linux-kernel - Re: [PATCH v7 2/2] irqchip: Add Qualcomm MPM controller driver

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Date:   Fri, 04 Mar 2022 07:59:15 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Shawn Guo <shawn.guo@...aro.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Maulik Shah <quic_mkshah@...cinc.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/2] irqchip: Add Qualcomm MPM controller driver

On Thu, 03 Mar 2022 04:02:29 +0000,
Shawn Guo <shawn.guo@...aro.org> wrote:
> 
> On Wed, Mar 02, 2022 at 01:57:27PM +0000, Marc Zyngier wrote:
> > This code actually makes me ask more questions. Why is it programming
> > 2 'pins' for each IRQ?
> 
> The mapping between MPM pin and GIC IRQ is not strictly 1-1.  There are
> some rare case that up to 2 MPM pins map to a single GIC IRQ, for
> example the last two in QC2290 'qcom,mpm-pin-map' below.
> 
> 	qcom,mpm-pin-map = <2 275>,     /* tsens0_tsens_upper_lower_int */
> 			   <5 296>,     /* lpass_irq_out_sdc */
> 			   <12 422>,    /* b3_lfps_rxterm_irq */
> 			   <24 79>,     /* bi_px_lpi_1_aoss_mx */
> 			   <86 183>,    /* mpm_wake,spmi_m */
> 			   <90 260>,    /* eud_p0_dpse_int_mx */
> 			   <91 260>;    /* eud_p0_dmse_int_mx */
> 
> 
> The downstream uses a DT bindings that specifies GIC hwirq number in
> client device nodes.  In that case, d->hwirq in the driver is GIC IRQ
> number, and the driver will need to query mapping table, find out the
> possible 2 MPM pins, and set them up.
> 
> The patches I'm posting here use a different bindings that specifies MPM
> pin instead in client device nodes.  Thus the driver can simply get the
> MPM pin from d->hwirq, so that the whole look-up procedure can be saved.

It still remains that there is no 1:1 mapping between input and
output, which is the rule #1 to be able to use a hierarchical setup.

/me puzzled.

>
> > 
> > > 
> > > It seems MPM_REG_POLARITY is only meant for level interrupts, since edge
> > > interrupts already have separate registers for rising and falling.
> > 
> > Then level interrupts must clear both the edge registers at all times.
> 
> The downstream logic already covers that, right?  The edge register bits
> will be cleared as long as 'flowtype' is not EDGE.

I am talking about *your* code, not the Qualcomm stuff.

	M.

-- 
Without deviation from the norm, progress is not possible.