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

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Date:	Mon, 13 Jul 2015 16:12:17 +0300
From:	Roger Quadros <rogerq@...com>
To:	nick <xerofoify@...il.com>, Tony Lindgren <tony@...mide.com>
CC:	<devicetree@...r.kernel.org>, <computersforpeace@...il.com>,
	<linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
	<ezequiel@...guardiasur.com.ar>, <bcousson@...libre.com>,
	<linux-omap@...r.kernel.org>, <dwmw2@...radead.org>
Subject: Re: [PATCH 03/12] mtd: nand: omap: Move IRQ handling from GPMC to
 NAND driver

On 13/07/15 16:03, nick wrote:
> 
> 
> On 2015-07-13 09:01 AM, Tony Lindgren wrote:
>> * nick <xerofoify@...il.com> [150713 05:54]:
>>> On 2015-07-13 08:40 AM, Tony Lindgren wrote:
>>>> * Roger Quadros <rogerq@...com> [150713 03:07]:
>>>>  
>>>>> 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,
>>>
>>> Is that a good idea as to my knowledge of OMAP platforms that register is hardware
>>> dependent and therefore that may be an issue unless your idea is to create device
>>> tables like the way they do in the nand subsystems to support various vendor's 
>>> nand flash expect here for the pins on OMAP SOCs.
>>
>> Do you mean mapping irqs based on the GPMC_IRQSTATUS register
>> bits? If so, that's pretty much how all the GPIO drivers
>> handle them. We can have a SoC specific irqmask of the valid
>> bits passed from the dts files, and if necessary we can also
>> add custom SoC specific IRQ handlers to the GPMC driver if
>> needed.
>>
>> The idea is that the NAND driver can just request the irq
>> from the GPMC driver and do whatever it wants with the
>> interrupt.
>>
>> Regards,
>>
>> Tony
>>
> Tony,
> That is what I was hoping the code was doing. So what appears to be the problem with the 
> patches related to irq requesting from the GPMC driver.
> Cheers,
> Nick 
> 

The problem with this patch is that it expects GPMC_IRQ registers
to be accessible by the NAND driver and looses the 2 to 4 pins
of WAIT pin edge detection interrupt capability if it is needed
for generic use. (not NAND/GPMC memory specific)

cheers,
-roger
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