From 416f25a948d11ef15733f2e31658d31b5cc7bef6 Mon Sep 17 00:00:00 2001 From: Thomas Nixon Date: Sun, 26 Mar 2023 11:08:49 +0100 Subject: [PATCH] mtd: rawnand: xway: don't yield while holding spinlock The nand driver normally while waiting for the device to become ready; this is normally fine, but xway_nand holds the ebu_lock spinlock, and this can cause lockups if other threads which use ebu_lock are interleaved. Fix this by waiting instead of polling. This mainly showed up as crashes in ath9k_pci_owl_loader (see https://github.com/openwrt/openwrt/issues/9829 ), but turning on spinlock debugging shows this happening in other places too. This doesn't seem to measurably impact boot time. Signed-off-by: Thomas Nixon --- drivers/mtd/nand/raw/xway_nand.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/drivers/mtd/nand/raw/xway_nand.c +++ b/drivers/mtd/nand/raw/xway_nand.c @@ -176,7 +176,13 @@ static void xway_cmd_ctrl(struct nand_ch static int xway_dev_ready(struct nand_chip *chip) { - return ltq_ebu_r32(EBU_NAND_WAIT) & NAND_WAIT_RD; + /* + * wait until ready, as otherwise the driver will yield in nand_wait or + * nand_wait_ready, which is a bad idea when we're holding ebu_lock + */ + while ((ltq_ebu_r32(EBU_NAND_WAIT) & NAND_WAIT_RD) == 0) + cpu_relax(); + return 1; } static unsigned char xway_read_byte(struct nand_chip *chip)