linux-kernel - Re: [PATCH v2 2/2] irqchip: Add Qualcomm MPM controller driver

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Message-ID: <20211130091708.GH10105@dragon>
Date:   Tue, 30 Nov 2021 17:17:08 +0800
From:   Shawn Guo <shawn.guo@...aro.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Maulik Shah <quic_mkshah@...cinc.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] irqchip: Add Qualcomm MPM controller driver

On Tue, Nov 30, 2021 at 08:42:53AM +0000, Marc Zyngier wrote:
> On Tue, 30 Nov 2021 02:31:52 +0000,
> Shawn Guo <shawn.guo@...aro.org> wrote:
> > 
> > + Maulik
> > 
> > On Mon, Nov 29, 2021 at 03:24:39PM +0000, Marc Zyngier wrote:
> > [...]
> > > > > > @@ -430,6 +430,14 @@ config QCOM_PDC
> > > > > >  	  Power Domain Controller driver to manage and configure wakeup
> > > > > >  	  IRQs for Qualcomm Technologies Inc (QTI) mobile chips.
> > > > > >  
> > > > > > +config QCOM_MPM
> > > > > > +	bool "QCOM MPM"
> > > > > 
> > > > > Can't be built as a module?
> > > > 
> > > > The driver is implemented as a builtin_platform_driver().
> > > 
> > > This, on its own, shouldn't preclude the driver from being built as a
> > > module. However, the config option only allows it to be built in. Why?
> > 
> > I just tried to build it as a module, and it seems that "irq_to_desc" is
> > only available for built-in build.
> 
> Yet another thing that you should not be using. The irqdomain code
> gives you everything you need without having to resort to the
> internals of the core IRQ infrastructure.

I see.  I should use irq_get_irq_data() rather than &desc->irq_data.

> 
> > > Furthermore, why would you look up anywhere other than the wake-up
> > > domain? My impression was that only these interrupts would require
> > > being re-triggered.
> > 
> > Both domains have MPM pins that could wake up system.
> 
> Then why do you need two domains?

This is basically the same situation as qcom-pdc, and I have some
description about that in the commit log:

- For given SoC, a fixed number of MPM pins are supported, e.g. 96 pins
  on QCM2290.  Each of these MPM pins can be either a MPM_GIC pin or
  a MPM_GPIO pin. The mapping between MPM_GIC pin and GIC interrupt
  is defined by SoC, as well as the mapping between MPM_GPIO pin and
  GPIO number.  The former mapping can be found as the SoC data in this
  MPM driver, while the latter can be found as the msm_gpio_wakeirq_map[]
  in TLMM driver.

- Two irq domains are created for a single irq_chip to handle MPM_GIC
  and MPM_GPIO pins respectively, i.e. MPM_GIC domain and MPM_GPIO domain.
  The former is a child domain of GIC irq domain, while the latter is
  a parent domain of TLMM/GPIO irq domain.

Shawn