linux-kernel - Re: Add hierarchical irq_domain for i2c based gpio expander pca9505

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Date:   Thu, 12 Oct 2017 10:40:11 +0530
From:   Abhishek Shah <abhishek.shah@...adcom.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Takahiro Akashi <takahiro.akashi@...aro.org>
Cc:     linux-gpio@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        Sandeep Tripathy <sandeep.tripathy@...adcom.com>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>
Subject: Re: Add hierarchical irq_domain for i2c based gpio expander pca9505

+BCM kernel feedback.
Sorry for duplicated mails, had HTML formatting issue.

On Wed, Oct 11, 2017 at 5:50 PM, Abhishek Shah
<abhishek.shah@...adcom.com> wrote:
> Hi Linus,
>
> I am facing one issue, where; while disabling/ masking interrupts just
> before kexec reboot, access to gpio expander pca9505 residing over
> i2c bus hangs, because i2c interrupts are disabled prior to writing
> pca9505 register.
>
> In our chip, we have 3 irq_domain, namely gicv3, bcm-iproc-gpio [GPIO
> controller with ~150 pins] and pca953x [40-pin IO expander pca9505].
>
> bcm-iproc-gpio and i2c interrupts among the other interrupts  are
> registered to gicv3 and
> pca953x interrupts are registered to bcm-iproc-gpio.
>
> So, interrupt from pca953x gets routed like...
> pca953x-> bcm-iproc-gpio-> gicv3
>
> Now, I see that, got GPIO controllers, an independent IRQ domain is
> added using gpiochip_irqchip_add_nested
> or gpiochip_irqchip_add, which makes use of irq_domain_add_simple like this:
> gpiochip->irqdomain = irq_domain_add_simple(of_node,
>                                         gpiochip->ngpio, first_irq,
>                                         &gpiochip_domain_ops, gpiochip);
>
> Is it possible to add hierarchical irq_domain for pca953x to be child
> of bcm-iproc-gpio and bcm-iproc-gpio irq_domain  to be child of gicv3
> using irq_domain_add_hierarchy instead of current  irq_domain_add_simple API??
>
> Would that make sure that first all interrupts of child irq_domain
> gets disabled?
>
>
> Now, this is where I am facing issue during kexec_reboot:
>
> static void machine_kexec_mask_interrupts(void)                  /*
> function is present in arch/arm64/kernel/machine_kexec.c file */
> {
>         unsigned int i;
>         struct irq_desc *desc;
>
>         for_each_irq_desc(i, desc) {
>                 struct irq_chip *chip;
>                 int ret;
>
>                 chip = irq_desc_get_chip(desc);
>                 if (!chip)
>                         continue;
>
>                 /*
>                  * First try to remove the active state. If this
>                  * fails, try to EOI the interrupt.
>                  */
>                 ret = irq_set_irqchip_state(i, IRQCHIP_STATE_ACTIVE,
> false);   /* access to PCA9505 register hangs here and kexec reboot
> fails! */
>
>                 if (ret && irqd_irq_inprogress(&desc->irq_data) &&
>                     chip->irq_eoi)
>                         chip->irq_eoi(&desc->irq_data);
>
>                 if (chip->irq_mask)
>                         chip->irq_mask(&desc->irq_data);
>
>                 if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
>                         chip->irq_disable(&desc->irq_data);
>         }
> }
>
> In my case, when this loop runs, initially it masks all GICv3
> interrupts,i.e. i2c interrupts are also disabled.
> Now when irq_set_irqchip_state gets executed in process of masking
> pca9505 interrupts, .irq_bus_sync_unlock
> callback (pca953x_irq_bus_sync_unlock) hangs because i2c interrupts are masked.
>
> Do you think adding "irq_domain_add_hierarchy" for GPIO controllers
> can solve this problem?
> or do you suggest change in the way "machine_kexec_mask_interrupts" is
> implemented?
>
>
> Regards,
> Abhishek