linux-kernel - Re: [RFC Patch 09/19] ACPI: Fix a bug in parsing ACPI Memroy24 resource

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Date:	Wed, 21 Jan 2015 10:48:14 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>, Len Brown <lenb@...nel.org>,
	Tony Luck <tony.luck@...el.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [RFC Patch 09/19] ACPI: Fix a bug in parsing ACPI Memroy24 resource

On 2015/1/21 10:59, Rafael J. Wysocki wrote:
> On Wednesday, January 21, 2015 10:15:01 AM Jiang Liu wrote:
>> On 2015/1/21 8:42, Rafael J. Wysocki wrote:
>>> On Thursday, January 08, 2015 10:32:56 AM Jiang Liu wrote:
>>>> According to ACPI spec 5, section 6.4.3.1 "24-Bit Memory Range Descriptor",
>>>> minimum, maximum and address_length field in struct acpi_resource_memory24
>>>> is in granularity of 256-bytes. So shift 8-bit left to get correct address.
>>>
>>> Are you sure about this?
>>>
>>> I'm reading ACPI 5.1 ATM and (on page 316) it only says about the range length
>>> being in 256 byte blocks.
>> Hi Rafael,
>> 	According to ACPI spec 5.a sec 6.4.3.1,
>> Byte 4, "Range minimum base address, _MIN, bits[7:0]", "Address
>> bits[15:8] of the minimum base memory address for which
>> the card may be configured."
>> Byte 5, "Range minimum base address, _MIN, bits[15:8]", "Address
>> bits[23:16] of the minimum base memory address for
>> which the card may be configured".
> 
> Ah, OK.
> 
> So bits [15:0] of the _MIN field are bits [23:8] of the address.  Tricky that.
> 
> I wonder why no problems with that have ever been reported ...
I guess nobody really makes use of this structure:(

> 
>> Byte 10, "Range length, _LEN, bits[7:0]", "This field contains the lower
>> eight bits of the memory range length. The range length provides the
>> length of the memory range in 256 byte blocks."
>> Byte 11, "Range length, _LEN, bits[15:8]", "This field contains the
>> upper eight bits of the memory range length. The range length field
>> provides the length of the memory range in 256 byte blocks."
>>
>> That means _MIN defines bits[23:8] of the minimal address, and _LEN
>> is in granularity of 256 bytes, so shift them left by 8 bits.
>> Regards,
>> Gerry
>>
>>>
>>>> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
>>>> ---
>>>>  drivers/acpi/resource.c |    4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/acpi/resource.c b/drivers/acpi/resource.c
>>>> index abe3a29ad802..f4aeef22a9d8 100644
>>>> --- a/drivers/acpi/resource.c
>>>> +++ b/drivers/acpi/resource.c
>>>> @@ -90,8 +90,8 @@ bool acpi_dev_resource_memory(struct acpi_resource *ares, struct resource *res)
>>>>  	switch (ares->type) {
>>>>  	case ACPI_RESOURCE_TYPE_MEMORY24:
>>>>  		memory24 = &ares->data.memory24;
>>>> -		acpi_dev_get_memresource(res, memory24->minimum,
>>>> -					 memory24->address_length,
>>>> +		acpi_dev_get_memresource(res, memory24->minimum << 8,
>>>> +					 memory24->address_length << 8,
>>>>  					 memory24->write_protect);
>>>>  		break;
>>>>  	case ACPI_RESOURCE_TYPE_MEMORY32:
>>>>
>>>
>> --
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