Re: [PATCH v2 07/20] mips: Add MIPS Warrior P5600 support

From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: "Alexey Malahov" <Alexey.Malahov@baikalelectronics.ru>,
	"Paul Burton" <paulburton@kernel.org>,
	"Ralf Baechle" <ralf@linux-mips.org>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Rob Herring" <robh+dt@kernel.org>,
	linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
	"Jiaxun Yang" <jiaxun.yang@flygoat.com>,
	"Alexander Lobakin" <alobakin@dlink.ru>,
	"Huacai Chen" <chenhc@lemote.com>,
	"Cedric Hombourger" <Cedric_Hombourger@mentor.com>,
	"René van Dorst" <opensource@vdorst.com>,
	"Ard Biesheuvel" <ardb@kernel.org>,
	"Jessica Yu" <jeyu@kernel.org>,
	"Masahiro Yamada" <masahiroy@kernel.org>,
	linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 07/20] mips: Add MIPS Warrior P5600 support
Date: Fri, 8 May 2020 11:32:59 +0200	[thread overview]
Message-ID: <20200508093259.GB9085@alpha.franken.de> (raw)
In-Reply-To: <20200507211923.kfu2ly3ncqms4c2u@mobilestation>

On Fri, May 08, 2020 at 12:19:23AM +0300, Serge Semin wrote:
> On Thu, May 07, 2020 at 01:17:35PM +0200, Thomas Bogendoerfer wrote:
> > P5600 is CPU_MIPS_R5 so can't you select it here and drop all the || CPU_5600
> > above/below ?
> 
> Alas, We can't do this so easy. CONFIG_CPU_MIPS32_{R2,R5,R6} and any other
> CONFIG_CPU_* configs is something that kernel config-file is supposed to select.
> Their availability is enabled by the CONFIG_SYS_HAS_CPU_* configs. CONFIG_CPU_*
> is supposed to activate CPU-specific features and there is only one
> CONFIG_CPU_x can be enabled at a time seeing it's a part of the "CPU type"
> choice kconfig menu. In addition the CPU config also tunes a compiler to activate
> the arch-specific ISA and optimizations in the arch/mips/Makefile by setting
> -march=cpu-name (where cpu-name can be p5600, mips32r5, etc).
> 
> Yes, P5600 is based on the MIPS32r5, but it also has got some specific features
> (see config CPU_P5600 and config MIPS32_R5), which makes it to be different from
> the ancestor. So In addition to the difficulties described above IMHO converting
> CPU_P5600 to a set of features activated on top of the CPU_MIPS32_R5 config
> would contradict the design of the CPU-support configs implemented in the MIPS
> arch subsystem.

maybe I wasn't clear enough, my suggestion is

use 

config CPU_P5600
	bool "MIPS Warrior P5600"
	depends on SYS_HAS_CPU_P5600
	select CPU_MIPS32_R5
	select CPU_SUPPORTS_UNCACHED_ACCELERATED
	select CPU_SUPPORTS_CPUFREQ
	select CPU_MIPSR2_IRQ_VI
	select CPU_MIPSR2_IRQ_EI

That way you don't need to any "|| CPU_P5600" where CPU_MIPS32_R5 is
already there. Or are there cases, where this would be wrong ?

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]