[PATCH] irqchip/stm32: Keep pinctrl block clock enabled when LEVEL IRQ requested

[Marek Vasut <marex@denx.de>]

The current EOI handler for LEVEL triggered interrupts calls clk_enable(),
register IO, clk_disable(). The clock manipulation requires locking which
happens with IRQs disabled in clk_enable_lock(). Instead of turning the
clock on and off all the time, enable the clock in case LEVEL interrupt is
requested and keep the clock enabled until all LEVEL interrupts are freed.
The LEVEL interrupts are an exception on this platform and seldom used, so
this does not affect the common case.

This simplifies the LEVEL interrupt handling considerably and also fixes
the following splat found when using preempt-rt:
 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 0 at kernel/locking/rtmutex.c:2040 __rt_mutex_trylock+0x37/0x62
 Modules linked in:
 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.10.109-rt65-stable-standard-00068-g6a5afc4b1217 #85
 Hardware name: STM32 (Device Tree Support)
 [<c010a45d>] (unwind_backtrace) from [<c010766f>] (show_stack+0xb/0xc)
 [<c010766f>] (show_stack) from [<c06353ab>] (dump_stack+0x6f/0x84)
 [<c06353ab>] (dump_stack) from [<c01145e3>] (__warn+0x7f/0xa4)
 [<c01145e3>] (__warn) from [<c063386f>] (warn_slowpath_fmt+0x3b/0x74)
 [<c063386f>] (warn_slowpath_fmt) from [<c063b43d>] (__rt_mutex_trylock+0x37/0x62)
 [<c063b43d>] (__rt_mutex_trylock) from [<c063c053>] (rt_spin_trylock+0x7/0x16)
 [<c063c053>] (rt_spin_trylock) from [<c036a2f3>] (clk_enable_lock+0xb/0x80)
 [<c036a2f3>] (clk_enable_lock) from [<c036ba69>] (clk_core_enable_lock+0x9/0x18)
 [<c036ba69>] (clk_core_enable_lock) from [<c034e9f3>] (stm32_gpio_get+0x11/0x24)
 [<c034e9f3>] (stm32_gpio_get) from [<c034ef43>] (stm32_gpio_irq_trigger+0x1f/0x48)
 [<c034ef43>] (stm32_gpio_irq_trigger) from [<c014aa53>] (handle_fasteoi_irq+0x71/0xa8)
 [<c014aa53>] (handle_fasteoi_irq) from [<c0147111>] (generic_handle_irq+0x19/0x22)
 [<c0147111>] (generic_handle_irq) from [<c014752d>] (__handle_domain_irq+0x55/0x64)
 [<c014752d>] (__handle_domain_irq) from [<c0346f13>] (gic_handle_irq+0x53/0x64)
 [<c0346f13>] (gic_handle_irq) from [<c0100ba5>] (__irq_svc+0x65/0xc0)
 Exception stack(0xc0e01f18 to 0xc0e01f60)
 1f00:                                                       0000300c 00000000
 1f20: 0000300c c010ff01 00000000 00000000 c0e00000 c0e07714 00000001 c0e01f78
 1f40: c0e07758 00000000 ef7cd0ff c0e01f68 c010554b c0105542 40000033 ffffffff
 [<c0100ba5>] (__irq_svc) from [<c0105542>] (arch_cpu_idle+0xc/0x1e)
 [<c0105542>] (arch_cpu_idle) from [<c063be95>] (default_idle_call+0x21/0x3c)
 [<c063be95>] (default_idle_call) from [<c01324f7>] (do_idle+0xe3/0x1e4)
 [<c01324f7>] (do_idle) from [<c01327b3>] (cpu_startup_entry+0x13/0x14)
 [<c01327b3>] (cpu_startup_entry) from [<c0a00c13>] (start_kernel+0x397/0x3d4)
 [<c0a00c13>] (start_kernel) from [<00000000>] (0x0)
 ---[ end trace 0000000000000002 ]---

Power consumption measured on STM32MP157C DHCOM SoM is not increased or
is below noise threshold.

