On 11/27/2013 04:32 AM, Rafael J. Wysocki wrote:
On Tuesday, November 26, 2013 01:41:13 PM Mike Qiu wrote:
On 11/14/2013 04:54 PM, Huang Ying wrote:
On Thu, 2013-11-14 at 16:37 +0800, mike wrote:
On 11/14/2013 04:25 PM, Huang Ying wrote:
On Thu, 2013-11-14 at 16:12 +0800, mike wrote:
On 11/14/2013 03:53 PM, Huang Ying wrote:
On Thu, 2013-11-14 at 15:19 +0800, mike wrote:
On 11/14/2013 01:59 PM, Huang Ying wrote:
On Thu, 2013-11-14 at 11:23 +0800, mike wrote:
On 11/14/2013 03:20 AM, Alan Stern wrote:
On Wed, 13 Nov 2013, Bjorn Helgaas wrote:
[+cc Rafael, linux-pm]
On Wed, Nov 13, 2013 at 6:09 AM, mike<qiudayu@xxxxxxxxxxxxxxxxxx> wrote:
Hi Huang Ying,
I see you are the author of this patch, commit id is:
967577b062417b4e4b8e27b711220f4124f5153a
I have a question while I try to understand this patch,
So I would very grateful if you or others can give me some reply.....
............
- rc = ddi->drv->probe(ddi->dev, ddi->id);
+ pm_runtime_get_sync(dev);
+ pci_dev->driver = pci_drv;
^^^^^^^^^^^^^^^^^^^^^^^^^^
I see here you make the driver to initialize before probe,
But I have no idea of why you do this change.....
and I look inside the code, it may be pm_runtime relate??
Yes, it is related to runtime PM. In the PCI subsystem, runtime PM
doesn't do anything unless pci_dev->driver is set. You can see this at
the start of pci_pm_runtime_suspend().
Since we want the driver's probe routine to be able to carry out
runtime PM operations, we have to set pci_dev->driver before the probe
routine runs.
Is there any situations , like in probe state, pci_dev->driver
has been set. the pci_pm_runtime_xxx() has passed
pci_dev->driver NULL check, but at this point, probe fail
occurs, and pci_dev->driver to be set to NULL.
What will happen ? Or this situation will never happen?
I'm confuse about this.
I think that will never happen. Before ->probe(), pm_runtime_get_sync()
is called, so pci_pm_runtime_xxx() will not be called until
pm_runtime_put_noidle() is called in ->probe(). And
should be done as one of the latest actions in
->probe(), after the normal probe actions succeeded.
OK, just as your description, it seems OK.
But this is really a issue as I explained in last email.
So I want to know if there are any side-effect of changing the code
in pci_pm_runtime_xxx()
if (!pci_dev->driver)
return 0;
to
if (!dev->driver)
return 0;
If you make this change, we can not put devices into low power state
(runtime suspend the device) in ->probe(). That is expected in some
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This means dev->driver is NULL ?? but pci_dev->driver is set???
Because if use pci_dev->driver can put into low power state, means
pci_dev->driver is set, but in the situation, use dev->driver will can't,
means dev->driver = null, but I have not find any case that
dev->driver = null, but pci_dev->driver != null;
Sorry I make a mistake here. The dev->driver != null in
local_pci_probe(). We use pci_dev->driver instead of dev->driver in
pci_pm_runtime_xxx() because we want device to be kept in normal power
state (D0) and SUSPENDED state when unbound.The
pm_runtime_put/get_sync in pci_device_remove/local_pci_probe will not
change the power state of the device because of the check in
pci_pm_runtime_xxx().
Yes, you are right, but what am I confuse is that, why check dev->driver
in pci_pm_runtime_xxx() can't keep the device in normal power
state (D0) and SUSPENDED state when unbound.
May be logic issue ?
Because dev->driver is set before local_pci_probe() and cleared after
pci_device_remove(). But we need a flag to be changed in
local_pci_probe() and pci_device_remove().
Hi Ying,
I'm now face one bug, and the root cause is this logic has some problem.
The other component calls the ops in driver during probe state, which a
lot of critical data struct haven't been setup yet.
This never happen in old logic, because dev->driver is unset in probe
state, it can check dev->driver to see if the device diver can work. But
for new logic it is really a big issue.
What is the other component and why is it doing that?
Some component like EEH in Power arch, it need to check whether the
driver is work or not.
In old logic, if probed then dev->driver set, otherwise it will be NULL,
it is safe to do so.
But in new, it has problem, it can call the driver API, which is very
dangerous in probe state, maybe a lot key data structure haven't been
setup yet, this lead to the kernel down and machine reboot. Also this
can be fixed in driver, like check the driver data it self, this
solution needs all the driver fix this issue, It may be a huge program.
So we need a new flag I think, or which old flag can we use to solve
this issue ?
Thanks
Mike
Checking dev->driver may not be a correct way to address this issue anyway.
Thanks!
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