[PATCH AUTOSEL 6.18-5.10] gpio: sprd: Change sprd_gpio lock to raw_spin_lock

[Sasha Levin <sashal@kernel.org>]

From: Xuewen Yan <xuewen.yan@unisoc.com>

[ Upstream commit 96313fcc1f062ba239f4832c9eff685da6c51c99 ]

There was a lockdep warning in sprd_gpio:

[    6.258269][T329@C6] [ BUG: Invalid wait context ]
[    6.258270][T329@C6] 6.18.0-android17-0-g30527ad7aaae-ab00009-4k #1 Tainted: G        W  OE
[    6.258272][T329@C6] -----------------------------
[    6.258273][T329@C6] modprobe/329 is trying to lock:
[    6.258275][T329@C6] ffffff8081c91690 (&sprd_gpio->lock){....}-{3:3}, at: sprd_gpio_irq_unmask+0x4c/0xa4 [gpio_sprd]
[    6.258282][T329@C6] other info that might help us debug this:
[    6.258283][T329@C6] context-{5:5}
[    6.258285][T329@C6] 3 locks held by modprobe/329:
[    6.258286][T329@C6]  #0: ffffff808baca108 (&dev->mutex){....}-{4:4}, at: __driver_attach+0xc4/0x204
[    6.258295][T329@C6]  #1: ffffff80965e7240 (request_class#4){+.+.}-{4:4}, at: __setup_irq+0x1cc/0x82c
[    6.258304][T329@C6]  #2: ffffff80965e70c8 (lock_class#4){....}-{2:2}, at: __setup_irq+0x21c/0x82c
[    6.258313][T329@C6] stack backtrace:
[    6.258314][T329@C6] CPU: 6 UID: 0 PID: 329 Comm: modprobe Tainted: G        W  OE       6.18.0-android17-0-g30527ad7aaae-ab00009-4k #1 PREEMPT  3ad5b0f45741a16e5838da790706e16ceb6717df
[    6.258316][T329@C6] Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
[    6.258317][T329@C6] Hardware name: Unisoc UMS9632-base Board (DT)
[    6.258318][T329@C6] Call trace:
[    6.258318][T329@C6]  show_stack+0x20/0x30 (C)
[    6.258321][T329@C6]  __dump_stack+0x28/0x3c
[    6.258324][T329@C6]  dump_stack_lvl+0xac/0xf0
[    6.258326][T329@C6]  dump_stack+0x18/0x3c
[    6.258329][T329@C6]  __lock_acquire+0x824/0x2c28
[    6.258331][T329@C6]  lock_acquire+0x148/0x2cc
[    6.258333][T329@C6]  _raw_spin_lock_irqsave+0x6c/0xb4
[    6.258334][T329@C6]  sprd_gpio_irq_unmask+0x4c/0xa4 [gpio_sprd 814535e93c6d8e0853c45c02eab0fa88a9da6487]
[    6.258337][T329@C6]  irq_startup+0x238/0x350
[    6.258340][T329@C6]  __setup_irq+0x504/0x82c
[    6.258342][T329@C6]  request_threaded_irq+0x118/0x184
[    6.258344][T329@C6]  devm_request_threaded_irq+0x94/0x120
[    6.258347][T329@C6]  sc8546_init_irq+0x114/0x170 [sc8546_charger 223586ccafc27439f7db4f95b0c8e6e882349a99]
[    6.258352][T329@C6]  sc8546_charger_probe+0x53c/0x5a0 [sc8546_charger 223586ccafc27439f7db4f95b0c8e6e882349a99]
[    6.258358][T329@C6]  i2c_device_probe+0x2c8/0x350
[    6.258361][T329@C6]  really_probe+0x1a8/0x46c
[    6.258363][T329@C6]  __driver_probe_device+0xa4/0x10c
[    6.258366][T329@C6]  driver_probe_device+0x44/0x1b4
[    6.258369][T329@C6]  __driver_attach+0xd0/0x204
[    6.258371][T329@C6]  bus_for_each_dev+0x10c/0x168
[    6.258373][T329@C6]  driver_attach+0x2c/0x3c
[    6.258376][T329@C6]  bus_add_driver+0x154/0x29c
[    6.258378][T329@C6]  driver_register+0x70/0x10c
[    6.258381][T329@C6]  i2c_register_driver+0x48/0xc8
[    6.258384][T329@C6]  init_module+0x28/0xfd8 [sc8546_charger 223586ccafc27439f7db4f95b0c8e6e882349a99]
[    6.258389][T329@C6]  do_one_initcall+0x128/0x42c
[    6.258392][T329@C6]  do_init_module+0x60/0x254
[    6.258395][T329@C6]  load_module+0x1054/0x1220
[    6.258397][T329@C6]  __arm64_sys_finit_module+0x240/0x35c
[    6.258400][T329@C6]  invoke_syscall+0x60/0xec
[    6.258402][T329@C6]  el0_svc_common+0xb0/0xe4
[    6.258405][T329@C6]  do_el0_svc+0x24/0x30
[    6.258407][T329@C6]  el0_svc+0x54/0x1c4
[    6.258409][T329@C6]  el0t_64_sync_handler+0x68/0xdc
[    6.258411][T329@C6]  el0t_64_sync+0x1c4/0x1c8

