Re: [PATCH v2 2/3] Documentation: riscv: Add early boot document

From: Conor Dooley <conor@kernel.org>
To: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: "Albert Ou" <aou@eecs.berkeley.edu>,
	"Jonathan Corbet" <corbet@lwn.net>,
	linux-doc@vger.kernel.org,
	"Song Shuai" <songshuaishuai@tinylab.org>,
	linux-kernel@vger.kernel.org,
	"Conor Dooley" <conor.dooley@microchip.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Björn Töpel" <bjorn@rivosinc.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	linux-riscv@lists.infradead.org,
	"Andrew Jones" <ajones@ventanamicro.com>
Subject: Re: [PATCH v2 2/3] Documentation: riscv: Add early boot document
Date: Thu, 22 Jun 2023 18:41:13 +0100	[thread overview]
Message-ID: <20230622-clone-overfed-21ec0886e904@spud> (raw)
In-Reply-To: <CAHVXubgJQhShbOfaQeOTxM61g_tUnLBxa-0JK+WE+YQRGkYRQA@mail.gmail.com>


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On Thu, Jun 22, 2023 at 07:32:23PM +0200, Alexandre Ghiti wrote:
> On Thu, Jun 22, 2023 at 7:24 PM Andrew Jones <ajones@ventanamicro.com> wrote:
> >
> > On Wed, Jun 21, 2023 at 02:19:50PM +0200, Andrew Jones wrote:
> > > On Wed, Jun 21, 2023 at 09:22:33AM +0200, Alexandre Ghiti wrote:
> > ...
> > > > +Hardware description
> > > > +--------------------
> > > > +
> > > > +The firmware can pass either a devicetree or ACPI tables to the RISC-V kernel.
> > > > +
> > > > +The devicetree is either passed directly to the kernel from the previous stage
> > > > +using the `$a1` register, or when booting with UEFI, it can be passed using the
> > > > +EFI configuration table.
> > > > +
> > > > +The ACPI tables are passed to the kernel using the EFI configuration table. In
> > > > +this case, a tiny devicetree is still created by the EFI stub. Please refer to
> > > > +"EFI stub and devicetree" tree section below for details about this devicetree.
> > >                              ^ redundant 'tree' here
> > >
> >
> > Can whoever applies this drop this 'tree' I pointed while applying?
> 
> Yes, sorry: @Conor Dooley give me the overly long lines you wanted me
> to break and I'll send a v3, it won't take much time and I'll fix this
> too!

Look, I said it was pure pedantry on my part, and not something that
helps with understanding. You've been warned!

diff --git a/Documentation/riscv/boot.rst b/Documentation/riscv/boot.rst
index 019ee818686d..a52793fd9f6c 100644
--- a/Documentation/riscv/boot.rst
+++ b/Documentation/riscv/boot.rst
@@ -143,11 +143,12 @@ be carefully examined.
 Device-tree mapping via fixmap
 ------------------------------
 
-The RISC-V kernel uses the fixmap region to map the devicetree because the
-devicetree virtual mapping must remain the same between :c:func:`setup_vm` and
-:c:func:`setup_vm_final` calls since the :c:var:`reserved_mem` array is
-initialized with virtual addresses established by :c:func:`setup_vm` and used
-with the mapping established by :c:func:`setup_vm_final`.
+
+As the :c:var:`reserved_mem` array is initialized with virtual addresses
+established by :c:func:`setup_vm`, and used with the mapping established by
+:c:func:`setup_vm_final`, the RISC-V kernel uses the fixmap region to map the
+devicetree. This ensures that the same virtual mapping is used by both
+functions.
 
 Pre-MMU execution
 -----------------

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