Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Alexey Brodkin <Alexey.Brodkin@synopsys.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Eugeniy Paltsev" <Eugeniy.Paltsev@synopsys.com>,
        "linux-snps-arc@lists.infradead.org" 
        <linux-snps-arc@lists.infradead.org>,
        Vineet Gupta <Vineet.Gupta1@synopsys.com>
Subject: RE: [PATCH v2 1/4] ARC: allow to override default mcpu compiler flag
Thread-Topic: [PATCH v2 1/4] ARC: allow to override default mcpu compiler flag
Thread-Index: AQHWOpc3iGznfJlhwkGtLq/Y8Mt+lajJ1WOg
Date:   Fri, 5 Jun 2020 10:47:57 +0000
Message-ID: <MWHPR1201MB0046338E4B38598FFB5DBCB9A1860@MWHPR1201MB0046.namprd12.prod.outlook.com>
References: <20200604173927.23127-1-Eugeniy.Paltsev@synopsys.com>
 <20200604173927.23127-2-Eugeniy.Paltsev@synopsys.com>
In-Reply-To: <20200604173927.23127-2-Eugeniy.Paltsev@synopsys.com>
Accept-Language: en-US
Content-Language: en-US
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: a6f935d6-a0e0-4908-dd30-08d8093de918
X-MS-Exchange-CrossTenant-originalarrivaltime: 05 Jun 2020 10:47:57.9901
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: c33c9f88-1eb7-4099-9700-16013fd9e8aa
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: RZLSUk8k5RgWonkFQ8PlvNo/JpHlyD4rzV2JGZ7bJDN4QyzWOuYiL6+tv5Cws+gjv1Kk40ocmPgE/Hl+ASaL3A==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR1201MB0063
X-OriginatorOrg: synopsys.com
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Eugeniy,

A couple of minor notes below.

> -----Original Message-----
> From: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> Sent: Thursday, June 4, 2020 8:39 PM
> To: linux-snps-arc@lists.infradead.org; Vineet Gupta <vgupta@synopsys.com=
>
> Cc: linux-kernel@vger.kernel.org; Alexey Brodkin <abrodkin@synopsys.com>;=
 Eugeniy Paltsev
> <paltsev@synopsys.com>
> Subject: [PATCH v2 1/4] ARC: allow to override default mcpu compiler flag
>=20
> Kernel builds set their own default -mcpu for a given ISA build.

We used to use a default "-mcpu" per ARC ISA version (one for ARCompact
and one for ARCv2).

> But that gets in the way of "custom" -mcpu flags from propagating
> into kernel build.

But with more versions of CPUs & SoCs becoming available we want to
be able to fine-tune generated code more precise.

> This will also be used in next patches for HSDK-4xD board support which
> uses a different -mcpu to effect dual issue scheduling.

"...for utilization of the new CPU's dual-issue capabilities"?

> +++ b/arch/arc/Makefile
> @@ -10,8 +10,25 @@ CROSS_COMPILE :=3D $(call cc-cross-prefix, arc-linux- =
arceb-linux-)
>  endif
>=20
>  cflags-y	+=3D -fno-common -pipe -fno-builtin -mmedium-calls -D__linux__
> -cflags-$(CONFIG_ISA_ARCOMPACT)	+=3D -mA7
> -cflags-$(CONFIG_ISA_ARCV2)	+=3D -mcpu=3Dhs38
> +
> +tune-mcpu-def-$(CONFIG_ISA_ARCOMPACT)	:=3D -mA7

I'd suggest to either swap "-mA7" which is being obsoleted with "-mcpu=3Dar=
c700"
right here or as a separate change, otherwise we may soon get ATC700 builds
broken with newer compilers.

-Alexey