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Subject[PATCH] irqchip/irq-mtk-sysirq: drop unnecessary spinlock
Date
From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

This driver takes a regular spinlock when a raw spinlock is already
taken which results in the following lockdep splat:

=============================
[ BUG: Invalid wait context ]
5.7.0-rc6-02446-gb9827c0a9fe7-dirty #1 Not tainted
-----------------------------
swapper/0/0 is trying to lock:
ffffff800303b798 (&chip_data->lock){....}-{3:3}, at: mtk_sysirq_set_type+0x48/0xc0
other info that might help us debug this:
context-{5:5}
2 locks held by swapper/0/0:
#0: ffffff800302ee68 (&desc->request_mutex){....}-{4:4}, at: __setup_irq+0xc4/0x8a0
#1: ffffff800302ecf0 (&irq_desc_lock_class){....}-{2:2}, at: __setup_irq+0xe4/0x8a0
stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.7.0-rc6-02446-gb9827c0a9fe7-dirty #1
Hardware name: Pumpkin MT8516 (DT)
Call trace:
dump_backtrace+0x0/0x180
show_stack+0x14/0x20
dump_stack+0xd0/0x118
__lock_acquire+0x8c8/0x2270
lock_acquire+0xf8/0x470
_raw_spin_lock_irqsave+0x50/0x78
mtk_sysirq_set_type+0x48/0xc0
__irq_set_trigger+0x58/0x170
__setup_irq+0x420/0x8a0
request_threaded_irq+0xd8/0x190
timer_of_init+0x1e8/0x2c4
mtk_gpt_init+0x5c/0x1dc
timer_probe+0x74/0xf4
time_init+0x14/0x44
start_kernel+0x394/0x4f0

We don't need the spinlock here - the irq_set_type() callback is always
called with the irq_desc->lock taken. This removes the spinlock entirely.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/irqchip/irq-mtk-sysirq.c | 6 ------
1 file changed, 6 deletions(-)

diff --git a/drivers/irqchip/irq-mtk-sysirq.c b/drivers/irqchip/irq-mtk-sysirq.c
index 73eae5966a40..da2fc4809222 100644
--- a/drivers/irqchip/irq-mtk-sysirq.c
+++ b/drivers/irqchip/irq-mtk-sysirq.c
@@ -12,10 +12,8 @@
#include <linux/of_address.h>
#include <linux/io.h>
#include <linux/slab.h>
-#include <linux/spinlock.h>

struct mtk_sysirq_chip_data {
- spinlock_t lock;
u32 nr_intpol_bases;
void __iomem **intpol_bases;
u32 *intpol_words;
@@ -30,14 +28,12 @@ static int mtk_sysirq_set_type(struct irq_data *data, unsigned int type)
u8 intpol_idx = chip_data->intpol_idx[hwirq];
void __iomem *base;
u32 offset, reg_index, value;
- unsigned long flags;
int ret;

base = chip_data->intpol_bases[intpol_idx];
reg_index = chip_data->which_word[hwirq];
offset = hwirq & 0x1f;

- spin_lock_irqsave(&chip_data->lock, flags);
value = readl_relaxed(base + reg_index * 4);
if (type == IRQ_TYPE_LEVEL_LOW || type == IRQ_TYPE_EDGE_FALLING) {
if (type == IRQ_TYPE_LEVEL_LOW)
@@ -53,7 +49,6 @@ static int mtk_sysirq_set_type(struct irq_data *data, unsigned int type)

data = data->parent_data;
ret = data->chip->irq_set_type(data, type);
- spin_unlock_irqrestore(&chip_data->lock, flags);
return ret;
}

@@ -212,7 +207,6 @@ static int __init mtk_sysirq_of_init(struct device_node *node,
ret = -ENOMEM;
goto out_free_which_word;
}
- spin_lock_init(&chip_data->lock);

return 0;

--
2.25.0
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