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

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Message-ID: <20200508122137.GA13177@alpha.franken.de>
Date:   Fri, 8 May 2020 14:21:37 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Paul Burton <paulburton@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, Jiaxun Yang <jiaxun.yang@...goat.com>,
        Alexander Lobakin <alobakin@...nk.ru>,
        Huacai Chen <chenhc@...ote.com>,
        Cedric Hombourger <Cedric_Hombourger@...tor.com>,
        René van Dorst <opensource@...rst.com>,
        Ard Biesheuvel <ardb@...nel.org>, Jessica Yu <jeyu@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/20] mips: Add MIPS Warrior P5600 support

On Fri, May 08, 2020 at 11:32:59AM +0200, Thomas Bogendoerfer wrote:
> 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 ?

nevermind, this would also need a select SYS_HAS_CPU_MIPS32_R5, which
isn't wanted here. So patch is fine as is.

Thomas.

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