spinlock- protected output buffer to use when the console driver
  cannot acquire locks for some reason. This allows the idle thread
  to use printf() (e.g. the SMP startup messages) without crashing
  the kernel.
  
  Created by:            Nathan Whitehorn <nwhitehorn at freebsd.org>
  Submitted by:          Wojciech Macek <wma at freebsd.org>
  Sponsored by:          FreeBSD Foundation

Modified:
  head/sys/powerpc/powernv/opal_console.c

Modified: head/sys/powerpc/powernv/opal_console.c
==============================================================================
--- head/sys/powerpc/powernv/opal_console.c	Thu Jan 11 09:39:38 2018	(r327814)
+++ head/sys/powerpc/powernv/opal_console.c	Thu Jan 11 09:42:24 2018	(r327815)
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/types.h>
 #include <sys/conf.h>
 #include <sys/cons.h>
+#include <sys/proc.h>
 #include <sys/tty.h>
 
 #include <vm/vm.h>
@@ -72,6 +73,7 @@ struct uart_opal_softc {
 };
 
 static struct uart_opal_softc	*console_sc = NULL;
+
 #if defined(KDB)
 static int			alt_break_state;
 #endif
@@ -127,6 +129,48 @@ static struct ttydevsw uart_opal_tty_class = {
 	.tsw_outwakeup	= uart_opal_ttyoutwakeup,
 };
 
+static struct {
+	char tmpbuf[16];
+	uint64_t size;
+	struct mtx mtx;
+} escapehatch;
+
+static void
+uart_opal_real_map_outbuffer(uint64_t *bufferp, uint64_t *lenp)
+{
+
+	if (!mtx_initialized(&escapehatch.mtx))
+		mtx_init(&escapehatch.mtx, "uart_opal", NULL, MTX_SPIN | MTX_QUIET |
+		    MTX_NOWITNESS);
+
+	if (!pmap_bootstrapped)
+		return;
+
+	if (TD_IS_IDLETHREAD(curthread)) {
+		escapehatch.size = *(uint64_t *)(*lenp) =
+		    min(sizeof(escapehatch.tmpbuf), *(uint64_t *)(*lenp));
+		mtx_lock_spin(&escapehatch.mtx);
+		memcpy(escapehatch.tmpbuf, (void *)(*bufferp), *(uint64_t *)(*lenp));
+		*bufferp = (uint64_t)escapehatch.tmpbuf;
+		*lenp = (uint64_t)&escapehatch.size;
+	}
+
+	*bufferp = vtophys(*bufferp);
+	*lenp = vtophys(*lenp);
+}
+	
+static void
+uart_opal_real_unmap_outbuffer(uint64_t lenp, uint64_t *origlen)
+{
+
+	if (!pmap_bootstrapped || !TD_IS_IDLETHREAD(curthread))
+		return;
+
+	mtx_assert(&escapehatch.mtx, MA_OWNED);
+	*origlen = escapehatch.size;
+	mtx_unlock_spin(&escapehatch.mtx);
+}
+
 static int
 uart_opal_probe_node(struct uart_opal_softc *sc)
 {
@@ -231,6 +275,7 @@ uart_opal_attach(device_t dev)
 	    MTX_SPIN | MTX_QUIET | MTX_NOWITNESS);
 
 	if (console_sc != NULL && console_sc->vtermid == sc->vtermid) {
+		device_printf(dev, "console\n");
 		sc->outseqno = console_sc->outseqno;
 		console_sc = sc;
 		sprintf(uart_opal_consdev.cn_name, "ttyu%r", unit);
@@ -332,25 +377,20 @@ static int
 uart_opal_put(struct uart_opal_softc *sc, void *buffer, size_t bufsize)
 {
 	uint16_t seqno;
-	uint64_t len = bufsize;
+	uint64_t len;
 	char	cbuf[16];
 	int	err;
 	uint64_t olen = (uint64_t)&len;
 	uint64_t obuf = (uint64_t)cbuf;
 
-	if (pmap_bootstrapped)
-		olen = vtophys(&len);
-
 	if (sc->protocol == OPAL_RAW) {
-		if (pmap_bootstrapped)
-			obuf = vtophys(buffer);
-		else
-			obuf = (uint64_t)(buffer);
+		obuf = (uint64_t)buffer;
+		len = bufsize;
 
+		uart_opal_real_map_outbuffer(&obuf, &olen);
 		err = opal_call(OPAL_CONSOLE_WRITE, sc->vtermid, olen, obuf);
+		uart_opal_real_unmap_outbuffer(olen, &len);
 	} else {
-		if (pmap_bootstrapped)
-			obuf = vtophys(cbuf);
 		uart_lock(&sc->sc_mtx);
 		if (bufsize > 12)
 			bufsize = 12;
@@ -361,7 +401,11 @@ uart_opal_put(struct uart_opal_softc *sc, void *buffer
 		cbuf[3] = seqno & 0xff;
 		memcpy(&cbuf[4], buffer, bufsize);
 		len = 4 + bufsize;
+
+		uart_opal_real_map_outbuffer(&obuf, &olen);
 		err = opal_call(OPAL_CONSOLE_WRITE, sc->vtermid, olen, obuf);
+		uart_opal_real_unmap_outbuffer(olen, &len);
+
 		uart_unlock(&sc->sc_mtx);
 
 		len -= 4;