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From:   Vineet Gupta <vineet.gupta1@synopsys.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>,
        "linux-snps-arc@lists.infradead.org" 
        <linux-snps-arc@lists.infradead.org>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Alexey Brodkin" <alexey.brodkin@synopsys.com>
Subject: Re: [PATCH] ARC: IOC: panic if kernel was started with previously
 enabled IOC
Thread-Topic: [PATCH] ARC: IOC: panic if kernel was started with previously
 enabled IOC
Thread-Index: AQHUW+Pi2l0qN/ga1kOYlHrTlH6D2Q==
Date:   Tue, 16 Oct 2018 17:27:34 +0000
Message-ID: <C2D7FE5348E1B147BCA15975FBA23075012B0AE414@US01WEMBX2.internal.synopsys.com>
References: <20181004131212.16405-1-Eugeniy.Paltsev@synopsys.com>
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On 10/04/2018 06:12 AM, Eugeniy Paltsev wrote:=0A=
> Disabling and reconfiguring of IOC are quite a tricky actions because=0A=
> nobody knows what happens if there're IOC-ahndled tarnsactions in flight=
=0A=
> when we're disabling IOC.=0A=
>=0A=
> And the problem is external DMA masters [that were initialized and set=0A=
> in a bootlaoder that was executed before we got here] might continue=0A=
> to send data to memory even at this point and we have no way to prevent=
=0A=
> that.=0A=
>=0A=
> That said it's much safer to not enable IOC at all anywhere before Linux=
=0A=
> kernel.=0A=
>=0A=
> As we can build u-boot with IOC support (mostly for debugging purposes)=
=0A=
> let's check that kernel was started with disabled IOC regardless of=0A=
> our plans to use it or not.=0A=
>=0A=
> Also while I'm at it, replace hardcoded bits in ARC_REG_IO_COH_PARTIAL=0A=
> and ARC_REG_IO_COH_ENABLE registers by definitions.=0A=
>=0A=
> Inspired by: https://lkml.org/lkml/2018/1/19/557=0A=
>=0A=
=0A=
Applied with updated changelog !=0A=
=0A=
-Vineet=0A=