Fixes: 47beed513a85b ("pinctrl: stm32: Add level interrupt support to gpio irq chip")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Fabien Dessenne <fabien.dessenne@foss.st.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: linux-stm32@st-md-mailman.stormreply.com
Cc: linux-arm-kernel@lists.infradead.org
To: linux-gpio@vger.kernel.org
---
 drivers/pinctrl/stm32/pinctrl-stm32.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/pinctrl/stm32/pinctrl-stm32.c b/drivers/pinctrl/stm32/pinctrl-stm32.c
index 242d1c37c6e4..7aecd0efde07 100644
--- a/drivers/pinctrl/stm32/pinctrl-stm32.c
+++ b/drivers/pinctrl/stm32/pinctrl-stm32.c
@@ -226,6 +226,13 @@ static void stm32_gpio_free(struct gpio_chip *chip, unsigned offset)
 	pinctrl_gpio_free(chip->base + offset);
 }
 
+static int stm32_gpio_get_noclk(struct gpio_chip *chip, unsigned int offset)
+{
+	struct stm32_gpio_bank *bank = gpiochip_get_data(chip);
+
+	return !!(readl_relaxed(bank->base + STM32_GPIO_IDR) & BIT(offset));
+}
+
 static int stm32_gpio_get(struct gpio_chip *chip, unsigned offset)
 {
 	struct stm32_gpio_bank *bank = gpiochip_get_data(chip);
@@ -233,7 +240,7 @@ static int stm32_gpio_get(struct gpio_chip *chip, unsigned offset)
 
 	clk_enable(bank->clk);
 
-	ret = !!(readl_relaxed(bank->base + STM32_GPIO_IDR) & BIT(offset));
+	ret = stm32_gpio_get_noclk(chip, offset);
 
 	clk_disable(bank->clk);
 
@@ -317,7 +324,7 @@ static void stm32_gpio_irq_trigger(struct irq_data *d)
 		return;
 
 	/* If level interrupt type then retrig */
-	level = stm32_gpio_get(&bank->gpio_chip, d->hwirq);
+	level = stm32_gpio_get_noclk(&bank->gpio_chip, d->hwirq);
 	if ((level == 0 && bank->irq_type[d->hwirq] == IRQ_TYPE_LEVEL_LOW) ||
 	    (level == 1 && bank->irq_type[d->hwirq] == IRQ_TYPE_LEVEL_HIGH))
 		irq_chip_retrigger_hierarchy(d);
@@ -359,6 +366,7 @@ static int stm32_gpio_irq_request_resources(struct irq_data *irq_data)
 {
 	struct stm32_gpio_bank *bank = irq_data->domain->host_data;
 	struct stm32_pinctrl *pctl = dev_get_drvdata(bank->gpio_chip.parent);
+	unsigned long flags;
 	int ret;
 
 	ret = stm32_gpio_direction_input(&bank->gpio_chip, irq_data->hwirq);
@@ -372,6 +380,10 @@ static int stm32_gpio_irq_request_resources(struct irq_data *irq_data)
 		return ret;
 	}
 
+	flags = irqd_get_trigger_type(irq_data);
+	if (flags & IRQ_TYPE_LEVEL_MASK)
+		clk_enable(bank->clk);
+
 	return 0;
 }
 
@@ -379,6 +391,9 @@ static void stm32_gpio_irq_release_resources(struct irq_data *irq_data)
 {
 	struct stm32_gpio_bank *bank = irq_data->domain->host_data;
 
+	if (bank->irq_type[irq_data->hwirq] & IRQ_TYPE_LEVEL_MASK)
+		clk_disable(bank->clk);
+
 	gpiochip_unlock_as_irq(&bank->gpio_chip, irq_data->hwirq);
 }
 
-- 
2.35.1