From: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>
[ Upstream commit 1ed9b927e7dd8b8cff13052efe212a8ff72ec51d ]
In some cases when using the maple tree register cache, the lockdep
validator might complain about invalid deadlocks:
[7.131886] Possible interrupt unsafe locking scenario:
[7.131890] CPU0 CPU1
[7.131893] ---- ----
[7.131896] lock(&mt->ma_lock);
[7.131904] local_irq_disable();
[7.131907] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock);
[7.131916] lock(&mt->ma_lock);
[7.131925] <Interrupt>
[7.131928] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock);
[7.131936]
*** DEADLOCK ***
[7.131939] no locks held by swapper/0/0.
[7.131944]
the shortest dependencies between 2nd lock and 1st lock:
[7.131950] -> (&mt->ma_lock){+.+.}-{2:2} {
[7.131966] HARDIRQ-ON-W at:
[7.131973] lock_acquire+0x200/0x330
[7.131986] _raw_spin_lock+0x50/0x70
[7.131998] regcache_maple_write+0x68/0xe0
[7.132010] regcache_write+0x6c/0x90
[7.132019] _regmap_read+0x19c/0x1d0
[7.132029] _regmap_update_bits+0xc0/0x148
[7.132038] regmap_update_bits_base+0x6c/0xa8
[7.132048] rk8xx_probe+0x22c/0x3d8
[7.132057] rk8xx_spi_probe+0x74/0x88
[7.132065] spi_probe+0xa8/0xe0
[...]
[7.132675] }
[7.132678] ... key at: [<ffff800082943c20>] __key.0+0x0/0x10
[7.132691] ... acquired at:
[7.132695] _raw_spin_lock+0x50/0x70
[7.132704] regcache_maple_write+0x68/0xe0
[7.132714] regcache_write+0x6c/0x90
[7.132724] _regmap_read+0x19c/0x1d0
[7.132732] _regmap_update_bits+0xc0/0x148
[7.132741] regmap_field_update_bits_base+0x74/0xb8
[7.132751] vop2_plane_atomic_update+0x480/0x14d8 [rockchipdrm]
[7.132820] drm_atomic_helper_commit_planes+0x1a0/0x320 [drm_kms_helper]
[...]
[7.135112] -> (rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock){-...}-{2:2} {
[7.135130] IN-HARDIRQ-W at:
[7.135136] lock_acquire+0x200/0x330
[7.135147] _raw_spin_lock_irqsave+0x6c/0x98
[7.135157] regmap_lock_spinlock+0x20/0x40
[7.135166] regmap_read+0x44/0x90
[7.135175] vop2_isr+0x90/0x290 [rockchipdrm]
[7.135225] __handle_irq_event_percpu+0x124/0x2d0
In the example above, the validator seems to get the scope of
dependencies wrong, since the regmap instance used in rk8xx-spi driver
has nothing to do with the instance from vop2.
Improve validation by sharing the regmap's lockdep class with the maple
tree's internal lock, while also providing a subclass for the latter.
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>
Link: https://patch.msgid.link/20241031-regmap-maple-lockdep-fix-v2-1-06a3710f3623@xxxxxxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/base/regmap/internal.h | 1 +
drivers/base/regmap/regcache-maple.c | 3 +++
drivers/base/regmap/regmap.c | 1 +
3 files changed, 5 insertions(+)
diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 9a9ea514c2d81..a29f24b15928c 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -59,6 +59,7 @@ struct regmap {
unsigned long raw_spinlock_flags;
};
};
+ struct lock_class_key *lock_key;
regmap_lock lock;
regmap_unlock unlock;
void *lock_arg; /* This is passed to lock/unlock functions */
diff --git a/drivers/base/regmap/regcache-maple.c b/drivers/base/regmap/regcache-maple.c
index 0b6c2277128b4..fb5761a5ef6ee 100644
--- a/drivers/base/regmap/regcache-maple.c
+++ b/drivers/base/regmap/regcache-maple.c
@@ -356,6 +356,9 @@ static int regcache_maple_init(struct regmap *map)
mt_init(mt);
+ if (!mt_external_lock(mt) && map->lock_key)
+ lockdep_set_class_and_subclass(&mt->ma_lock, map->lock_key, 1);
+
if (!map->num_reg_defaults)
return 0;
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index c5b5241891a5a..1f17c6816850c 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -745,6 +745,7 @@ struct regmap *__regmap_init(struct device *dev,
lock_key, lock_name);
}
map->lock_arg = map;
+ map->lock_key = lock_key;
}
/*
--
2.43.0
