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Subject: Re: [PATCH] MIPS: Scan the DMI system information
To:     Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Paul Burton <paulburton@kernel.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        James Hogan <jhogan@kernel.org>
References: <1573056341-21159-1-git-send-email-yangtiezhu@loongson.cn>
 <480995AF-A678-479F-A3EA-11662474E600@flygoat.com>
Cc:     linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        Yinglu Yang <yangyinglu@loongson.cn>
From:   Tiezhu Yang <yangtiezhu@loongson.cn>
Message-ID: <7aa12639-b94e-e3db-647f-ec1d399fbffd@loongson.cn>
Date:   Thu, 7 Nov 2019 10:42:23 +0800
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On 11/07/2019 08:35 AM, Jiaxun Yang wrote:
>
> 于 2019年11月7日 GMT+08:00 上午12:05:41, Tiezhu Yang <yangtiezhu@loongson.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@loongson.cn>
>> Signed-off-by: Yinglu Yang <yangyinglu@loongson.cn>
>> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.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.

Hi Jiaxun,

Thanks for your review. I agree with you, let me think about it and try to
find a proper way, and then I will send a v2 patch.

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

CONFIG_DMI is set to y by default, I think there is no need to select 
DMI when
set CONFIG_MACH_LOONGSON64.

Thanks,

Tiezhu Yang

>
> Thanks.
>