linux-kernel - Questions about interrupt

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Message-Id: <89DE4FD5-D0D7-469E-A20A-69AEDEB127BA@oracle.com>
Date:	Sun, 14 Jun 2015 00:49:54 +0800
From:	Alex Feng <li.feng@...cle.com>
To:	linux-kernel@...r.kernel.org
Cc:	fengguang.wu@...el.com
Subject: Questions about interrupt

Hi experts,

I have trouble about interrupt. I need low level trigger the interrupt. My control flow is that when data is less than a threshold, it needs keeping interrupt until data is supplied.  

So I use the flag `IRQ_TYPE_LEVEL_LOW `, but it doesn’t work. I have also tried `IRQF_TRIGGER_LOW`, it also doesn’t work.

I have checked the hardware register, the interrupt GPIO is still `falling edges`, not `low level`.

My board is ARM S3C6410 tiny board. 

   221	/* inkprinter */
   222	#define S3C64XX_PA_INKPRINTER (0x30000000)
   223	#define S3C64XX_SZ_INKPRINTER SZ_1M
   224	static struct resource inkprinter_resources[] = {
   225		[0] = {
   226			.start		= S3C64XX_PA_INKPRINTER,
   227			.end		= S3C64XX_PA_INKPRINTER + S3C64XX_SZ_INKPRINTER,
   228			.flags		= IORESOURCE_MEM,
   229		},
   230		[1] = {
   231			.start		= IRQ_EINT(1),
   232			.end		= IRQ_EINT(1),
   233			.flags = IORESOURCE_IRQ | IRQ_TYPE_LEVEL_LOW,
   234		}
   235	};
   236	static struct platform_device s3c_device_inkprinter = {
   237		.name			= "inkprinter",
   238		.num_resources	= ARRAY_SIZE(inkprinter_resources),
   239		.resource		= inkprinter_resources,
   240	};
   241

My question is :

Is `IRQ_TYPE_LEVEL_LOW ` or `IRQF_TRIGGER_LOW `  for low level trigger? Or some other problem? Any tips?
Your response will be highly appreciated. 

Thanks,
/Alex--
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