linux-kernel - Re: [PATCHi v2] arc: Mask individual IRQ lines during core INTC init

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Date:   Fri, 25 Aug 2017 17:22:41 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     Vineet Gupta <Vineet.Gupta1@...opsys.com>
CC:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCHi v2] arc: Mask individual IRQ lines during core INTC init

Hi Vineet,

On Fri, 2017-08-25 at 10:13 -0700, Vineet Gupta wrote:
> On 08/25/2017 07:22 AM, Alexey Brodkin wrote:
> > 
> > From: Alexey Brodkin <Alexey.Brodkin@...opsys.com>
> > 
> > ARC cores on reset have all interrupt lines of built-in INTC enabled.
> > Which means once we globally enable interrupts (very early on boot)
> > faulty hardware blocks may trigger an interrupt that Linux kernel
> > cannot handle yet as corresponding handler is not yet installed.
> > 
> > In that case system falls in "interrupt storm" and basically never
> > does anything useful except entering and exiting generic IRQ handling
> > code.
> > 
> > One real example of that kind of problematic hardware is DW GMAC which
> > also has interrupts enabled on reset and if Ethernet PHY informs GMAC
> > about link state, GMAC immediately reports that upstream to ARC core
> > and here we are.
> > 
> > Now with that change we mask all individual IRQ lines making entire
> > system more fool-proof.
> > 
> > [This patch was motivated by Adaptrum platform support]
> > 
> > Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> > Cc: Eugeniy Paltsev <paltsev@...opsys.com>
> > Tested-by: Alexandru Gagniuc <alex.g@...ptrum.com>
> > Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
> 
> v1 was merged in mainline this week - please provide a fixup patch on top of 
> mainline / for-curr !

Ooops, didn't see that.
Will do shortly.

-Alexey