This is because the spin_lock would change to rt_mutex in PREEMPT_RT,
however the sprd_gpio->lock would use in hard-irq, this is unsafe.

So change the spin_lock_t to raw_spin_lock_t to use the spinlock
in hard-irq.

Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20260126094209.9855-1-xuewen.yan@unisoc.com
[Bartosz: tweaked the commit message]
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

The driver has been present since kernel 4.14 (initial commit
`9a3821c2bb47d`). The patch should apply cleanly to all stable versions
as it's a simple lock type change with no dependencies.

### 9. SIMILAR PRECEDENT

This type of fix (spin_lock → raw_spin_lock for RT compatibility in IRQ
context) is extremely common and well-understood. It's a standard
pattern that has been applied to many drivers.

### SUMMARY

**Pros:**
- Fixes a real lockdep warning/bug on PREEMPT_RT systems
- Very small, mechanical, and obviously correct change
- Reviewed by PREEMPT_RT maintainer (Sebastian Andrzej Siewior)
- No functional change on non-RT kernels
- Pattern has been applied many times before
- Clean backport - no dependencies

**Cons:**
- Affects only PREEMPT_RT users (smaller user base)
- The driver is for Spreadtrum/Unisoc hardware (embedded/mobile)

**Risk vs Benefit:**
- Risk: Negligible - the change is mechanical and well-understood
- Benefit: Fixes potential deadlock/invalid context on RT systems

This commit is an excellent candidate for stable backporting. It fixes a
real bug (lockdep warning indicating invalid wait context), is small and
contained (10 lines), has been reviewed by domain experts, and follows a
well-established pattern. The change is a no-op on non-RT kernels and
fixes the bug on RT kernels.

**YES**

 drivers/gpio/gpio-sprd.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpio-sprd.c b/drivers/gpio/gpio-sprd.c
index 413bcd0a42405..2cc8abe705cdb 100644
--- a/drivers/gpio/gpio-sprd.c
+++ b/drivers/gpio/gpio-sprd.c
@@ -35,7 +35,7 @@
 struct sprd_gpio {
 	struct gpio_chip chip;
 	void __iomem *base;
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	int irq;
 };
 
@@ -54,7 +54,7 @@ static void sprd_gpio_update(struct gpio_chip *chip, unsigned int offset,
 	unsigned long flags;
 	u32 tmp;
 
-	spin_lock_irqsave(&sprd_gpio->lock, flags);
+	raw_spin_lock_irqsave(&sprd_gpio->lock, flags);
 	tmp = readl_relaxed(base + reg);
 
 	if (val)
@@ -63,7 +63,7 @@ static void sprd_gpio_update(struct gpio_chip *chip, unsigned int offset,
 		tmp &= ~BIT(SPRD_GPIO_BIT(offset));
 
 	writel_relaxed(tmp, base + reg);
-	spin_unlock_irqrestore(&sprd_gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&sprd_gpio->lock, flags);
 }
 
 static int sprd_gpio_read(struct gpio_chip *chip, unsigned int offset, u16 reg)
@@ -236,7 +236,7 @@ static int sprd_gpio_probe(struct platform_device *pdev)
 	if (IS_ERR(sprd_gpio->base))
 		return PTR_ERR(sprd_gpio->base);
 
-	spin_lock_init(&sprd_gpio->lock);
+	raw_spin_lock_init(&sprd_gpio->lock);
 
 	sprd_gpio->chip.label = dev_name(&pdev->dev);
 	sprd_gpio->chip.ngpio = SPRD_GPIO_NR;
-- 
2.51.0