linux-kernel - Re: [PATCH] MIPS: disable MMID if GINVT is not usable

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Message-ID: <aGUhUM1y-ZLGWZg-@alpha.franken.de>
Date: Wed, 2 Jul 2025 14:08:48 +0200
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Jiaxun Yang <jiaxun.yang@...goat.com>
Cc: Gregory CLEMENT <gregory.clement@...tlin.com>,
	Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
	Théo Lebrun <theo.lebrun@...tlin.com>,
	Tawfik Bayouk <tawfik.bayouk@...ileye.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	"linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: disable MMID if GINVT is not usable

On Wed, Jun 25, 2025 at 03:44:00PM +0100, Jiaxun Yang wrote:
> 在2025年6月25日周三 下午2:27，Gregory CLEMENT写道：
> 
> Hi Gregory,
> 
> > If System-level Interconnect (aka Network on Chip) does not support
> > the global invalidation, then MMID feature is not usable. Indeed the
> > current implementation of MMID relies on the GINV* instruction.
> 
> Yes, it is the case if the NoC IP can't handle AMBA ACE DVM requests.
> 
> >
> > Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
> > ---
> >  arch/mips/Kconfig                    | 6 ++++++
> >  arch/mips/include/asm/cpu-features.h | 5 ++++-
> >  arch/mips/mobileye/Kconfig           | 2 ++
> >  3 files changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> > index 
> > 1e48184ecf1ec8e29c0a25de6452ece5da835e30..05ce008459b89f03fa71d94429607feb9d06526f 
> > 100644
> > --- a/arch/mips/Kconfig
> > +++ b/arch/mips/Kconfig
> > @@ -2575,6 +2575,12 @@ config WAR_R10000_LLSC
> >  config WAR_MIPS34K_MISSED_ITLB
> >  	bool
> > 
> > +# Some I6500 based SoC do not support the global invalidation on their
> > +# System-level Interconnect (aka Network on Chip), this have an
> > +# influence on the MMID support.
> > +config GINVT_UNSUPPORTED_NOC
> > +	bool
> > +
> 
> I believe this should be a DeviceTree property of CM node instead of Kconfig
> hack.

Either that or by a runtime check, if possible.

Thomas.

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