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

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Date:	Thu, 17 Jul 2014 10:22:41 -0500
From:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
To:	Guenter Roeck <linux@...ck-us.net>,
	Clemens Ladisch <clemens@...isch.de>
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

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?
>>>>
>>> I just wanted to ask exactly the same question. I think this will need
>>> locking.
>>
>> 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..

>
>> Anyway, if a lock is needed, it looks as if it could go into a helper
>> function such as "amd_nb_smu_ind_read()" in arch/x86/kernel/amd_nb.c.
>>
> Yes, something like that.
>
>
Okay, I shall add the locking mechanism and re-send.

Thanks,
-Aravind.

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