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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 v2] ARC: IOC: panic if kernel was started with
 previously enabled IOC
Thread-Topic: [PATCH v2] ARC: IOC: panic if kernel was started with
 previously enabled IOC
Thread-Index: AQHUcC4rsYY5HtVEO0ekS8lnQMQtuw==
Date:   Tue, 30 Oct 2018 16:05:51 +0000
Message-ID: <C2D7FE5348E1B147BCA15975FBA23075013A5892D6@us01wembx1.internal.synopsys.com>
References: <20181030085421.7657-1-Eugeniy.Paltsev@synopsys.com>
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On 10/30/18 1:54 AM, Eugeniy Paltsev wrote:=0A=
> If IOC was already enabled (due to bootloader) it technically needs to=0A=
> be reconfigured with aperture base,size corresponding to Linux memory=0A=
> map which will certainly be different than uboot's. But disabling and=0A=
> reenabling IOC when DMA might be potentially active is tricky business.=
=0A=
> To avoid random memory issues later, just panic here and ask user to=0A=
> upgrade bootloader to one which doesn't enable IOC.=0A=
>=0A=
> This was actually seen as issue on some of the HSDK board with a version=
=0A=
> of uboot which enabled IOC. There were random issues later with starting=
=0A=
> of X or peripherals etc.=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=
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>=0A=
> ---=0A=
> Changes v1->v2:=0A=
>  * Fix regression: check for IOC existence before accessing to any IOC=0A=
>    register.=0A=
>=0A=
...=0A=
...=0A=
>  		arc_slc_disable();=0A=
>  =0A=
> -	if (is_isa_arcv2() && ioc_enable)=0A=
> +	if (is_isa_arcv2() && ioc_exists)=0A=
>  		arc_ioc_setup();=0A=
=0A=
Folded this hunk into existing patch in for-curr.=0A=
=0A=
Thx,=0A=
-Vineet=0A=