From b8bc6b7954e27edb449503004ef52b8b97585545 Mon Sep 17 00:00:00 2001
From: Alfredo Dal'Ava Junior <alfredo@FreeBSD.org>
Date: Fri, 16 Apr 2021 19:51:15 -0300
Subject: [PATCH] opal_console: fix serial console output corruption on
 powerpc64

Adds OPAL_CONSOLE_WRITE error handling and implements a call to
OPAL_CONSOLE_WRITE_BUFFER_SPACE to verify if there's enough space
before writing to console.

This fixes serial port output getting corrupted on fast writes, like
on "dmesg" output.

Tested on Raptor Blackbird running powerpc64 BE kernel

Reviewed by:	luporl
Sponsored by:	Eldorado Reserach Institute (eldorado.org.br)
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D29063
---
 sys/powerpc/powernv/opal.h         |  1 +
 sys/powerpc/powernv/opal_console.c | 49 +++++++++++++++++++++++++-----
 2 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/sys/powerpc/powernv/opal.h b/sys/powerpc/powernv/opal.h
index d7a81e33f809..8e39a39b6c9a 100644
--- a/sys/powerpc/powernv/opal.h
+++ b/sys/powerpc/powernv/opal.h
@@ -56,6 +56,7 @@ int opal_call(uint64_t token, ...);
 #define	OPAL_PCI_CONFIG_WRITE_HALF_WORD	17
 #define	OPAL_PCI_CONFIG_WRITE_WORD	18
 #define	OPAL_PCI_EEH_FREEZE_STATUS	23
+#define OPAL_CONSOLE_WRITE_BUFFER_SPACE 25
 #define	OPAL_PCI_EEH_FREEZE_CLEAR	26
 #define	OPAL_PCI_PHB_MMIO_ENABLE	27
 #define	OPAL_PCI_SET_PHB_MEM_WINDOW	28
diff --git a/sys/powerpc/powernv/opal_console.c b/sys/powerpc/powernv/opal_console.c
index 7b953d2679fb..8f6c88f81f7c 100644
--- a/sys/powerpc/powernv/opal_console.c
+++ b/sys/powerpc/powernv/opal_console.c
@@ -171,6 +171,24 @@ uart_opal_real_unmap_outbuffer(uint64_t *len)
 	mtx_unlock_spin(&opalcons_buffer.mtx);
 }
 
+static int64_t
+uart_opal_console_write_buffer_space(int vtermid)
+{
+	int64_t buffer_space_val = 0;
+	vm_paddr_t buffer_space_ptr;
+
+	if (pmap_bootstrapped)
+		buffer_space_ptr = vtophys(&buffer_space_val);
+	else
+		buffer_space_ptr = (vm_paddr_t)&buffer_space_val;
+
+	if (opal_call(OPAL_CONSOLE_WRITE_BUFFER_SPACE, vtermid,
+	    buffer_space_ptr) != OPAL_SUCCESS)
+		return (-1);
+
+	return (be64toh(buffer_space_val));
+}
+
 static int
 uart_opal_probe_node(struct uart_opal_softc *sc)
 {
@@ -420,12 +438,12 @@ uart_opal_put(struct uart_opal_softc *sc, void *buffer, size_t bufsize)
 		len -= 4;
 	}
 
-#if 0
-	if (err != OPAL_SUCCESS)
-		len = 0;
-#endif
+	if (err == OPAL_SUCCESS)
+		return (len);
+	else if (err == OPAL_BUSY_EVENT)
+		return(0);
 
-	return (len);
+	return (-1);
 }
 
 static int
@@ -481,11 +499,28 @@ uart_opal_ttyoutwakeup(struct tty *tp)
 	struct uart_opal_softc *sc;
 	char buffer[8];
 	int len;
+	int64_t buffer_space;
 
 	sc = tty_softc(tp);
 
-	while ((len = ttydisc_getc(tp, buffer, sizeof(buffer))) != 0)
-		uart_opal_put(sc, buffer, len);
+	while ((len = ttydisc_getc(tp, buffer, sizeof(buffer))) != 0) {
+		int bytes_written = 0;
+		while (bytes_written == 0) {
+			buffer_space = uart_opal_console_write_buffer_space(sc->vtermid);
+			if (buffer_space == -1)
+				/* OPAL failure or invalid terminal */
+				break;
+			else if (buffer_space >= len)
+				bytes_written = uart_opal_put(sc, buffer, len);
+
+			if (bytes_written == 0)
+				/* OPAL must be busy, poll and retry */
+				opal_call(OPAL_POLL_EVENTS, NULL);
+			else if (bytes_written == -1)
+				/* OPAL failure or invalid terminal */
+				break;
+		}
+	}
 }
 
 static void