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

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Date:   Thu, 28 Sep 2017 17:26:34 +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 Thu, Sep 28, 2017 at 09:02:12AM -0500, Grygorii Strashko wrote:
> 
> 
> On 09/28/2017 03:33 AM, Mika Westerberg wrote:
> > 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?
> 
> Yes. kernel do not map all GPIO IRQs by default now.
> I've red related discussion and, as per my understanding (correct me if i'm wrong),
> on this platform all GPIO IRQs have to be mapped on fixed range of Linux IRQs.
> In this case, It's reasonable to specify first_irq parameter in gpiochip_irqchip_add()
> which should force IRQ mapping creation.

So can you propose what value I should pass then? It was working just
fine until this change.