From: Randy Vinson <rvinson@mvista•com>
To: Sergei Shtylyov <sshtylyov@ru•mvista.com>
Cc: "linuxppc-dev@ozlabs•org" <linuxppc-dev@ozlabs•org>
Subject: Re: [RFC] 85XX: Allow 8259 cascade to share an MPIC interrupt line.
Date: Thu, 07 Jun 2007 12:54:50 -0700 [thread overview]
Message-ID: <4668628A.30401@mvista.com> (raw)
In-Reply-To: <46685F77.7050901@ru.mvista.com>
Sergei Shtylyov wrote:
[snippage]
>> The threaded interrupt system has threaded routines for the 4 standard
>> interrupts types used by the generic IRQ system (fasteoi, edge, level
>> and simple), plus a handler for non-generic interrupts (the ones that
>> still use __do_IRQ.) When interrupts are being threaded and a
>> non-cascaded MPIC interrupt occurs, desc->handler normally points to
>> handle_fasteoi_irq which masks the interrupt source, schedules the
>> corresponding IRQ thread, issues an EOI and returns to the interrupted
>> context. At a later time, the scheduler dispatches the IRQ thread which
>> calls a threaded version of the fasteoi handler. The threaded fasteoi
>> routine processes the action chain and calls .unmask to re-enable the
>> interrupt before returning to the calling thread. Once the interrupt has
>> been unmasked, the entire process is free to repeat as needed.
>
> Oh, you could have really skipped the basics. ;-)
Maybe not. See below.
>
>> After processing a possible 8259 interrupt, the 8259 cascade handler
>> calls handle_fasteoi_irq to perform the actions noted above. However,
>> with the 8259 cascade handler hooked to the interrupt, the threaded IRQ
>> handler doesn't recognize it as one of the 4 standard generic IRQ types
>> and calls the threaded version of do_irq instead of the threaded fasteoi
>> handler.
>
> Ah, that's it!
>
>> Once the threaded do_irq handler completes the action list, it
>> uses the .end routine to restart the interrupt flow. Pointing .end to
>> the standard MPIC unmask routine allows it to balance the interrupt mask
>> operation performed by handle_fasteoi_irq before it scheduled the IRQ
>> thread.
>
> Well, but when MPIC's eoi() method is called then? :-O
It's called from handle_fasteoi_irq as I described in the "basics" ;)
Randy V.
next prev parent reply other threads:[~2007-06-07 19:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-07 0:47 [RFC] 85XX: Allow 8259 cascade to share an MPIC interrupt line Randy Vinson
2007-06-07 15:30 ` Jon Loeliger
2007-06-07 18:04 ` Randy Vinson
2007-06-07 17:14 ` Sergei Shtylyov
2007-06-07 19:25 ` Randy Vinson
2007-06-07 19:41 ` Sergei Shtylyov
2007-06-07 19:54 ` Randy Vinson [this message]
2007-06-07 20:04 ` Sergei Shtylyov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4668628A.30401@mvista.com \
--to=rvinson@mvista$(echo .)com \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=sshtylyov@ru$(echo .)mvista.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox