Re: [PATCH 3/5] PCI: revert preparing for wakeup in runtime-suspend finalization

[Konstantin Khlebnikov <khlebnikov@openvz.org>]

Rafael J. Wysocki wrote:
> On Saturday, February 02, 2013 09:58:45 PM Rafael J. Wysocki wrote:
>> On Saturday, February 02, 2013 04:12:03 PM Konstantin Khlebnikov wrote:
>>> Rafael J. Wysocki wrote:
>>>> On Tuesday, January 29, 2013 12:55:15 PM Rafael J. Wysocki wrote:
>>>>> On Tuesday, January 29, 2013 11:04:57 AM Konstantin Khlebnikov wrote:
>>>>>> Rafael J. Wysocki wrote:
>>>>>>> On Monday, January 28, 2013 04:17:42 PM Bjorn Helgaas wrote:
>>>>>>>> [+cc Rafael]
>>>>>>>>
>>>>>>>> On Fri, Jan 18, 2013 at 4:42 AM, Konstantin Khlebnikov
>>>>>>>> <khlebnikov@openvz.org>    wrote:
>>>>>>>>> This patch effectively reverts commit 42eca2302146fed51335b95128e949ee6f54478f
>>>>>>>>> ("PCI: Don't touch card regs after runtime suspend D3")
>>>>>>>>>
>>>>>>>>> | This patch checks whether the pci state is saved and doesn't attempt to hit
>>>>>>>>> | any registers after that point if it is.
>>>>>>>>>
>>>>>>>>> This seems completely wrong. Yes, PCI configuration space has been saved by
>>>>>>>>> driver, but this doesn't means that all job is done and device has been
>>>>>>>>> suspended and ready for waking up in the future.
>>>>>>>>>
>>>>>>>>> For example driver e1000e for ethernet in my thinkpad x220 saves pci-state
>>>>>>>>> but device cannot wakeup after that, because it needs some ACPI callbacks
>>>>>>>>> which usually called from pci_finish_runtime_suspend().
>>>>>>>>>
>>>>>>>>> | Optimus (dual-gpu) laptops seem to have their own form of D3cold, but
>>>>>>>>> | unfortunately enter it on normal D3 transitions via the ACPI callback.
>>>>>>>>>
>>>>>>>>> Hardware which disappears from the bus unexpectedly is exception, so let's
>>>>>>>>> handle it as an exception. Its driver should set device state to D3cold and
>>>>>>>>> the rest code will handle it properly.
>>>>>>>>
>>>>>>>> Functions in D3cold don't have power, so it's completely expected that
>>>>>>>> they would disappear from the bus and not respond to config accesses.
>>>>>>>> Maybe Dave was referring to D3hot, where functions *should* respond to
>>>>>>>> config accesses.  I dunno.
>>>>>>>>
>>>>>>>> Just to be clear, it sounds like 42eca230 caused a regression on your
>>>>>>>> e1000e device?  If so, I guess we should revert it unless you and Dave
>>>>>>>> can figure out a better patch that fixes both your e1000e device and
>>>>>>>> the Optimus issue.
>>>>>>>
>>>>>>> Yes, if there's a regression, let's revert it, but I'd like the regression
>>>>>>> to be described clearly.
>>>>>>
>>>>>> Yep, this is regression.
>>>>>>
>>>>>> commit 42eca2302146fed51335b95128e949ee6f54478f ("PCI: Don't touch
>>>>>> card regs after runtime suspend D3") changes state convention during
>>>>>> runtime-suspend transaction too much. If PCI configuration space
>>>>>> has been saved by driver that does not means that all job is done
>>>>>> and device has been suspended and ready for waking up in the future.
>>>>>>
>>>>>> e1000e saves pci-config space itself, but it requires operations which
>>>>>> pci_finish_runtime_suspend() does: preparing for wake (calling particular
>>>>>> platform pm-callbacks) and switching to proper sleep state.
>>>>>
>>>>> Well, I'd argue this is a bug in e1000e.  Why does it need to save the PCI
>>>>> config space even though pci_pm_runtime_suspend() will do that anyway?
>>>>
>>>> I honestly don't think we should revert 42eca2302146 because of this.
>>>>
>>>> Yes, there is a requirement that drivers not save the PCI config space by
>>>> themselves unless they want to do the whole power management by themselves too
>>>> and e1000e is not following that.  So either we need to drop the
>>>> pci_save_state() from __e1000_shutdown() which I would prefer (I'm not really
>>>> sure why it is there), or e1000_runtime_suspend() needs to call
>>>> pci_finish_runtime_suspend() by itself.
>>>
>>> Yet another problem: some drivers calls pci_save_state() from ->probe() callback
>>> to use this saved state in pci_error_handlers->slot_reset().
>>> As result pdev->state_saved is true mostly all time.
>>> At least e1000e and drivers/pci/pcie/portdrv_pci.c are doing this.
>>>
>>> I think it will be safer to revert 42eca2302146 in v3.8
>>
>> Well, I wonder if we can just do something like the appended patch instead and
>> address the e1000e runtime suspend by calling pci_finish_runtime_suspend()
>> directly from e1000_runtime_suspend().
>>
>> While we can revert commit 42eca2302146, that hardly would be progress,
>> because then the issue it was supposed to address would still need to be
>> addressed somehow.
>>
>> ---
>>   drivers/pci/pci-driver.c |    4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> Index: linux-pm/drivers/pci/pci-driver.c
>> ===================================================================
>> --- linux-pm.orig/drivers/pci/pci-driver.c
>> +++ linux-pm/drivers/pci/pci-driver.c
>> @@ -628,6 +628,7 @@ static int pci_pm_suspend(struct device
>>   		goto Fixup;
>>   	}
>>
>> +	pci_dev->state_saved = false;
>>   	if (pm->suspend) {
>>   		pci_power_t prev = pci_dev->current_state;
>>   		int error;
>> @@ -774,6 +775,7 @@ static int pci_pm_freeze(struct device *
>>   		return 0;
>>   	}
>>
>> +	pci_dev->state_saved = false;
>>   	if (pm->freeze) {
>>   		int error;
>>
>> @@ -862,6 +864,7 @@ static int pci_pm_poweroff(struct device
>>   		goto Fixup;
>>   	}
>>
>> +	pci_dev->state_saved = false;
>>   	if (pm->poweroff) {
>>   		int error;
>>
>> @@ -987,6 +990,7 @@ static int pci_pm_runtime_suspend(struct
>>   	if (!pm || !pm->runtime_suspend)
>>   		return -ENOSYS;
>>
>> +	pci_dev->state_saved = false;
>>   	pci_dev->no_d3cold = false;
>>   	error = pm->runtime_suspend(dev);
>>   	suspend_report_result(pm->runtime_suspend, error);
>
> For completness, on top of the above one.

