linux-kernel - Re: [PATCH] MIPS: Scan the DMI system information

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Date:   Thu, 07 Nov 2019 08:35:48 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Paul Burton <paulburton@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>
CC:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yinglu Yang <yangyinglu@...ngson.cn>
Subject: Re: [PATCH] MIPS: Scan the DMI system information



于 2019年11月7日 GMT+08:00 上午12:05:41, Tiezhu Yang <yangtiezhu@...ngson.cn> 写到:
>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.
>
>Co-developed-by: Yinglu Yang <yangyinglu@...ngson.cn>
>Signed-off-by: Yinglu Yang <yangyinglu@...ngson.cn>
>Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
>---
> arch/mips/Kconfig           | 12 ++++++++++++
>arch/mips/include/asm/dmi.h | 43
>+++++++++++++++++++++++++++++++++++++++++++
> arch/mips/kernel/setup.c    |  2 ++
> 3 files changed, 57 insertions(+)
> create mode 100644 arch/mips/include/asm/dmi.h
>
>diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
>index 7cb8947..0a67b18 100644
>--- a/arch/mips/Kconfig
>+++ b/arch/mips/Kconfig
>@@ -2757,6 +2757,18 @@ config HW_PERF_EVENTS
> 	  Enable hardware performance counter support for perf events. If
> 	  disabled, perf events will use software events only.
> 
>+# Mark as expert because too many people got it wrong.
>+# The code disables itself when not needed.
>+config DMI
>+	default y
>+	select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
>+	bool "Enable DMI scanning" if EXPERT
>+	help
>+	  Enabled scanning of DMI to identify machine quirks. Say Y
>+	  here unless you have verified that your setup is not
>+	  affected by entries in the DMI blacklist. Required by PNP
>+	  BIOS code.
>+
> config SMP
> 	bool "Multi-Processing support"
> 	depends on SYS_SUPPORTS_SMP
>diff --git a/arch/mips/include/asm/dmi.h b/arch/mips/include/asm/dmi.h
>new file mode 100644
>index 0000000..1f3da37
>--- /dev/null
>+++ b/arch/mips/include/asm/dmi.h
>@@ -0,0 +1,43 @@
>+/* SPDX-License-Identifier: GPL-2.0 */
>+#ifndef _ASM_MIPS_DMI_H
>+#define _ASM_MIPS_DMI_H
>+
>+#define dmi_early_remap		mips_early_memremap
>+#define dmi_early_unmap		mips_early_memunmap
>+#define dmi_remap(_x, _l)	mips_memremap(_x, _l, MEMREMAP_WB)
>+#define dmi_unmap(_x)		mips_memunmap(_x)
>+
>+#define dmi_alloc(l)		memblock_alloc_low(l, PAGE_SIZE)
>+
>+void __init *mips_early_memremap(resource_size_t phys_addr, unsigned
>long size)
>+{
>+#if defined(CONFIG_MACH_LOONGSON64)
>+	if (phys_addr == 0xF0000)
>+		phys_addr = 0xFFFE000;
>+
>+	return (void *)TO_CAC(phys_addr);
>+#else
>+	return NULL;
>+#endif
>+}

Hi Tiezhu,

It is really tricky to hijack dmi address here during remap.
I think we should set the dmi table address at  dmi_scan.c by a marco or something else rather than hijack it during remap.

Btw: Probably we should set DMI default y when MACH_LOONGSON64 is set?

Thanks.

-- 
Jiaxun Yang