linux-kernel - Re: [RFT PATCH v2] gpiolib: allow gpio irqchip to map irqs dynamically

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Message-ID: <20170928083348.GI4630@lahna.fi.intel.com>
Date:   Thu, 28 Sep 2017 11:33:48 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jerome Brunet <jbrunet@...libre.com>, chrisjohgorman@...il.com
Subject: Re: [RFT PATCH v2] gpiolib: allow gpio irqchip to map irqs
 dynamically

On Fri, Jul 21, 2017 at 11:49:00AM -0500, Grygorii Strashko wrote:
> Now IRQ mappings are always created for all (allowed) GPIOs in gpiochip in
> gpiochip_irqchip_add_key() which goes against the idea of SPARSE_IRQ and,
> as result, leads to:
>  - increasing of memory consumption for IRQ descriptors most of which will
> never ever be used (espessially on platform with a high number of GPIOs).
> (sizeof(struct irq_desc) == 256 on my tested platforms)
>  - imposibility to use GPIO irqchip APIs by gpio drivers when HW implements
> GPIO IRQ functionality as IRQ crossbar/router which has only limited
> number of IRQ outputs (example from [1], all GPIOs can be mapped on only 8
> IRQs).
> 
> Hence, remove static IRQ mapping code from gpiochip_irqchip_add_key() and
> instead replace irq_find_mapping() with irq_create_mapping() in
> gpiochip_to_irq(). Also add additional gpiochip_irqchip_irq_valid() calls
> in gpiochip_to_irq() and gpiochip_irq_map().
> 
> After this change gpio2irq mapping will happen the following way when GPIO
> irqchip APIs are used by gpio driver:
>  - IRQ mappings will be created statically if driver passes first_irq>0
> vlaue in gpiochip_irqchip_add_key().
>  - IRQ mappings will be created dynamically from gpio_to_irq() or
> of_irq_get().
> 
> Tested on am335x-evm and dra72-evm-revc.
> - dra72-evm-revc: number of created irq mappings decreased from 402 -> 135
>   Mem savings 267*256 = 68352 (66kB)
> - am335x-evm: number of created irq mappings decreased from 188 -> 63
>   Mem savings 125*256 = 32000 (31kB)
> 
> [1] https://lkml.org/lkml/2017/6/15/428
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>

Hi Grygorii,

It looks like dc749a09ea5e41 ("gpiolib: allow gpio irqchip to map irqs
dynamically") broke the quirk we added for some Intel Cherryview
systems [1]. Basically after this keyboard of those systems stopped
working again.

Any idea what might be wrong?

I've CC'd Chris Gorman who reported the issue.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=194945