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From:   Jonas Gorski <jonas.gorski@gmail.com>
Date:   Mon, 3 Feb 2020 15:46:59 +0100
Message-ID: <CAOiHx==FfiQoFA9cESSni_izS=m+mm7G+gk_tei5XFnKrgurew@mail.gmail.com>
Subject: Re: [PATCH v2,RESEND] MIPS: Scan the DMI system information
To:     Tiezhu Yang <yangtiezhu@loongson.cn>
Cc:     Paul Burton <paulburton@kernel.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        Jean Delvare <jdelvare@suse.com>,
        Huacai Chen <chenhc@lemote.com>,
        Xuefeng Li <lixuefeng@loongson.cn>, linux-mips@vger.kernel.org,
        linux-kernel@vger.kernel.org, Yinglu Yang <yangyinglu@loongson.cn>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
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Hi,

On Thu, 16 Jan 2020 at 14:28, Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
> Enable DMI scanning on the MIPS architecture, this setups DMI identifiers
> (dmi_system_id) for printing it out on task dumps and prepares DIMM entry
> information (dmi_memdev_info) from the SMBIOS table. With this patch, the
> driver can easily match various of mainboards.
>
> In the SMBIOS reference specification, the table anchor string "_SM_" is
> present in the address range 0xF0000 to 0xFFFFF on a 16-byte boundary,
> but there exists a special case for Loongson platform, when call function
> dmi_early_remap, it should specify the start address to 0xFFFE000 due to
> it is reserved for SMBIOS and can be normally access in the BIOS.
>
> This patch works fine on the Loongson 3A3000 platform which belongs to
> MIPS architecture and has no influence on the other architectures such
> as x86 and ARM.
>
> Co-developed-by: Yinglu Yang <yangyinglu@loongson.cn>
> Signed-off-by: Yinglu Yang <yangyinglu@loongson.cn>
> [jiaxun.yang@flygoat.com: Refine definitions and Kconfig]
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> Reviewed-by: Huacai Chen <chenhc@lemote.com>
> ---
>
> v2:
>   - add SMBIOS_ENTRY_POINT_SCAN_START suggested by Jean
>   - refine definitions and Kconfig by Jiaxun
>
>  arch/mips/Kconfig           | 10 ++++++++++
>  arch/mips/include/asm/dmi.h | 20 ++++++++++++++++++++
>  arch/mips/kernel/setup.c    |  2 ++
>  drivers/firmware/dmi_scan.c |  6 +++++-
>  4 files changed, 37 insertions(+), 1 deletion(-)
>  create mode 100644 arch/mips/include/asm/dmi.h
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 4b83507..c097f78 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -2773,6 +2773,16 @@ config HW_PERF_EVENTS
>           Enable hardware performance counter support for perf events. If
>           disabled, perf events will use software events only.
>
> +config DMI
> +       default y if MACH_LOONGSON64
> +       select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
> +       bool "Enable DMI scanning"

Is this option harmless to enable for other MIPS platforms? What
happens if it is enabled on devices where PHYS_OFFSET isn't 0, so
0xF0000 is likely not backed by anything and accessing it might hang
the system?

This probably should depend on MACH_LOONGSON64.

Regards

Jonas