[Skiboot] [PATCH 2/2] FSP: Introduce busy flag in fsp_fetch_data

[Vasant Hegde]

Use busy flag to avoid multiple processors trying to fetch
at the same time and colliding on the TCE space.

With this patch we don't hold fsp_fetch_lock before entering
opal_run_pollers. Fixes "Running pollers with lock held" issue
as well.

Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
---
Ben,
  If you are fine with this, I will fix capp_lid_download() as well.

-Vasant

 hw/fsp/fsp.c |   43 +++++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/hw/fsp/fsp.c b/hw/fsp/fsp.c
index fdf175a..0ab4a56 100644
--- a/hw/fsp/fsp.c
+++ b/hw/fsp/fsp.c
@@ -2142,14 +2142,13 @@ uint32_t fsp_adjust_lid_side(uint32_t lid_no)
 	return lid_no;
 }
 
-int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
-		   uint32_t offset, void *buffer, size_t *length)
+static int __fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
+			    uint32_t offset, void *buffer, size_t *length)
 {
 	uint32_t total, remaining = *length;
 	uint64_t baddr;
 	uint64_t balign, boff, bsize;
 	struct fsp_msg *msg;
-	static struct lock fsp_fetch_lock = LOCK_UNLOCKED;
 
 	*length = total = 0;
 
@@ -2160,11 +2159,6 @@ int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
 	      "(0x%x bytes)\n",
 	      id, sub_id, buffer, remaining);
 
-	/*
-	 * Use a lock to avoid multiple processors trying to fetch
-	 * at the same time and colliding on the TCE space
-	 */
-	lock(&fsp_fetch_lock);
 
 	while(remaining) {
 		uint32_t chunk, taddr, woffset, wlen;
@@ -2201,7 +2195,6 @@ int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
 
 		/* XXX Is flash busy (0x3f) a reason for retry ? */
 		if (rc != 0 && rc != 2) {
-			unlock(&fsp_fetch_lock);
 			return -EIO;
 		}
 
@@ -2218,7 +2211,6 @@ int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
 		if (wlen < chunk)
 			break;
 	}
-	unlock(&fsp_fetch_lock);
 
 	*length = total;
 
@@ -2226,6 +2218,37 @@ int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
 }
 
 /*
+ * Use busy flag to avoid multiple processors trying to fetch
+ * at the same time and colliding on the TCE space
+ */
+int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
+		   uint32_t offset, void *buffer, size_t *length)
+{
+	static bool fetch_data_busy = false;
+	int rc;
+	static struct lock fsp_fetch_lock = LOCK_UNLOCKED;
+
+	for (;;) {
+		lock(&fsp_fetch_lock);
+		if (!fetch_data_busy) {
+			fetch_data_busy = true;
+			unlock(&fsp_fetch_lock);
+			break;
+		}
+		unlock(&fsp_fetch_lock);
+		cpu_relax();
+	}
+
+	rc = __fsp_fetch_data(flags, id, sub_id, offset, buffer, length);
+
+	lock(&fsp_fetch_lock);
+	fetch_data_busy = false;
+	unlock(&fsp_fetch_lock);
+
+	return rc;
+}
+
+/*
  * Asynchronous fsp fetch data call
  *
  * Note: