Re: [RFC PATCH] PCIe: Add PCIe runtime D3cold support

Yan, Zheng
2012-04-16T02:23:10Z

On 04/14/2012 03:41 AM, Rafael J. Wysocki wrote:
> Hi,
>
> On Friday, April 13, 2012, Yan, Zheng wrote:
>> Hi all,
>>
>> This patch adds PCIe runtime D3cold support, namely cut power supply for functions
>> beneath a PCIe port when they all have entered D3. A device in D3cold can only
>> generate wake event through the WAKE# pin. Because we can not access to a device's
>> configure space while it's in D3cold, pme_poll is disabled for devices in D3cold.
>>
>> Any comment will be appreciated.
>>
>> Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
>> ---
>> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
>> index 0f150f2..e210e8cb 100644
>> --- a/drivers/pci/pci-acpi.c
>> +++ b/drivers/pci/pci-acpi.c
>> @@ -224,7 +224,7 @@ static int acpi_pci_set_power_state(struct pci_dev *dev, pci_power_t state)
>> [PCI_D1] = ACPI_STATE_D1,
>> [PCI_D2] = ACPI_STATE_D2,
>> [PCI_D3hot] = ACPI_STATE_D3,
>> - [PCI_D3cold] = ACPI_STATE_D3
>> + [PCI_D3cold] = ACPI_STATE_D3_COLD
>> };
>> int error = -EINVAL;
>>
>
> Please don't use that ACPI_STATE_D3_COLD thing, it's not defined correctly.
>
> We should define ACPI_STATE_D3_COLD == ACPI_STATE_D3 and add ACPI_STATE_D3_HOT
> instead. I'll prepare a patch for that over the weekend if no one has done
> that already.
>
>> @@ -296,7 +296,8 @@ static void acpi_pci_propagate_run_wake(struct pci_bus *bus, bool enable)
>>
>> static int acpi_pci_run_wake(struct pci_dev *dev, bool enable)
>> {
>> - if (dev->pme_interrupt)
>> + /* PME interrupt isn't available in the D3cold case */
>> + if (dev->pme_interrupt && !dev->runtime_d3cold)
>
> This whole thing is wrong. First off, I don't think that the runtime_d3cold
> flag makes any sense. We already cover that in dev->pme_support.
>
> Second, pme_interrupt means that the _root_ _port_, not the device itself will
> trigger an interrupt whenever the device sends the PME message to it (which
> very well may happen for a device in D3_cold woken up by an external signal).
>
The reason I introduced the runtime_d3cold flag is I can't make the PME interrupt
work in the D3cold case in our test platform. Document for our test platform says
A device in D3cold can only generate wake event through the WAKE# pin.

>> return 0;
>>
>> if (!acpi_pm_device_run_wake(&dev->dev, enable))
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index 8156744..bc16869 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -731,8 +731,8 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
>> int error;
>>
>
> Guys, please. Never, _ever_, touch pci_set_power_state() without discussing
> your ideas with someone who knows how it works and _why_ it works this way.
>
> The problem here is that you can't program a PCI device into D3_cold, so it
> doesn't even make sense to have a helper for that.
>
>> /* bound the state we're entering */
>> - if (state > PCI_D3hot)
>> - state = PCI_D3hot;
>> + if (state > PCI_D3cold)
>> + state = PCI_D3cold;
>> else if (state < PCI_D0)
>> state = PCI_D0;
>> else if ((state == PCI_D1 || state == PCI_D2) && pci_no_d1d2(dev))
>> @@ -750,7 +750,8 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
>> if (state == PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
>> return 0;
>>
>> - error = pci_raw_set_power_state(dev, state);
>> + error = pci_raw_set_power_state(dev, state > PCI_D3hot ?
>> + PCI_D3hot : state);
>>
>> if (!__pci_complete_power_transition(dev, state))
>> error = 0;
>> @@ -1482,6 +1483,17 @@ bool pci_pme_capable(struct pci_dev *dev, pci_power_t state)
>> return !!(dev->pme_support & (1 << state));
>> }
>>
>> +static void pci_pme_poll_wakeup(struct pci_dev *dev)
>> +{
>> + struct pci_dev *bridge = dev->bus->self;
>> +
>> + /* don't poll the pme bit if parent is in low power state */
>> + if (bridge && bridge->current_state != PCI_D0)
>> + return;
>> +
>> + pci_pme_wakeup(dev, NULL);
>> +}
>
> This one actually makes some sense, although it might be better to put the
> test into pci_pme_wakeup() itself.

put it into pci_pme_wakeup will break ACPI wakeup, because ACPI wakeup also
uses pci_pme_wakeup. When a device exits from D3cold by asserting the WAKE#
signal, device power is restored automatically by ACPI, then pci_pme_wakeup
is called to check device's PME bit. pci_dev->current_state is PCI_D3hot
during the checking.

