linux-kernel - Re: [PATCH 03/12] mtd: nand: omap: Move IRQ handling from GPMC to NAND driver

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Message-ID: <20150713124059.GF26485@atomide.com>
Date:	Mon, 13 Jul 2015 05:40:59 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Roger Quadros <rogerq@...com>
Cc:	dwmw2@...radead.org, computersforpeace@...il.com,
	bcousson@...libre.com, ezequiel@...guardiasur.com.ar,
	linux-mtd@...ts.infradead.org, linux-omap@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/12] mtd: nand: omap: Move IRQ handling from GPMC to
 NAND driver

* Roger Quadros <rogerq@...com> [150713 03:07]:
> Tony,
> 
> On 13/07/15 10:10, Tony Lindgren wrote:
> > * Roger Quadros <rogerq@...com> [150710 05:26]:
> >> Since the Interrupt Events are used only by the NAND driver,
> >> there is no point in managing the Interrupt registers
> >> in the GPMC driver and complicating it with irqchip modeling.
> > 
> > I don't think it's a good idea to allow external drivers to
> > tinker directly with GPMC registers. How about just set up GPMC
> > as an irqchip for the edge detection interrupts?
> > 
> > I think we already have devices with multiple NAND chips. And
> > there's nothing stopping other drivers from using the edge
> > detection interrupts.
> 
> OK. The GPMC_IRQ registers manage 2 NAND specific interrupts
> (terminalcount and fifo) and 'n' WAIT pin edge interrupts.
> 
>  So we can model this as a irqchip with 'n + 2' interrupts.

OK
 
> We need to take care that if a GPMC chip select needs a
> wait pin then it can't be used as a generic interrupt.
> 
> We need to get rid of omap_dev_ready() in nand/omap2.c as
> it accesses the GPMC_STATUS register directly. Plus it is
> hard coded to only monitor wait0 pin.

OK
 
> What is the best map we should use for irqchip?
> Some Socs have 4 WAIT pins, some have 3 and some have 2.
> 
> Should we start with 0,1,2, for the wait pins and use the next
> available free one for the NAND?

Maybe we can just use the bits defined for each SoC in the
GPMC_IRQSTATUS register for the mapping?  
Regards,

Tony
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