[Skiboot] [PATCH v2] opal/fsp: Fix opal boot failure on systems with redundant FSP

[Mahesh Salgaonkar]

On systems with redundant FSP, opal detects primary/backup FSPs.
However, it ends up considering Backup FSP as active_fsp and starts
mailbox communication with it. This causes opal to send IPL messages to
backup FSP instead of primary. Since primary FSP never receives IPL
messages from OPAL, it assumes that opal failed to boot and enters into
termination state.

The active_fsp is set during fsp_update_links_states() function which is
invoked during boot, through fsp_create_fsp(), as well as reset/reload,
through fsp_reinit_fsp(). During the boot, when 2 FSPs are detected by
opal, fsp_update_links_states() sets the last one as active_fsp which
may not be primary FSP.

Fix this issue by detecting/setting primary FSP as active_fsp during
opal boot.

Signed-off-by: Mahesh Salgaonkar <mahesh at linux.ibm.com>
---
Change in v2:
- Set active_fsp unconditionally in fsp_update_links_states()
- See v1 at https://lists.ozlabs.org/pipermail/skiboot/2025-March/019152.html
---
 hw/fsp/fsp.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/hw/fsp/fsp.c b/hw/fsp/fsp.c
index 2fd9e5f05..a4a95520b 100644
--- a/hw/fsp/fsp.c
+++ b/hw/fsp/fsp.c
@@ -76,6 +76,7 @@ struct fsp {
 	unsigned int		iopath_count;
 	int			active_iopath;	/* -1: no active IO path */
 	struct fsp_iopath	iopath[FSP_MAX_IOPATH];
+	bool			primary;
 };
 
 enum ipl_state {
@@ -1959,8 +1960,21 @@ static void fsp_update_links_states(struct fsp *fsp)
 	}
 
 	if (fsp->active_iopath >= 0) {
-		if (!active_fsp || (active_fsp != fsp))
-			active_fsp = fsp;
+
+		/*
+		 * Set active_fsp unconditionally to active FSP.
+		 *
+		 * fsp_update_links_states() function is invoked during boot as
+		 * well as FSP reset/reload. During boot, when 2 FSPs are
+		 * detected by opal it will select the last one as active_fsp
+		 * which may not be primary. But that is ok, during boot once
+		 * we are done discovering all FSPs we will set primary FSP as
+		 * active_fsp through fsp_init_set_active() function.
+		 *
+		 * In reset/reload path, we will go over list of all FSPs and
+		 * set one which has active link. see fsp_reinit_fsp().
+		 */
+		active_fsp = fsp;
 
 		fsp_inbound_off = 0;
 		fiop = &fsp->iopath[fsp->active_iopath];
@@ -2003,8 +2017,12 @@ static void fsp_create_fsp(struct dt_node *fsp_node)
 	fsp->index = index;
 	fsp->active_iopath = -1;
 
+	if (dt_find_property(fsp_node, "primary"))
+		fsp->primary = true;
+
 	count = linksprop->len / 4;
-	prlog(PR_DEBUG, "FSP #%d: Found %d IO PATH\n", index, count);
+	prlog(PR_DEBUG, "FSP #%d: Found %d IO PATH %s\n", index, count,
+			fsp->primary ? "(Primary FSP)" : "");
 	if (count > FSP_MAX_IOPATH) {
 		prerror("FSP #%d: WARNING, limited to %d IO PATH\n",
 			index, FSP_MAX_IOPATH);
@@ -2073,6 +2091,16 @@ int fsp_fatal_msg(struct fsp_msg *msg)
 	return rc;
 }
 
+static void fsp_init_set_active(void)
+{
+	struct fsp *fsp;
+
+	/* Mark primary FSP as active fsp during boot */
+	for (fsp = first_fsp; fsp; fsp = fsp->link)
+		if (fsp->primary)
+			active_fsp = fsp;
+}
+
 static bool fsp_init_one(const char *compat)
 {
 	struct dt_node *fsp_node;
@@ -2104,6 +2132,7 @@ static bool fsp_init_one(const char *compat)
 		/* Create the FSP data structure */
 		fsp_create_fsp(fsp_node);
 	}
+	fsp_init_set_active();
 
 	return inited;
 }
-- 
2.49.0