Re: [PATCH v2 0/3] Add support for SBI v0.2

From: Alan Kao <alankao@andestech.com>
To: Atish Patra <Atish.Patra@wdc.com>
Cc: "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"anup@brainfault.org" <anup@brainfault.org>,
	"palmer@sifive.com" <palmer@sifive.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"rppt@linux.ibm.com" <rppt@linux.ibm.com>,
	"hch@infradead.org" <hch@infradead.org>,
	"gary@garyguo.net" <gary@garyguo.net>,
	"paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"allison@lohutok.net" <allison@lohutok.net>
Subject: Re: [PATCH v2 0/3] Add support for SBI v0.2
Date: Tue, 1 Oct 2019 12:58:16 +0800	[thread overview]
Message-ID: <20191001045815.GA6572@andestech.com> (raw)
In-Reply-To: <8683f51f26708a468bcdf16a48db1cffac6c28d8.camel@wdc.com>

On Fri, Sep 27, 2019 at 10:57:45PM +0000, Atish Patra wrote:
> On Fri, 2019-09-27 at 15:19 -0700, Christoph Hellwig wrote:
> > On Thu, Sep 26, 2019 at 05:09:12PM -0700, Atish Patra wrote:
> > > The Supervisor Binary Interface(SBI) specification[1] now defines a
> > > base extension that provides extendability to add future extensions
> > > while maintaining backward compatibility with previous versions.
> > > The new version is defined as 0.2 and older version is marked as
> > > 0.1.
> > > 
> > > This series adds support v0.2 and a unified calling convention
> > > implementation between 0.1 and 0.2. It also adds minimal SBI
> > > functions
> > > from 0.2 as well to keep the series lean. 
> > 
> > So before we do this game can be please make sure we have a clean 0.2
> > environment that never uses the legacy extensions as discussed
> > before?
> > Without that all this work is rather futile.
> > 
> 
> As per our discussion offline, here are things need to be done to
> achieve that.
> 
> 1. Replace timer, sfence and ipi with better alternative APIs
> 	- sbi_set_timer will be same but with new calling convention
> 	- send_ipi and sfence_* apis can be modified in such a way that
> 		- we don't have to use unprivileged load anymore
> 		- Make it scalable
> 
> 2. Drop clear_ipi, console, and shutdown in 0.2.
> 
> We will have a new kernel config (LEGACY_SBI) that can be manually
> enabled if older firmware need to be used. By default, LEGACY_SBI will
> be disabled and kernel with new SBI will be built. We will have to set
> a flag day in a year or so when we can remove the LEGACY_SBI
> completely.
> 
> Let us know if it is not an acceptable approach to anybody.
> I will post a RFC patch with new alternate v0.2 APIs sometime next
> week.
>

Will this legacy option be compatible will bbl?  says, version 1.0.0 or
any earlier ones?

> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv
> 
> -- 
> Regards,
> Atish

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