mtd: rawnand: brcmnand: Fix crash during the panic_write

When executing a NAND command within the panic write path, wait for any
pending command instead of calling BUG_ON to avoid crashing while
already crashing.

Fixes: 27c5b17c ("mtd: nand: add NAND driver "library" for Broadcom STB NAND controller")
Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Kursad Oney <kursad.oney@broadcom.com>
Reviewed-by: Kamal Dasu <kamal.dasu@broadcom.com>
Cc: stable@vger.kernel.org
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230706182909.79151-4-william.zhang@broadcom.com

drivers/mtd/nand/raw/brcmnand/brcmnand.c

@@ -1608,7 +1608,17 @@ static void brcmnand_send_cmd(struct brcmnand_host *host, int cmd)
 
 	dev_dbg(ctrl->dev, "send native cmd %d addr 0x%llx\n", cmd, cmd_addr);
 
-	BUG_ON(ctrl->cmd_pending != 0);
+	/*
+	 * If we came here through _panic_write and there is a pending
+	 * command, try to wait for it. If it times out, rather than
+	 * hitting BUG_ON, just return so we don't crash while crashing.
+	 */
+	if (oops_in_progress) {
+		if (ctrl->cmd_pending &&
+			bcmnand_ctrl_poll_status(ctrl, NAND_CTRL_RDY, NAND_CTRL_RDY, 0))
+			return;
+	} else
+		BUG_ON(ctrl->cmd_pending != 0);
 	ctrl->cmd_pending = cmd;
 
 	ret = bcmnand_ctrl_poll_status(ctrl, NAND_CTRL_RDY, NAND_CTRL_RDY, 0);