linux-kernel - Re: Does it need to implement irq_set_type method in the ioapic

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Date:	Tue, 18 Feb 2014 18:34:38 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	carl peng <carlpeng008@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	mingo@...hat.com, x86@...nel.org, pingfank@...ux.vnet.ibm.com,
	yoshihiro.yunomae.ez@...achi.com, linux-kernel@...r.kernel.org
Subject: Re: Does it need to implement irq_set_type method in the ioapic_chip?

This is an ACPI device connecting to an internal IOAPIC? If not, how is it connected?

On February 18, 2014 6:32:44 PM PST, carl peng <carlpeng008@...il.com> wrote:
>Hi Thomas,
>
>Thanks a lot for your help!
>
>But I still have some confusion. Could you please help to give some
>suggestions to me?
>
>1) This device is a ACPI device, the hardware engineer designed it as
>falling edge interrupt trigger
>mode, does it need to re-work the hardware and modify it as rising
>edge trigger mode to suit the
>Linux APIC driver architecture?
>2) Why does APIC driver not implement the irq_set_type method?  if
>implement it, will supply more
>free space for the device driver developer(they can set the interrupt
>trigger mode by calling request_irq).
>
>Thank you!
>Carl
>
>
>On Wed, Feb 19, 2014 at 4:13 AM, Thomas Gleixner <tglx@...utronix.de>
>wrote:
>> On Tue, 18 Feb 2014, carl peng wrote:
>>
>> Carl, sending the same mail twice within an hour does not speed up
>> things. It's quite likely that it gets ignored.
>>
>>> 1. Does it need to implement irq_set_type method in the ioapic_chip
>>> structure?
>>
>> No. The irq type is configured by the type of the interrupt or the
>> BIOS.
>>
>> ISA  interrupts are always polarity zero edge triggered (historic)
>>
>> PCI  interrupts are always polarity one level triggered
>>
>> PCIE interrupts are either legacy PCI or with MSI[X] always edge
>>      triggered
>>
>>> 2. if no need to implement it, how can device driver set the trigger
>mode
>>> of APIC interrupt controller pin?
>>
>> Not at all.
>>
>> The device which is connected to one of the busses must follow the
>> specification of the bus. There is no choice. Any additional
>> requirements of the device to deal with external signals must be
>> handled by the device itself and converted to the appropriate bus
>> requirement.
>>
>> This all is configured by the kernel automatically through bus
>> detection and BIOS tables.
>>
>> Thanks,
>>
>>         tglx

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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