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From: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
To: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Cc: Vineet Gupta <Vineet.Gupta1@synopsys.com>,
	"linux-snps-arc@lists.infradead.org"
	<linux-snps-arc@lists.infradead.org>,
	Eugeniy  Paltsev <Eugeniy.Paltsev@synopsys.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2 1/4] ARC: allow to override default mcpu compiler flag
Date: Fri, 5 Jun 2020 10:47:57 +0000
Message-ID: <MWHPR1201MB0046338E4B38598FFB5DBCB9A1860@MWHPR1201MB0046.namprd12.prod.outlook.com> (raw)
In-Reply-To: <20200604173927.23127-2-Eugeniy.Paltsev@synopsys.com>

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
> 
> 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 := $(call cc-cross-prefix, arc-linux- arceb-linux-)
>  endif
> 
>  cflags-y	+= -fno-common -pipe -fno-builtin -mmedium-calls -D__linux__
> -cflags-$(CONFIG_ISA_ARCOMPACT)	+= -mA7
> -cflags-$(CONFIG_ISA_ARCV2)	+= -mcpu=hs38
> +
> +tune-mcpu-def-$(CONFIG_ISA_ARCOMPACT)	:= -mA7

I'd suggest to either swap "-mA7" which is being obsoleted with "-mcpu=arc700"
right here or as a separate change, otherwise we may soon get ATC700 builds
broken with newer compilers.

-Alexey

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Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-04 17:39 [PATCH v2 0/4] ARC: [plat-hsdk-4xd] initial port for HSDK-4xD board Eugeniy Paltsev
2020-06-04 17:39 ` [PATCH v2 1/4] ARC: allow to override default mcpu compiler flag Eugeniy Paltsev
2020-06-04 18:27   ` Vineet Gupta
2020-06-05 10:47   ` Alexey Brodkin [this message]
2020-06-16 22:12     ` Vineet Gupta
2020-06-04 17:39 ` [PATCH v2 2/4] ARC: ARCv2: support loop buffer (LPB) disabling Eugeniy Paltsev
2020-06-18 19:50   ` Eugeniy Paltsev
2020-06-18 20:00     ` Vineet Gupta
2020-06-04 17:39 ` [PATCH v2 3/4] ARC: [plat-hsdk-4xd] initial port for HSDK-4xD board Eugeniy Paltsev
2020-06-04 22:02   ` Rob Herring
2020-06-04 17:39 ` [PATCH v2 4/4] ARC: [plat-hsdk*] document HSDK-4xD board/SoC bindings Eugeniy Paltsev
2020-06-04 20:00 ` [PATCH v2 0/4] ARC: [plat-hsdk-4xd] initial port for HSDK-4xD board Vineet Gupta

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