linux-kernel - Re: [PATCH] hwmon, k10temp: Add support for AMD F15h M60h processor

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Date:	Thu, 17 Jul 2014 18:02:17 +0200
From:	Clemens Ladisch <clemens@...isch.de>
To:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>,
	Guenter Roeck <linux@...ck-us.net>
CC:	Borislav Petkov <bp@...en8.de>, jdelvare@...e.de,
	rdunlap@...radead.org, bhelgaas@...gle.com,
	lm-sensors@...sensors.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] hwmon, k10temp: Add support for AMD F15h M60h processor

Aravind Gopalakrishnan wrote:
> On 7/15/2014 4:03 AM, Guenter Roeck wrote:
>> On 07/15/2014 12:41 AM, Clemens Ladisch wrote:
>>> Guenter Roeck wrote:
>>>> On Mon, Jul 14, 2014 at 10:21:51PM +0200, Clemens Ladisch wrote:
>>>>> Borislav Petkov wrote:
>>>>>> On Mon, Jul 14, 2014 at 03:23:08PM -0500, Aravind Gopalakrishnan wrote:
>>>>>>> +    if (boot_cpu_data.x86 == 0x15 && boot_cpu_data.x86_model == 0x60) {
>>>>>>> +        pci_bus_write_config_dword(pdev->bus, PCI_DEVFN(0, 0),
>>>>>>> +                       NB_SMU_IND_ADDR, IND_ADDR_OFFSET);
>>>>>>> +        pci_bus_read_config_dword(pdev->bus, PCI_DEVFN(0, 0),
>>>>>>> +                      NB_SMU_IND_DATA, &regval);
>>>>>
>>>>> How do you prevent races with any other code that accesses some indirect
>>>>> register?
>>>
>>> If there actually is any other code; these indirect SMU registers appear
>>> to be mostly undocumented and to be intended to be used by the BIOS.
>>> (Which makes me wonder why the temperature sensor was moved there.)
>>
>> Scary. Does that mean there is a chance they may get used through ACPI ?
>
> I have been asking internally about this, and looks like it's just a register address change.
> So we probably don't have to worry about this being used elsewhere..

The conflict is about the SMU index register; the question is whether
_any_ of these SMU registers is used elsewhere (in a way that could
happen concurrently).


Regards,
Clemens
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