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

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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@xxxxxxxxx>
> ---
> 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).

>  		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.

> +
>  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?

> +	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?

> +
> +	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
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