linux-kernel - RE: [PATCH v5 08/10] irqchip: Add Sunplus SP7021 interrupt controller driver

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Message-ID: <8fa00c3b55874e90b5baae1f84010997@cqplus1.com>
Date:   Wed, 8 Dec 2021 09:28:42 +0000
From:   qinjian[覃健] <qinjian@...lus1.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        Wells Lu 呂芳騰 <wells.lu@...plus.com>
Subject: RE: [PATCH v5 08/10] irqchip: Add Sunplus SP7021 interrupt controller
 driver

> -----Original Message-----
> From: Marc Zyngier <maz@...nel.org>
> Sent: Wednesday, December 8, 2021 3:45 PM
> To: qinjian[覃健] <qinjian@...lus1.com>
> Cc: robh+dt@...nel.org; mturquette@...libre.com; sboyd@...nel.org; tglx@...utronix.de; p.zabel@...gutronix.de;
> linux@...linux.org.uk; broonie@...nel.org; arnd@...db.de; linux-arm-kernel@...ts.infradead.org; devicetree@...r.kernel.org; linux-
> kernel@...r.kernel.org; linux-clk@...r.kernel.org; Wells Lu 呂芳騰 <wells.lu@...plus.com>
> Subject: Re: [PATCH v5 08/10] irqchip: Add Sunplus SP7021 interrupt controller driver
> 
> On 2021-12-08 07:15, qinjian[覃健] wrote:
> >> > +void sp_intc_set_ext(u32 hwirq, int ext_num)
> >> > +{
> >> > +	sp_intc_assign_bit(hwirq, REG_INTR_PRIORITY, !ext_num);
> >> > +}
> >> > +EXPORT_SYMBOL_GPL(sp_intc_set_ext);
> >>
> >> No way. We don't export random symbols without a good justification,
> >> and you didn't give any.
> >>
> >
> > This function called by SP7021 display driver to decide DISPLAY_IRQ
> > routing to which parent irq (EXT_INT0 or EXT_INT1).
> 
> Based on what? How can a display driver decide which parent is
> appropriate? What improvement does this bring?

In default, all IRQ routing to EXT_INT0, which processed by CPU0
Some device's IRQ need low latency, like display, so routing DISPLAY_IRQ to EXT_INT1,
which processed by CPU1 (set /proc/irq/<EXT_INT1>/smp_affinity_list)