linux-kernel - Re: [PATCH 2/2] gpio: gpio-grgpio: fix possible sleep-in-atomic-context bugs in grgpio_irq

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Date:   Wed, 8 Jan 2020 15:41:41 +0100
From:   Andreas Larsson <andreas@...sler.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] gpio: gpio-grgpio: fix possible
 sleep-in-atomic-context bugs in grgpio_irq_map/unmap()

On 2020-01-07 10:37, Linus Walleij wrote:
> However there is a deeper problem, this code was added by Andreas
> Larsson in 2013 and at the time this was a hacky way to deal with
> an interrupt that is actually hierarchical.
> 
> Since 2013 we have gained:
> - Hierarchical interrupt controllers
> - Hierarchical interrupt chip helpers in gpiolib
> 
> So this code really needs to be modernized using a hierarchical
> irqchip.
> 
> See for example commit:
> aa7d618ac65f ("gpio: ixp4xx: Convert to hierarchical GPIOLIB_IRQCHIP")
> for an example.
> 
> Who is using grgpio these days and could work on fixing this up?

I will put on my list to look into this. GRGPIO is used in all our 
chips, and in most designs made by our customers.

The main hurdle with the interrupt handling in the current driver was to 
both allow several lines to generate the same system interrupt and at 
the same time make sure to not register any system interrupts for any 
lines until the user actually requests it (as in the general case all 
interrupts would be registered leading to clashes with interrupts that 
cannot necessarily be shared). Hopefully, the hierarchical interrupt 
controller and chip helper functionalities can cater for these requirements.

Best regards,
Andreas Larsson