linux-kernel - Re: [PATCH v4 05/10] mfd: max77650: new core mfd driver

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Date:   Wed, 13 Feb 2019 09:25:53 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Pavel Machek <pavel@....cz>,
        Sebastian Reichel <sre@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Input <linux-input@...r.kernel.org>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>, broonie@...nel.org
Subject: Re: [PATCH v4 05/10] mfd: max77650: new core mfd driver

On Tue, 12 Feb 2019, Lee Jones wrote:

> On Tue, 12 Feb 2019, Bartosz Golaszewski wrote:
> 
> > wt., 12 lut 2019 o 12:14 Lee Jones <lee.jones@...aro.org> napisał(a):
> > >
> > > On Tue, 12 Feb 2019, Bartosz Golaszewski wrote:
> > >
> > > > wt., 12 lut 2019 o 11:18 Lee Jones <lee.jones@...aro.org> napisał(a):
> > > > >
> > > > > On Tue, 12 Feb 2019, Bartosz Golaszewski wrote:
> > > > >
> > > > > > wt., 12 lut 2019 o 10:55 Lee Jones <lee.jones@...aro.org> napisał(a):
> > > > > > >
> > > > > > >  * The declaration of a superfluous struct
> > > > > > >  * 100 lines of additional/avoidable code
> > > > > > >  * Hacky hoop jumping trying to fudge VIRQs into resources
> > > > > > >  * Resources were designed for HWIRQs (unless a domain is present)
> > > > > > >  * Loads of additional/avoidable CPU cycles setting all this up
> > > > > >
> > > > > > While the above may be right, this one is negligible and you know it. :)
> > > > >
> > > > > You have nested for() loops.  You *are* wasting lots of cycles.
> > > > >
> > > > > > > Need I go on? :)
> > > > > > >
> > > > > > > Surely the fact that you are using both sides of an API
> > > > > > > (devm_regmap_init_i2c and regmap_irq_get_*) in the same driver, must
> > > > > > > set some alarm bells ringing?
> > > > > > >
> > > > > > > This whole HWIRQ setting, VIRQ getting, resource hacking is a mess.
> > > > > > >
> > > > > > > And for what?  To avoid passing IRQ data to a child driver?
> > > > > >
> > > > > > What do you propose? Should I go back to the approach in v1 and pass
> > > > > > the regmap_irq_chip_data to child drivers?
> > > > >
> > > > > I'm saying you should remove all of this hackery and pass IRQs as they
> > > > > are supposed to be passed (like everyone else does).
> > > >
> > > > I'm not sure what you mean by "like everyone else does" - different
> > > > mfd drivers seem to be doing different things. Is a simple struct
> > > > containing virtual irq numbers passed to sub-drivers fine?
> > >
> > > How do you plan on deriving the VIRQs to place into the struct?
> > 
> > Exampe:
> > 
> > struct max77650_gpio_pdata {
> >     int gpi_irq;
> > };
> > 
> > In MFD driver:
> > 
> > struct max77650_gpio_pdata *gpio_data = devm_kmalloc(dev, sizeof(*gpio_data));
> > 
> > gpio_data->gpi_irq = regmap_irq_get_virq(irqchip_data, GPI_NUM);
> > 
> > gpio_cell.platform_data = gpio_data;
> > 
> > In GPIO driver:
> > 
> > struct max77650_gpio_pdata *gpio_data = pdev->dev.platform_data;
> > 
> > int irq = gpio_data->gpi_irq;
> 
> Definitely not.  What you're trying to do is a hack.
> 
> If you're using Regmap to handle your IRQs, then you should use Regmap
> in the client to pull them out.  Setting them via Regmap, then pulling
> them out again in the *same driver*, only to store them in platform
> data to be passed to a child device is bonkers.
> 
> *Either* use the MFD provided platform-data helpers *or* pass and
> handle them via the Regmap APIs, *not* both.

Right, a plan has been formed.

Hopefully this works and you can avoid all this dancing around.

Firstly, you need to make a small change to:

  drivers/base/regmap/regmap-irq.c

Add the following function:

  struct irq_domain *regmap_irq_get_domain(struct regmap *map)

As you can see, it will return the IRQ Domain for the chip.

You can then pass this IRQ domain to mfd_add_devices() and it will do
the HWIRQ => VIRQ mapping for you on the fly.  Meaning that you can
remove all the nastiness in max77650_setup_irqs() and have the Input
device use the standard (e.g. platform_get_irq()) APIs.

How does that Sound?

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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