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

[Marek Vasut <marex@xxxxxxx>]

On 4/22/22 11:20, Fabien DESSENNE wrote:
> Hi Marek,

Hi,

> I agree there is something wrong with the clock management in IRQ 
> context here and your patch goes in the right way.
> There are also some other problems regarding performance (enabling / 
> disabling clock each time we want to change the IO value, ...).

These are already fixed by separate patch:
[PATCH] irqchip/stm32: Do not call stm32_gpio_get() for edge triggered 
IRQs in EOI

> For these both issues I have a patch, which basically keeps the GPIO 
> clocks enabled from probe.
> I did not have time to submit it, but, considering your concerns, I will 
> do it in the coming days.
> For the time being I suggest that we do not apply your patch.

Is there anything specifically wrong with this patch ?

I think you should be easily able to apply your patch which keeps the 
clock enabled all the time on top of this one. The added bonus is that 
the commit message of this patch - which explains what the problem is 
with the LEVEL IRQs - would be retained, and so would bisectability in 
case your patch causes some sort of problem.

> BR
> Fabien
>
> On 21/04/2022 16:08, Marek Vasut 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@xxxxxxx>
> > Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>
> > Cc: Fabien Dessenne <fabien.dessenne@xxxxxxxxxxx>
> > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> > Cc: Marc Zyngier <maz@xxxxxxxxxx>
> > Cc: linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > To: linux-gpio@xxxxxxxxxxxxxxx
> > ---
> >   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);
> >   }