linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jens Rottmann <JRottmann@LiPPERTEmbedded.de>
To: Andres Salomon <dilinger@queued.net>,
	Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, linux-geode@lists.infradead.org
Subject: [PATCH] cs5535-clockevt: allow the MFGPT IRQ to be shared
Date: Thu, 22 Dec 2011 17:35:50 +0100	[thread overview]
Message-ID: <4EF35C66.6010402@LiPPERTEmbedded.de> (raw)
In-Reply-To: <20111214104724.292b02d4@queued.net>

cs5535-clockevt: allow the MFGPT IRQ to be shared

Shared timer IRQs are not a good solution, however the Geode platform has no
APIC, IRQs are a scarce resource and there is no technical reason to forbid it
rightaway.  Increased latencies and overhead due to sharing are still better
than a driver refusing to load.

Signed-off-by: Jens Rottmann <JRottmann@LiPPERTEmbedded.de>
---

Hi,

I tested this a bit longer, this time with MFGPT IRQ actually being triggered,
with cs5535-clockevt driver loaded first or second when sharing the IRQ, with
some CPU load or without.

I didn't encounter any negative effects of this change. I did have suspend
problems with cs5535-clockevt, but that was in no way different from before I
applied this patch, it's an unrelated BIOS issue.

Thomas Gleixner wrote:
> No, you can share a timer irq. The other drivers don't have the SHARED
> flag set because they are on exclusive irq lines, ...

Is this an ACK?

> shared irqs suck and you figure that out once you try to
> use that shared timer irq on a preempt-rt enabled kernel.

Or a NACK?  :-|   (I did address this in the commit log.)

The kernel I tested with was 3.2-rc6, CONFIG_SMP=y and CONFIG_PREEMPT=y. As I
said, I didn't notice anything bad happening.

Thanks and have a nice christmas holiday,
Jens

--- linux-3.2-rc6/drivers/clocksource/cs5535-clockevt.c
+++ allow_shared_mfgpt_irq/drivers/clocksource/cs5535-clockevt.c
@@ -133,7 +133,7 @@ static irqreturn_t mfgpt_tick(int irq, v
 
 static struct irqaction mfgptirq  = {
 	.handler = mfgpt_tick,
-	.flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER,
+	.flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER | IRQF_SHARED,
 	.name = DRV_NAME,
 };
 
_


  parent reply	other threads:[~2011-12-22 16:35 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-12-12 15:41 IRQF_TIMER | IRQF_SHARED ? Jens Rottmann
2011-12-12 20:31 ` Andres Salomon
2011-12-12 21:00   ` Martin-Éric Racine
2011-12-12 22:06     ` Andres Salomon
2011-12-12 23:38   ` Thomas Gleixner
2011-12-13 15:49   ` Jens Rottmann
2011-12-14 18:37     ` Jens Rottmann
2011-12-14 18:47       ` Andres Salomon
2011-12-21 15:42         ` [PATCH] cs5535-clockevt: don't ignore MFGPT on SMP-capable kernels Jens Rottmann
2012-01-11 10:10           ` Andres Salomon
2012-01-19 12:57             ` Jens Rottmann
2012-01-23 10:44               ` Andres Salomon
2011-12-21 16:37         ` IRQF_TIMER | IRQF_SHARED ? Jens Rottmann
2011-12-22 16:35         ` Jens Rottmann [this message]
2012-01-11 10:15           ` [PATCH] cs5535-clockevt: allow the MFGPT IRQ to be shared Andres Salomon
2012-01-30 13:51         ` [PATCH] cs5535-clockevt: don't ignore MFGPT on SMP-capable kernels Jens Rottmann
2012-01-30 13:59         ` [PATCH] cs5535-clockevt: allow the MFGPT IRQ to be shared Jens Rottmann
2012-02-06  8:20         ` [PATCH resend] cs5535-clockevt: don't ignore MFGPT on SMP-capable kernels Jens Rottmann
2012-02-06  8:23         ` [PATCH resend] cs5535-clockevt: allow the MFGPT IRQ to be shared Jens Rottmann
2011-12-19 14:32       ` "clockevents: Set noop handler in clockevents_exchange_device()" causes hang with cs5535-clockevt Jens Rottmann

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=4EF35C66.6010402@LiPPERTEmbedded.de \
    --to=jrottmann@lippertembedded.de \
    --cc=dilinger@queued.net \
    --cc=linux-geode@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).