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Subjectbcm2711_thermal: Kernel panic - not syncing: Asynchronous SError Interrupt
Trying to dump the BCM2711 registers kills the kernel:

# cat /sys/kernel/debug/regmap/dummy-avs-monitor\@fd5d2000/range
0-efc
# cat /sys/kernel/debug/regmap/dummy-avs-monitor\@fd5d2000/registers

[ 62.857661] SError Interrupt on CPU1, code 0xbf000002 -- SError
[ 62.857671] CPU: 1 PID: 478 Comm: cat Not tainted 5.11.0-rc7 #4
[ 62.857674] Hardware name: Raspberry Pi 4 Model B Rev 1.2 (DT)
[ 62.857676] pstate: 20000085 (nzCv daIf -PAN -UAO -TCO BTYPE=--)
[ 62.857679] pc : regmap_mmio_read32le+0x1c/0x34
[ 62.857681] lr : regmap_mmio_read+0x50/0x80
[ 62.857682] sp : ffff8000105c3c00
[ 62.857685] x29: ffff8000105c3c00 x28: 0000000000000014
[ 62.857694] x27: 0000000000000014 x26: ffffd2ea1c2060b0
[ 62.857699] x25: ffff4e34408ecc00 x24: 0000000000000efc
[ 62.857704] x23: ffff8000105c3e20 x22: ffff8000105c3d3c
[ 62.857710] x21: ffff8000105c3d3c x20: 0000000000000014
[ 62.857715] x19: ffff4e344037a900 x18: 0000000000000020
[ 62.857720] x17: 0000000000000000 x16: 0000000000000000
[ 62.857725] x15: ffff4e3447ac40f0 x14: 0000000000000003
[ 62.857730] x13: ffff4e34422c0000 x12: ffff4e34422a0046
[ 62.857735] x11: ffffd2ea1c8765e0 x10: 0000000000000000
[ 62.857741] x9 : ffffd2ea1b9495a0 x8 : ffff4e34429ef980
[ 62.857746] x7 : 000000000000000f x6 : ffff4e34422a004b
[ 62.857751] x5 : 00000000fffffff9 x4 : 0000000000000000
[ 62.857757] x3 : ffffd2ea1b949550 x2 : ffffd2ea1b949330
[ 62.857761] x1 : 0000000000000014 x0 : 0000000000000000
[ 62.857767] Kernel panic - not syncing: Asynchronous SError Interrupt
[ 62.857770] CPU: 1 PID: 478 Comm: cat Not tainted 5.11.0-rc7 #4
[ 62.857773] Hardware name: Raspberry Pi 4 Model B Rev 1.2 (DT)
[ 62.857775] Call trace:
[ 62.857777] dump_backtrace+0x0/0x1e0
[ 62.857778] show_stack+0x24/0x70
[ 62.857780] dump_stack+0xd0/0x12c
[ 62.857782] panic+0x168/0x370
[ 62.857783] nmi_panic+0x98/0xa0
[ 62.857786] arm64_serror_panic+0x8c/0x98
[ 62.857787] do_serror+0x3c/0x6c
[ 62.857789] el1_error+0x78/0xf0
[ 62.857791] regmap_mmio_read32le+0x1c/0x34
[ 62.857793] _regmap_bus_reg_read+0x24/0x30
[ 62.857795] _regmap_read+0x6c/0x17c
[ 62.857797] regmap_read+0x58/0x84
[ 62.857799] regmap_read_debugfs+0x138/0x3f4
[ 62.857801] regmap_map_read_file+0x34/0x40
[ 62.857803] full_proxy_read+0x6c/0xc0
[ 62.857805] vfs_read+0xb8/0x1e4
[ 62.857807] ksys_read+0x78/0x10c
[ 62.857809] __arm64_sys_read+0x28/0x34
[ 62.857811] el0_svc_common.constprop.0+0x7c/0x194
[ 62.857813] do_el0_svc+0x30/0x9c
[ 62.857814] el0_svc+0x20/0x30
[ 62.857816] el0_sync_handler+0x1a4/0x1b0
[ 62.857818] el0_sync+0x174/0x180
[ 62.857842] SMP: stopping secondary CPUs
[ 62.857845] Kernel Offset: 0x52ea0b080000 from 0xffff800010000000
[ 62.857847] PHYS_OFFSET: 0xffffb1cc00000000
[ 62.857849] CPU features: 0x00240022,61806000
[ 62.857851] Memory Limit: none

Sprinkling printks around regmap_read [1] shows that reading from 0x14 (20)
seems to cause the issue:


[ 40.456230] map=ffff020a069c9c00, from=0, to=3836, count=131072
[ 40.462520] map=ffff020a069c9c00, i=0
[ 40.466319] ret=0, val=0
[ 40.468922] map=ffff020a069c9c00, i=4
[ 40.472684] ret=0, val=0
[ 40.475292] map=ffff020a069c9c00, i=8
[ 40.479048] ret=0, val=0
[ 40.481649] map=ffff020a069c9c00, i=12
[ 40.485492] ret=0, val=0
[ 40.488080] map=ffff020a069c9c00, i=16
[ 40.491922] ret=0, val=0
[ 40.494523] map=ffff020a069c9c00, i=20
[ 40.498497] SError Interrupt on CPU0, code 0xbf000002 -- SError
[ 40.498499] CPU: 0 PID: 486 Comm: cat Not tainted 5.11.0-rc7+ #8
[ 40.498501] Hardware name: Raspberry Pi 4 Model B Rev 1.2 (DT)


...Juerg

[1]
diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index ff2ee87987c7..9465f5a2f3b8 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -229,6 +229,7 @@ static ssize_t regmap_read_debugfs(struct regmap *map, unsigned int from,
if (count > (PAGE_SIZE << (MAX_ORDER - 1)))
count = PAGE_SIZE << (MAX_ORDER - 1);

+ printk("map=%px, from=%d, to=%d, count=%ld\n", map, from, to, count);
buf = kmalloc(count, GFP_KERNEL);
if (!buf)
return -ENOMEM;
@@ -253,7 +254,9 @@ static ssize_t regmap_read_debugfs(struct regmap *map, unsigned int from,
buf_pos += map->debugfs_reg_len + 2;

/* Format the value, write all X if we can't read */
+ printk("map=%px, i=%d\n", map, i);
ret = regmap_read(map, i, &val);
+ printk("ret=%ld, val=%x\n", ret, val);
if (ret == 0)
snprintf(buf + buf_pos, count - buf_pos,
"%.*x", map->debugfs_val_len, val);
[unhandled content-type:application/pgp-signature]
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