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Wysocki" , "Rafael J . Wysocki" , Tom Rix , Conor Dooley , Weili Qian , Herbert Xu , Jonathan Corbet , Marc Zyngier , Daniel Lezcano , Andrew Jones , Albert Ou , Mark Gross , Hans de Goede , Paul Walmsley , Thomas Gleixner , Nathan Chancellor , Nick Desaulniers , Zhou Wang , Palmer Dabbelt , Len Brown , Maximilian Luz , "David S . Miller" Subject: Re: [PATCH V4 19/23] RISC-V: Add ACPI initialization in setup_arch() Message-ID: References: <20230404182037.863533-1-sunilvl@ventanamicro.com> <20230404182037.863533-20-sunilvl@ventanamicro.com> <20230404-escalator-fridge-daf9aaffad12@spud> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230404-escalator-fridge-daf9aaffad12@spud> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Tue, Apr 04, 2023 at 10:38:56PM +0100, Conor Dooley wrote: > On Tue, Apr 04, 2023 at 11:50:33PM +0530, Sunil V L wrote: > > Initialize the ACPI core for RISC-V during boot. > > > > ACPI tables and interpreter are initialized based on > > the information passed from the firmware and the value of > > the kernel parameter 'acpi'. > > > > With ACPI support added for RISC-V, the kernel parameter 'acpi' > > is also supported on RISC-V. Hence, update the documentation. > > > > Signed-off-by: Sunil V L > > Acked-by: Rafael J. Wysocki > > Reviewed-by: Andrew Jones > > Acked-by: Conor Dooley > > > + /* Parse the ACPI tables for possible boot-time configuration */ > > + acpi_boot_table_init(); > > + if (acpi_disabled) { > > + if (IS_ENABLED(CONFIG_BUILTIN_DTB)) { > > + unflatten_and_copy_device_tree(); > > + } else { > > + if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa)))) > > + unflatten_device_tree(); > > + else > > + pr_err("No DTB found in kernel mappings\n"); > > + } > > + } else { > > + early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa))); > > I'm probably forgetting something, but this seems very non-obvious to > me: > Why are you running early_init_dt_verify() when ACPI is enabled? > I think that one deserves a comment so that next time someone looks at > this (that doesn't live in ACPI land) they've know exactly why this is > like it is. > > Doubly so since this is likely to change with some of Alex's bits moving > the dtb back into the fixmap. > Good question. The kernel creates a tiny DTB even when the FW didn't pass the FDT (ACPI systems). Please see update_fdt(). So, parse_dtb() would have set initial_boot_params to early VA and if we don't call early_init_dt_verify() again with __va, it panics since initial_boot_params can not be translated. Thanks, Sunil