linux-kernel - Re: m68k: [v5] Convert to genirq (WIP)

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Date:	Sun, 28 Aug 2011 12:08:11 +1000 (EST)
From:	Finn Thain <fthain@...egraphics.com.au>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
cc:	Linux/m68k <linux-m68k@...r.kernel.org>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: m68k: [v5] Convert to genirq (WIP)


On Fri, 26 Aug 2011, Geert Uytterhoeven wrote:

> - [PATCH 18/24]: m68k/mac: Optimize interrupts using chain handlers (NEW)

That patch has a mistake --

	irq_set_chained_handler(IRQ_AUTO_4, psc_irq);
	irq_set_handler_data(IRQ_AUTO_3, (void *)0x40);
	irq_set_chained_handler(IRQ_AUTO_5, psc_irq);
	irq_set_handler_data(IRQ_AUTO_3, (void *)0x50);
	irq_set_chained_handler(IRQ_AUTO_6, psc_irq);
	irq_set_handler_data(IRQ_AUTO_3, (void *)0x60);

should be

	irq_set_chained_handler(IRQ_AUTO_4, psc_irq);
	irq_set_handler_data(IRQ_AUTO_4, (void *)0x40);
	irq_set_chained_handler(IRQ_AUTO_5, psc_irq);
	irq_set_handler_data(IRQ_AUTO_5, (void *)0x50);
	irq_set_chained_handler(IRQ_AUTO_6, psc_irq);
	irq_set_handler_data(IRQ_AUTO_6, (void *)0x60);

I also found that the mac_esp driver probe (when in PIO mode) locks up the 
machine. I worked around this by changing the 
disable_irq(IRQ_VIA2_3)/enable_irq(IRQ_VIA2_3) calls to 
local_irq_save/local_irq_restore, but this is not a good solution.

Apparently genirq doesn't permit nested disable_irq/enable_irq calls. But 
I haven't found any outer disable_irq/enable_irq pair yet, so I'm only 
guessing as to the cause of the problem. I'll keep looking.

On one VIA-based machine that I tested, !CONFIG_USE_GENERIC_HARDIRQS 
gives:

# cat /proc/interrupts
auto       1:       2299 via1
auto       2:       3876 via2
auto       4:        562 SCC
auto       7:          0 NMI
mac       10:        590 pmu-shift
mac       12:         90 pmu-clock
mac       14:       1635 timer
mac       17:       3876 nubus
mac       56:       3879 sonic

whereas, CONFIG_USE_GENERIC_HARDIRQS=y gives:

# cat /proc/interrupts
           CPU0       
  4:       5303      auto  SCC
  7:          0      auto  NMI
 10:       2136       mac  pmu-shift
 12:        607       mac  pmu-clock
 14:      41858       mac  timer
 56:      66876       mac  sonic
ERR:          0

Are there no counters for chained IRQs?

Other than these issues everything looks OK. I will test OSS and Baboon 
when I get the relevant hardware set up.

Finn
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