linux-kernel - Re: [PATCH 1/6] MIPS: remove cpu_has_64bit_gp_regs and cpu_has_64bit

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Message-ID: <20200325083012.GA21605@lst.de>
Date:   Wed, 25 Mar 2020 09:30:12 +0100
From:   Christoph Hellwig <hch@....de>
To:     "Maciej W. Rozycki" <macro@...ux-mips.org>
Cc:     Christoph Hellwig <hch@....de>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Fredrik Noring <noring@...rew.org>, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] MIPS: remove cpu_has_64bit_gp_regs and
 cpu_has_64bit_addresses

On Wed, Mar 25, 2020 at 02:36:57AM +0000, Maciej W. Rozycki wrote:
> On Tue, 24 Mar 2020, Christoph Hellwig wrote:
> 
> > Both macros are always identical to CONFIG_64BIT.
> 
>  I think this abstraction makes sense, especially if we want to support 
> 64-bit CPUs that only support 32-bit segments, i.e. MIPS architecture 
> processors whose CP0.Config.AT=1, or legacy MIPS processors that had a 
> similar limitation, such as the R5900 currently under review.

The only use of cpu_has_64bit_addresses is the choice of the ioremap
code base.  Which ioremap code does the R5900 want to use?  If it
doesn't match CONFIG_64BIT having a config option for the ioremap
implementation seems much more sensible, and can be added with the
R5900 patch set (do you have a link to it?).