>
>> +
>> static void pci_pme_list_scan(struct work_struct *work)
>> {
>> struct pci_pme_device *pme_dev, *n;
>> @@ -1490,7 +1502,7 @@ static void pci_pme_list_scan(struct work_struct *work)
>> if (!list_empty(&pci_pme_list)) {
>> list_for_each_entry_safe(pme_dev, n, &pci_pme_list, list) {
>> if (pme_dev->dev->pme_poll) {
>> - pci_pme_wakeup(pme_dev->dev, NULL);
>> + pci_pme_poll_wakeup(pme_dev->dev);
>> } else {
>> list_del(&pme_dev->list);
>> kfree(pme_dev);
>> @@ -1608,6 +1620,10 @@ int __pci_enable_wake(struct pci_dev *dev, pci_power_t state,
>> if (enable) {
>> int error;
>>
>> + if (runtime && state >= PCI_D3cold)
>> + dev->runtime_d3cold = true;
>> + else
>> + dev->runtime_d3cold = false;
>> if (pci_pme_capable(dev, state))
>> pci_pme_active(dev, true);
>> else
>> diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
>> index e0610bd..d66b7e9 100644
>> --- a/drivers/pci/pcie/portdrv_pci.c
>> +++ b/drivers/pci/pcie/portdrv_pci.c
>> @@ -11,11 +11,13 @@
>> #include <linux/kernel.h>
>> #include <linux/errno.h>
>> #include <linux/pm.h>
>> +#include <linux/pm_runtime.h>
>> #include <linux/init.h>
>> #include <linux/pcieport_if.h>
>> #include <linux/aer.h>
>> #include <linux/dmi.h>
>> #include <linux/pci-aspm.h>
>> +#include <linux/delay.h>
>>
>> #include "portdrv.h"
>> #include "aer/aerdrv.h"
>> @@ -99,6 +101,25 @@ static int pcie_port_resume_noirq(struct device *dev)
>> return 0;
>> }
>>
>> +static int pcie_port_runtime_suspend(struct device *dev)
>> +{
>> + struct pci_dev *pdev = to_pci_dev(dev);
>> +
>> + pci_save_state(pdev);
>
> Are you sure this is sufficient?

What else should I do?

>
>> + return 0;
>> +}
>> +
>> +static int pcie_port_runtime_resume(struct device *dev)
>> +{
>> + struct pci_dev *pdev = to_pci_dev(dev);
>> +
>> + pci_restore_state(pdev);
>> + if (pdev->runtime_d3cold)
>> + msleep(100);
>
> What's _that_ supposed to do?

Bad thing happens if device is accessed immediately after restoring power.
Document for our test platform states 100ms PERST delay is required.

>
>> +
>> + return 0;
>> +}
>> +
>> static const struct dev_pm_ops pcie_portdrv_pm_ops = {
>> .suspend = pcie_port_device_suspend,
>> .resume = pcie_port_device_resume,
>> @@ -107,6 +128,8 @@ static const struct dev_pm_ops pcie_portdrv_pm_ops = {
>> .poweroff = pcie_port_device_suspend,
>> .restore = pcie_port_device_resume,
>> .resume_noirq = pcie_port_resume_noirq,
>> + .runtime_suspend = pcie_port_runtime_suspend,
>> + .runtime_resume = pcie_port_runtime_resume,
>> };
>>
>> #define PCIE_PORTDRV_PM_OPS (&pcie_portdrv_pm_ops)
>> @@ -144,12 +167,14 @@ static int __devinit pcie_portdrv_probe(struct pci_dev *dev,
>> return status;
>>
>> pci_save_state(dev);
>> + pm_runtime_put_noidle(&dev->dev);
>
> What's the purpose of this?
>
>> return 0;
>> }
>>
>> static void pcie_portdrv_remove(struct pci_dev *dev)
>> {
>> + pm_runtime_get_noresume(&dev->dev);
>> pcie_port_device_remove(dev);
>> pci_disable_device(dev);
>> }
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index e444f5b..b41d9a1 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -281,6 +281,7 @@ struct pci_dev {
>> unsigned int no_d1d2:1; /* Only allow D0 and D3 */
>> unsigned int mmio_always_on:1; /* disallow turning off io/mem
>> decoding during bar sizing */
>> + unsigned int runtime_d3cold:1;
>> unsigned int wakeup_prepared:1;
>> unsigned int d3_delay; /* D3->D0 transition time in ms */
>
> OK
>
> So now please tell me what exactly you want to achieve and why you want to do
> that in the first place.
>
> Thanks,
> Rafael