On 09/14/2017 11:44 AM, Srinath Mannam wrote:
> Hi Jens Axboe,
>
> On Thu, Sep 14, 2017 at 11:05 PM, Jens Axboe <axboe@xxxxxxxxx> wrote:
>> On 09/14/2017 11:28 AM, Srinath Mannam wrote:
>>> Hi Bjorn,
>>>
>>> On Thu, Sep 14, 2017 at 10:52 PM, Jens Axboe <axboe@xxxxxxxxx> wrote:
>>>>
>>>> On 09/14/2017 11:11 AM, Bjorn Helgaas wrote:
>>>>> [+cc linux-pci]
>>>>>
>>>>> On Thu, Sep 14, 2017 at 12:00 PM, Jens Axboe <axboe@xxxxxxxxx> wrote:
>>>>>> On 09/12/2017 02:04 PM, Johannes Berg wrote:
>>>>>>> On Tue, 2017-09-12 at 13:43 -0600, Jens Axboe wrote:
>>>>>>>
>>>>>>>> CC'ing the guilty part and Bjorn. I'm assuming it's the
>>>>>>>> pci_is_enabled() check, since the rest of the patch shouldn't have
>>>>>>>> functional changes.
>>>>>>>
>>>>>>> and pci_enable_bridge() already checks if it's already enabled, but
>>>>>>> still enables mastering in that case if it isn't:
>>>>>>>
>>>>>>> static void pci_enable_bridge(struct pci_dev *dev)
>>>>>>> {
>>>>>>> [...]
>>>>>>> if (pci_is_enabled(dev)) {
>>>>>>> if (!dev->is_busmaster)
>>>>>>> pci_set_master(dev);
>>>>>>> return;
>>>>>>> }
>>>>>>>
>>>>>>> so I guess due to the new check we end up with mastering disabled, and
>>>>>>> thus the firmware can't load since that's a DMA thing?
>>>>>>
>>>>>> Bjorn/Srinath, any input here? This is a regression that prevents wifi
>>>>>> from working on a pretty standard laptop. It'd suck to have this be in
>>>>>> -rc1. Seems like the trivial fix would be:
>>>>>>
>>>>>>
>>>>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>>>>>> index b0002daa50f3..ffbe11dbdd61 100644
>>>>>> --- a/drivers/pci/pci.c
>>>>>> +++ b/drivers/pci/pci.c
>>>>>> @@ -1394,7 +1394,7 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
>>>>>> return 0; /* already enabled */
>>>>>>
>>>>>> bridge = pci_upstream_bridge(dev);
>>>>>> - if (bridge && !pci_is_enabled(bridge))
>>>>>> + if (bridge)
>>> With this change and keeping "mutex_lock(&pci_bridge_mutex);" in
>>> pci_enable_bridge functoin will causes a nexted lock.
>>
>> Took a look, and looks like you are right. That code looks like a mess,
>> fwiw.
>>
>> I'd strongly suggest that the bad commit is reverted until a proper
>> solution is found, since the simple one-liner could potentially
>> introduce a deadlock with your patch applied.
> atomic_inc_return(&dev->enable_cnt) in function
> pci_enable_device_flags enables passed pcie device.
> !pci_is_enabled(bridge) check in "if (bridge &&
> !pci_is_enabled(bridge))" checks for bridge device of previous pcie
> device.
> So it will not stop bus_master of bridge device.
> In your case how many bridges in between endpoint and host bridge?
> Please provide the details about your use case.
It's a bog standard Lenovo X1 Carbon, gen4.
# lspci
00:00.0 Host bridge: Intel Corporation Sky Lake Host Bridge/DRAM Registers (rev 08)
00:02.0 VGA compatible controller: Intel Corporation Sky Lake Integrated Graphics (rev 07)
00:08.0 System peripheral: Intel Corporation Sky Lake Gaussian Mixture Model
00:13.0 Non-VGA unclassified device: Intel Corporation Device 9d35 (rev 21)
00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI (rev 21)
00:1c.0 PCI bridge: Intel Corporation Device 9d10 (rev f1)
00:1c.2 PCI bridge: Intel Corporation Device 9d12 (rev f1)
00:1c.4 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port (rev f1)
00:1f.0 ISA bridge: Intel Corporation Sunrise Point-LP LPC Controller (rev 21)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection I219-LM (rev 21)
04:00.0 Network controller: Intel Corporation Wireless 8260 (rev 3a)
05:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller (rev 01)
# lspci -t
-[0000:00]-+-00.0
+-02.0
+-08.0
+-13.0
+-14.0
+-14.2
+-16.0
+-1c.0-[02]--
+-1c.2-[04]----00.0
+-1c.4-[05]----00.0
+-1f.0
+-1f.2
+-1f.3
+-1f.4
\-1f.6
--
Jens Axboe