I would prefer to remove pci_save_state() from e1000e_runtime_suspend().

--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -5429,9 +5429,11 @@ static int __e1000_shutdown(struct pci_dev *pdev, bool *enable_wake,
         }
         e1000e_reset_interrupt_capability(adapter);

-       retval = pci_save_state(pdev);
-       if (retval)
-               return retval;
+       if (!runtime) {
+               retval = pci_save_state(pdev);
+               if (retval)
+                       return retval;
+       }

         status = er32(STATUS);
         if (status & E1000_STATUS_LU)

I found another problem in e1000e: it does not calls pci_enable_master()
in 'resume' functions, but it disables 'bus-mastering' on suspending.
Thus if pci_save_state() is called after clearing that bit whole device
wouldn't work after resuming.

--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -5598,6 +5598,7 @@ static int __e1000_resume(struct pci_dev *pdev)

         pci_set_power_state(pdev, PCI_D0);
         pci_restore_state(pdev);
+       pci_set_master(pdev);
         pci_save_state(pdev);

         err = pci_enable_device_mem(pdev);

>
> ---
>   drivers/net/ethernet/intel/e1000e/netdev.c |    1 +
>   drivers/pci/pci.c                          |    1 +
>   drivers/pci/pci.h                          |    1 -
>   include/linux/pci.h                        |    1 +
>   4 files changed, 3 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/pci/pci.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.c
> +++ linux-pm/drivers/pci/pci.c
> @@ -1840,6 +1840,7 @@ int pci_finish_runtime_suspend(struct pc
>
>   	return error;
>   }
> +EXPORT_SYMBOL_GPL(pci_finish_runtime_suspend);
>
>   /**
>    * pci_dev_run_wake - Check if device can generate run-time wake-up events.
> Index: linux-pm/drivers/pci/pci.h
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.h
> +++ linux-pm/drivers/pci/pci.h
> @@ -64,7 +64,6 @@ extern int pci_set_platform_pm(struct pc
>   extern void pci_update_current_state(struct pci_dev *dev, pci_power_t state);
>   extern void pci_power_up(struct pci_dev *dev);
>   extern void pci_disable_enabled_device(struct pci_dev *dev);
> -extern int pci_finish_runtime_suspend(struct pci_dev *dev);
>   extern int __pci_pme_wakeup(struct pci_dev *dev, void *ign);
>   extern void pci_wakeup_bus(struct pci_bus *bus);
>   extern void pci_config_pm_runtime_get(struct pci_dev *dev);
> Index: linux-pm/include/linux/pci.h
> ===================================================================
> --- linux-pm.orig/include/linux/pci.h
> +++ linux-pm/include/linux/pci.h
> @@ -936,6 +936,7 @@ int pci_back_from_sleep(struct pci_dev *
>   bool pci_dev_run_wake(struct pci_dev *dev);
>   bool pci_check_pme_status(struct pci_dev *dev);
>   void pci_pme_wakeup_bus(struct pci_bus *bus);
> +int pci_finish_runtime_suspend(struct pci_dev *dev);
>
>   static inline int pci_enable_wake(struct pci_dev *dev, pci_power_t state,
>   				  bool enable)
> Index: linux-pm/drivers/net/ethernet/intel/e1000e/netdev.c
> ===================================================================
> --- linux-pm.orig/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ linux-pm/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -5696,6 +5696,7 @@ static int e1000_runtime_suspend(struct
>   		bool wake;
>
>   		__e1000_shutdown(pdev,&wake, true);
> +		pci_finish_runtime_suspend(pdev);
>   	}
>
>   	return 0;
>
>
>