On 10/21/2019 11:13 AM, Vidya Sagar wrote:
Hi Sinan / Rafael,
Apologies for the ping again.
Do you guys have any further comments on this?
-Vidya Sagar
On 10/15/2019 5:44 PM, Vidya Sagar wrote:
Hi Sinan / Rafael,
Do you have any further comments on this patch?
- Vidya Sagar
On 10/15/2019 4:40 PM, Sinan Kaya wrote:
+Rafael
On 10/15/2019 2:30 AM, Thierry Reding wrote:
Vidya, can you clarify for which device you're seeing the issues? Sounds
like adding a call to pci_pm_reset() (via pci_reset_function()) at some
point.
Sinan, it looks as if pci_pm_reset() (or any of its callers) is not used
very widely. Is that just because most drivers haven't had a need for it
yet? Or am I missing some core functionality that calls this for every
device anyway?
pci_pm_reset() is there as an alternative reset path. We are not
supposed to call this function. Sorry for giving you wrong direction
here. pci_reset_function() should call it only if there is no other
suitable reset function is found.
I think the PCI core should be putting the device back D0 state as one
of the first actions before enumerating. Wake up could be a combination
of ACPI and/or PCI wake up depending on where your device sits in the
topology.
Yup. It is indeed doing it as part of pci_power_up() in pci.c file.
But, what is confusing to me is the order of the calls.
pci_power_up() has following calls in the same order.
pci_raw_set_power_state(dev, PCI_D0);
pci_update_current_state(dev, PCI_D0);
But, pci_raw_set_power_state() is accessing config space without calling
pci_device_is_present() whereas pci_update_current_state() which is called
later in the flow is calling pci_device_is_present()...!
On the other hand, wake up code doesn't perform the CRS wait. CRS
wait is deferred until the first vendor id read in pci_scan_device().
I see that it already waits for 60 seconds.
Going back to the patch...
I think we need to find the path that actually needs this sleep and
put pci_dev_wait() there.
Following is the path in resume() flow.
[ 36.380726] Call trace:
[ 36.383270] dump_backtrace+0x0/0x158
[ 36.386802] show_stack+0x14/0x20
[ 36.389749] dump_stack+0xb0/0xf8
[ 36.393451] pci_update_current_state+0x58/0xe0
[ 36.398178] pci_power_up+0x60/0x70
[ 36.401672] pci_pm_resume_noirq+0x6c/0x130
[ 36.405669] dpm_run_callback.isra.16+0x20/0x70
[ 36.410248] device_resume_noirq+0x120/0x238
[ 36.414364] async_resume_noirq+0x24/0x58
[ 36.418364] async_run_entry_fn+0x40/0x148
[ 36.422418] process_one_work+0x1e8/0x360
[ 36.426525] worker_thread+0x40/0x488
[ 36.430201] kthread+0x118/0x120
[ 36.433843] ret_from_fork+0x10/0x1c
+++ b/drivers/pci/pci.c
@@ -5905,7 +5905,8 @@ bool pci_device_is_present(struct pci_dev *pdev)
if (pci_dev_is_disconnected(pdev))
return false;
- return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0);
+ return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v,
+ PCI_CRS_TIMEOUT);
}
pci_device_is_present() is a too low-level function and it may not
be allowed to sleep. It uses 0 as timeout value.
