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

From: Linus Walleij <linus.walleij@linaro.org>
To: Marek Vasut <marex@denx.de>
Cc: linux-gpio@vger.kernel.org,
	 Alexandre Torgue <alexandre.torgue@foss.st.com>,
	 Fabien Dessenne <fabien.dessenne@foss.st.com>,
	Marc Zyngier <maz@kernel.org>,
	 linux-stm32@st-md-mailman.stormreply.com,
	 linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] irqchip/stm32: Keep pinctrl block clock enabled when LEVEL IRQ requested
Date: Sat, 23 Apr 2022 00:11:10 +0200	[thread overview]
Message-ID: <CACRpkdboaSzhduydSzqK+m1WyXz8ZWF43Ey0bxHKWujROSuDew@mail.gmail.com> (raw)
In-Reply-To: <20220421140827.214088-1-marex@denx.de>

On Thu, Apr 21, 2022 at 4:08 PM Marek Vasut <marex@denx.de> wrote:

> 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

Patch applied to fixes, tweaked subject to pinctrl: stm32:

Yours,
Linus Walleij

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