linux-kernel - Re: [PATCH] irqchip: Renesas IRQC driver

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Date:	Thu, 12 Dec 2013 02:36:28 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Magnus Damm <magnus.damm@...il.com>, linux-kernel@...r.kernel.org
CC:	linux-sh@...r.kernel.org, benh@...nel.crashing.org,
	grant.likely@...retlab.ca, horms@...ge.net.au, tglx@...utronix.de
Subject: Re: [PATCH] irqchip: Renesas IRQC driver

Hello.

On 02/27/2013 11:15 AM, Magnus Damm wrote:

> From: Magnus Damm <damm@...nsource.se>

    Magnus, explain me one thing about your driver please.

> This patch adds a driver for external IRQ pins connected
> to the IRQC hardware block on recent SoCs from Renesas.
>
> The IRQC hardware block is used together with more
> recent ARM based SoCs using the GIC. As usual the GIC
> requires external IRQ trigger setup somewhere else
> which in this particular case happens to be IRQC.
>
> This driver implements the glue code needed to configure
> IRQ trigger and also handle mask/unmask and demux of
> external IRQ pins hooked up from the IRQC to the GIC.

    Judging on the R8A779x manual pictures, IRQn enter the SoC via IRQC, right?
Why then you call request_irq() on GIC interrupt numbers and expect an 
interrupt to "enter" from the GIC side, and then only read IRQC's 
DETECT_STATUS register to make sure the matching IRQn is really active (you 
call it demux, but I don't really see much of a demultiplexing there). This 
seems to me fundamentally broken, and is probably why the interrupt from PHY 
doesn't happen despite I set the interrupt type to active low via a call to 
irq_set_irq_type()...

> Tested on r8a73a4 but is designed to work with a wide
> range of SoCs. The driver requires one GIC SPI per
> external IRQ pin to operate.  Each driver instance
> will handle up to 32 external IRQ pins.

    Ah, so you've even tested it... I got an impression from your words that 
the driver hasn't been tested.

> The SoCs using this driver are currently mainly used
> together with regular platform devices so this driver
> allows configuration via platform data to support things
> like static interrupt base address. DT support will
> be added incrementally in the not so distant future.

> Signed-off-by: Magnus Damm <damm@...nsource.se>

WBR, Sergei

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