linux-kernel - Re: [PATCH v6 10/11] riscv: dts: add initial canmv-k230 and k230-evb dts

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Message-ID: <20240405-election-stubble-6b7e3d530d3c@spud>
Date: Fri, 5 Apr 2024 16:52:27 +0100
From: Conor Dooley <conor@...nel.org>
To: Yangyu Chen <cyy@...self.name>
Cc: Icenowy Zheng <uwu@...nowy.me>, linux-riscv@...ts.infradead.org,
	Damien Le Moal <dlemoal@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Philipp Zabel <p.zabel@...gutronix.de>, linux-gpio@...r.kernel.org,
	linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 10/11] riscv: dts: add initial canmv-k230 and k230-evb
 dts

On Mon, Mar 25, 2024 at 11:10:49AM +0800, Yangyu Chen wrote:
> > On Mar 25, 2024, at 00:23, Icenowy Zheng <uwu@...nowy.me> wrote:
> > 在 2024-03-23星期六的 20:12 +0800，Yangyu Chen写道：
> >> - Svpbmt and T-Head MAEE both supported
> >> 
> >> T-Head C908 does support both Svpbmt and T-Head MAEE for page-based
> >> memory
> >> attributes and is controlled by BIT(21) on CSR.MXSTATUS. The Svpbmt
> >> is used
> >> here for mainline kernel support for K230. If the kernel wants to use
> >> Svpbmt, the M-Mode software should unset BIT(21) of CSR.MXSTATUS
> >> before
> >> entering the S-Mode kernel. Otherwise, the kernel will not boot, as 0
> >> on
> >> T-Head MAEE is NonCachable Memory. Once the kernel switches from bare
> >> metal
> >> to Sv39, It will lose dirty cache line modifications that haven't
> >> been
> >> written back to the memory.
> > 
> > As MXSTATUS has a S-mode read-only mirror known as SXSTATUS, maybe the
> > kernel should detect SXSTATUS to decide whether to use Svpbmt or
> > Xtheadpbmt (BTW Svnapot conflicts with Xtheadpbmt too).
> > 
> 
> Thanks for this hint. I may need to change some code in the T-Head PBMT probe.

For now, I'd rather we just focused on supporting the standard
extensions on this SoC in mainline. I've applied the patches re-doing
the Kconfig options just now, feel free to resend these patches
whenever.

Thanks,
Conor.

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