Message-ID: <1d1bfdc2-f23d-9816-e4e3-ae676105dc39@desertbit.com>
Date:   Tue, 30 Aug 2016 12:08:57 +0200
From:   Roland Singer <roland.singer@...ertbit.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: Kernel Freeze with American Megatrends BIOS

Thanks for pointing it out.

Yeah that's right. The system will hang randomly a few minutes later,
because some certain actions in the graphical user session will trigger
the freeze.

I had a look at the function body of pci_read_config_dword:

  #define PCI_OP_READ(size, type, len) \
  int pci_bus_read_config_##size \
	(struct pci_bus *bus, unsigned int devfn, int pos, type *value)	\
  {									\
	int res;							\
	unsigned long flags;						\
	u32 data = 0;							\
	if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;	\
	raw_spin_lock_irqsave(&pci_lock, flags);			\
	res = bus->ops->read(bus, devfn, pos, len, &data);		\
	*value = (type)data;						\
	raw_spin_unlock_irqrestore(&pci_lock, flags);		\
	return res;							\
  }

I guess, that bus->ops->read(...) might be the trigger.
Any hints how to continue debugging?

Cheers,
Roland

Am 30.08.2016 um 01:54 schrieb Bjorn Helgaas:
> On Mon, Aug 29, 2016 at 09:55:56PM +0200, Roland Singer wrote:
>> Just tried it and the system didn't freeze. However it will freeze
>> after some time (few minutes while working).
>>
>> Seams to be pci_read_config_dword. Where is this exactly defined?
> 
> pci_read_config_dword() is defined in include/linux/pci.h.  It calls
> pci_bus_read_config_dword() which is defined by the PCI_OP_READ() macro
> in drivers/pci/access.c.
> 
> If I understand correctly, this:
> 
>   dis_dev_get();
>   pci_read_config_dword(dis_dev, 0, &cfg_word);
>   dis_dev_put();
> 
> causes an immediate system hang, but if you only do this:
> 
>   dis_dev_get();
>   dis_dev_put();
> 
> the system hangs a few minutes later.  Right?
> 
>> Am 29.08.2016 um 21:07 schrieb Bjorn Helgaas:
>>> On Mon, Aug 29, 2016 at 08:46:17PM +0200, Roland Singer wrote:
>>>> Hi Bjorn,
>>>>
>>>> I am using the bbswitch kernel module to switch off/on the GPU and
>>>> to obtain the GPU power state.
>>>> Obtaining the GPU state immediately after starting the graphical user
>>>> session freezes the system.
>>>>
>>>> This code triggers something, which is responsible for the freeze.
>>>>
>>>> ---
>>>> // Returns 1 if the card is disabled, 0 if enabled
>>>> static int is_card_disabled(void) {
>>>>     u32 cfg_word;
>>>>     // read first config word which contains Vendor and Device ID. If all bits
>>>>     // are enabled, the device is assumed to be off
>>>>     pci_read_config_dword(dis_dev, 0, &cfg_word);
>>>>     // if one of the bits is not enabled (the card is enabled), the inverted
>>>>     // result will be non-zero and hence logical not will make it 0 ("false")
>>>>     return !~cfg_word;
>>>> }
>>>>
>>>> static int bbswitch_proc_show(struct seq_file *seqfp, void *p) {
>>>>     // show the card state. Example output: 0000:01:00:00 ON
>>>>     dis_dev_get();
>>>>     seq_printf(seqfp, "%s %s\n", dev_name(&dis_dev->dev),
>>>>              is_card_disabled() ? "OFF" : "ON");
>>>>     dis_dev_put();
>>>>     return 0;
>>>> }
>>>> ---
>>>>
>>>> Either dis_dev_get or pci_read_config_dword is the trigger.
>>>
>>> What happens if you remove the call to is_card_disabled()?  Does the
>>> system still freeze if you only do the dis_dev_get()/dis_dev_put()?
>>>
>>>> Link to the bbswitch module source code:
>>>> https://github.com/Bumblebee-Project/bbswitch/blob/master/bbswitch.c#L333
>>>>
>>>>
>>>> Am 29.08.2016 um 18:02 schrieb Bjorn Helgaas:
>>>>> [+cc linux-acpi, linux-kernel, dri-devel]
>>>>>
>>>>> Hi Roland,
>>>>>
>>>>> I have no idea how to debug this problem.  Are you seeing something
>>>>> that suggests it may be a PCI problem?
>>>>>
>>>>> On Tue, Aug 23, 2016 at 11:23:45AM +0200, Roland Singer wrote:
>>>>>> Hi,
>>>>>>
>>>>>> hope somebody can help me fix this kernel problem which affects the following machines:
>>>>>>
>>>>>> - Clevo P651RA (i7-6700HQ/GTX 965M, part of the P6xxRx family which are also affected)
>>>>>> - MSI GE62 Apache Pro (i7-6700HQ/GTX 960M)
>>>>>> - Gigabyte P35V5 (i7-6700HQ/GTX 970M)
>>>>>> - Razer Blade 14" (2016) (i7-6700HQ/GTX 970M) (BIOS 5.11, 04/07/2016)
>>>>>>
>>>>>>
>>>>>> The kernel freezes if the graphical user session (Xorg & Wayland) is
>>>>>> started with a switched off discrete GPU card (NVIDIA).
>>>>>> If the discrete GPU is switched off after the graphical session start,
>>>>>> then everything works as expected, until the graphical session is restarted.
>>>>>>
>>>>>> This problem seams to be linked to specific BIOS settings. If the computer
>>>>>> is started with the following command line:
>>>>>>
>>>>>> acpi_osi=! acpi_osi="Windows 2009"
>>>>>>
>>>>>> then the kernel freeze does not occur anymore. However this required a special
>>>>>> ACPI DSDT firmware patch for the Razer Blade 2016 laptop:
>>>>>>
>>>>>> https://github.com/m4ng0squ4sh/razer_blade_14_2016_acpi_dsdt
>>>>>>
>>>>>> I strongly recommend to fix this in the kernel and I am ready to help and solve
>>>>>> this problem with some help.
>>>>>>
>>>>>> Here is a link to the GitHub issue with further information:
>>>>>>
>>>>>> https://github.com/Bumblebee-Project/Bumblebee/issues/764#issuecomment-241212595
>>>>>>
>>>>>> Here are some more detailed information:
>>>>>>
>>>>>> https://github.com/Lekensteyn/acpi-stuff/blob/master/Clevo-P651RA/notes.txt
>>>>>>
>>>>>> Hope somebody can help.
>>>>
>>>> --
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>>

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