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

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Date:   Tue, 12 Feb 2019 13:20:16 +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>
Subject: Re: [PATCH v4 05/10] mfd: max77650: new core mfd driver

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.

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