libflash/ipmi-hiomap: Restore window state on window/protocol reset

The initial implementation of ipmi-hiomap left a bit to be desired when
it came to event handling: it didn't completely restore the state of the
system to what it was before events like a hiomap protocol or window
reset take place. The result is the host cannot recover from e.g. the
BMC being rebooted underneath it.

Take the only step required in the event of window reset, or the final
step after performing the handshake in the event of a protocol reset,
and re-open the previously active window if there was one.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

libflash/ipmi-hiomap.c

@@ -561,6 +561,29 @@ static int lpc_window_write(struct ipmi_hiomap *ctx, uint32_t pos,
 	return 0;
 }
 
+/* Try to restore the window state */
+static bool ipmi_hiomap_restore_window(struct ipmi_hiomap *ctx)
+{
+	uint64_t size;
+	uint8_t cmd;
+
+	lock(&ctx->lock);
+	if (ctx->window_state == closed_window) {
+		unlock(&ctx->lock);
+		return true;
+	}
+
+	cmd = ctx->window_state == read_window ?
+		HIOMAP_C_CREATE_READ_WINDOW :
+		HIOMAP_C_CREATE_WRITE_WINDOW;
+
+	ctx->window_state = closed_window;
+	unlock(&ctx->lock);
+
+	return hiomap_window_move(ctx, cmd, ctx->current.cur_pos,
+				  ctx->current.size, &size);
+}
+
 /* Best-effort asynchronous event handling by blocklevel callbacks */
 static int ipmi_hiomap_handle_events(struct ipmi_hiomap *ctx)
 {
@@ -599,6 +622,8 @@ static int ipmi_hiomap_handle_events(struct ipmi_hiomap *ctx)
 	}
 
 	if (status & HIOMAP_E_PROTOCOL_RESET) {
+		prlog(PR_INFO, "Protocol was reset\n");
+
 		if (!hiomap_get_info(ctx)) {
 			prerror("Failure to renegotiate after protocol reset\n");
 			return FLASH_ERR_DEVICE_GONE;
@@ -609,13 +634,24 @@ static int ipmi_hiomap_handle_events(struct ipmi_hiomap *ctx)
 			return FLASH_ERR_DEVICE_GONE;
 		}
 
-		prlog(PR_INFO, "Renegotiated protocol after reset\n");
-		return FLASH_ERR_AGAIN;
+		if (!ipmi_hiomap_restore_window(ctx)) {
+			prerror("Failure to restore window state after protocol reset\n");
+			return FLASH_ERR_DEVICE_GONE;
+		}
+
+		prlog(PR_INFO, "Restored window state after protocol reset\n");
+		return 0;
 	}
 
 	if (status & HIOMAP_E_WINDOW_RESET) {
 		prlog(PR_INFO, "Window was reset\n");
-		return FLASH_ERR_AGAIN;
+
+		if (!ipmi_hiomap_restore_window(ctx)) {
+			prerror("Failed to restore previous window parameters after protocol reset\n");
+			return FLASH_ERR_DEVICE_GONE;
+		}
+
+		prlog(PR_INFO, "Restored window state after window reset\n");
 	}
 
 	return 0;