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Subject: Re: [PATCH] MIPS: Scan the DMI system information
To:     Jean Delvare <jdelvare@suse.de>
References: <5959f904-5c46-30a7-7a4f-17f692aca320@loongson.cn>
 <5c042bd8-40ad-e84f-588d-f3ee56f7216d@loongson.cn>
 <20191107114209.5e4cfa4d@endymion>
Cc:     Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Paul Burton <paulburton@kernel.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        James Hogan <jhogan@kernel.org>,
        Huacai Chen <chenhc@lemote.com>, linux-mips@vger.kernel.org,
        linux-kernel@vger.kernel.org, Yinglu Yang <yangyinglu@loongson.cn>,
        Xuefeng Li <lixuefeng@loongson.cn>
From:   Tiezhu Yang <yangtiezhu@loongson.cn>
Message-ID: <b8a06bc4-d069-e713-9f56-8a6aa24d4eee@loongson.cn>
Date:   Thu, 7 Nov 2019 19:07:25 +0800
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On 11/07/2019 06:42 PM, Jean Delvare wrote:
> On Thu, 7 Nov 2019 17:26:58 +0800, Tiezhu Yang wrote:
>> Sorry to resend this email because the mail list server was denied
>> due to it is not plain text.
>>
>> On 11/07/2019 11:42 AM, Jiaxun Yang wrote:
>>> 于 2019年11月7日 GMT+08:00 上午10:42:23, Tiezhu Yang<yangtiezhu@loongson.cn>  写到:
>>>> 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.
>> Hi Jiaxun,
>>
>> It seems that there is no absolutely better way to handle this case.
>>
>> 1. use conditional compilation in drivers/firmware/dmi_scan.c:
>>
>> #if defined(CONFIG_MACH_LOONGSON64)
>>
>> p = dmi_early_remap(0xFFFE000, 0x10000);
>>
>> #else
>>
>> p = dmi_early_remap(0xF0000, 0x10000);
>>
>> #endif
>>
>>
>> This will influence the common code.
>>
>> 2. use callback function in arch/mips/include/asm/dmi.h:
> I see no reason to go that route if the decision can be made at build
> time. Callback functions are good when the decision is made at run time.
>
>> struct plat_dmi_ops {
>>
>>           void (*early_memremap)(void);
>>
>>           void (*memremap)(void);
>>
>> };
>>
>> extern struct plat_dmi_ops *dmi_ops;
>>
>> void __init *mips_early_memremap(resource_size_t phys_addr, unsigned long size)
>>
>> {
>>
>>           dmi_ops->early_memremap();
>>
>> }
>>
>> void *mips_memremap(resource_size_t offset, size_t size, unsigned long flags)
>>
>> {
>>
>>           dmi_ops->memremap();
>>
>> }
>>
>>
>> we can implement the callback function in various of MIPS platforms,
>> like this:
>>
>> struct plat_dmi_ops loongson3_dmi_ops = {
>>
>>           .early_memremap = loongson3_early_memremap,
>>
>>           .memremap = loongson3_memremap,
>>
>> };
>>
>> register_dmi_ops(&loongson3_dmi_ops);
>>
>> #ifdef CONFIG_DMI
>>
>> void __init *loongson3_early_memremap(resource_size_t phys_addr, unsigned long size)
>>
>> {
>>
>>           if (phys_addr == 0xF0000)
>>
>>                   phys_addr = 0xfffe000;
>>
>>           return (void *)TO_CAC(phys_addr);
>>
>> }
>>
>> void *loongson3_memremap(resource_size_t offset, size_t size, unsigned long flags)
>>
>> {
>>
>>           return (void *)TO_CAC(phys_addr);
>>
>> }
>>
>> #else
>>
>> void __init __iomem *loongson3_early_memremap(u64 phys_addr, unsigned long size)
>>
>> {
>>
>>           return NULL;
>>
>> }
>>
>> void __init __iomem *loongson3_memremap(u64 phys_addr, unsigned long size)
>>
>> {
>>
>>           return NULL;
>>
>> }
>>
>> #endif
>>
>>
>> This will not influence the common code.
>>
>> What do you think?
>>
>>
>> Hi Jean,
>>
>> Could you give some suggestions?
> What about:
>
> #if defined(CONFIG_MACH_LOONGSON64)
> #define SMBIOS_ENTRY_POINT_SCAN_START	0xFFFE000
> #else
> #define SMBIOS_ENTRY_POINT_SCAN_START	0xF0000
> #endif
>
> And then just use SMBIOS_ENTRY_POINT_SCAN_START instead of the raw
> address everywhere it is needed?

OK, good idea, thank you very much!
I will send a v2 patch as soon as possible.

Thanks,

Tiezhu Yang

>