Re: [PATCH update] PCI / ACPI: PCI delay optimization from ACPI

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Friday, March 20, 2015 02:14:38 PM Aaron Lu wrote:
> I wonder if there is any more comments about this patch?

I don't have any, but I'd like to know the Bjorn's opinion too.


> On 03/10/2015 02:48 PM, Aaron Lu wrote:
> > An ECN meant to specify possible delay optimizations is available on
> > the PCI website:
> > https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
> > where it has defined two functions for an UUID specified _DSM:
> > Function 8: If system firmware assumes the responsibility of post
> > Conventional Reset delay (and informs the Operating System via this DSM
> > function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI
> > S4 or S3 states), the Operating System may assume sufficient time has
> > elapsed since the end of reset, and devices within the PCI subsystem are
> > ready for Configuration Access.
> > If the system firmware supports runtime power gating on any of the
> > device within PCI subsystem covered by this DSM function, the system
> > firmware is responsible for covering the necessary post power-on reset
> > delay.
> > 
> > Function 9: Specify various smaller delay values than required by the
> > SPEC for individual PCI devices like shorter delay values after
> > conventional reset, D3hot to D0 transition, functional level reset, etc.
> > 
> > This patche adds support for function 8 and part of function 9. For
> > function 8, the patch will check if the required _DSM function satisfies
> > the requirement and then set the per PCI device's d3cold_delay variable
> > to zero. For function 9, the values affecting delays after conventional
> > reset and D3hot->D0 are examined and the per PCI device's d3cold_delay
> > and d3_delay are updated if the _DSM's return value is smaller than what
> > the SPEC requires.
> > 
> > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
> > ---
> >  drivers/pci/pci-acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 61 insertions(+)
> > 
> > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> > index 489063987325..468c0733838e 100644
> > --- a/drivers/pci/pci-acpi.c
> > +++ b/drivers/pci/pci-acpi.c
> > @@ -558,6 +558,64 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
> >  				      check_children);
> >  }
> >  
> > +/**
> > + * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
> > + * @pdev: the PCI device whose delay is to be updated
> > + * @adev: the companion ACPI device of this PCI device
> > + *
> > + * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
> > + * control method of either its own or its parent bridge.
> > + *
> > + * The UUID of the _DSM control method, together with other information like
> > + * which delay values can be optimized, etc. is defined in a ECN available on
> > + * PCIsig.com titled as: ACPI additions for FW latency optimizations.
> > + * Function 9 of the ACPI _DSM control method, if available for a specific PCI
> > + * device, provides various possible delay values that are less than what the
> > + * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
> > + * can be added later.
> > + * Function 8 of the ACPI _DSM control method, if available for a specific PCI
> > + * bridge, means all its children devices do not need the reset delay when
> > + * leaving from D3cold state.
> > + */
> > +static void pci_acpi_delay_optimize(struct pci_dev *pdev, struct acpi_device *adev)
> > +{
> > +	const u8 uuid[] = {
> > +		0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
> > +		0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
> > +	};
> > +	int revision = 3, function = 9, value;
> > +	acpi_handle handle = adev->handle;
> > +	union acpi_object *obj, *elements;
> > +
> > +	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
> > +	if (obj) {
> > +		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
> > +			elements = obj->package.elements;
> > +			if (elements[3].type == ACPI_TYPE_INTEGER) {
> > +				value = (int)elements[3].integer.value / 1000;
> > +				if (value < PCI_PM_D3_WAIT)
> > +					pdev->d3_delay = value;
> > +			}
> > +			if (elements[0].type == ACPI_TYPE_INTEGER) {
> > +				value = (int)elements[0].integer.value / 1000;
> > +				if (value < PCI_PM_D3COLD_WAIT)
> > +					pdev->d3cold_delay = value;
> > +			}
> > +		}
> > +		kfree(obj);
> > +	}
> > +
> > +	function = 8;
> > +	handle = ACPI_HANDLE(pdev->bus->bridge);
> > +	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
> > +	if (!obj)
> > +		return;
> > +
> > +	if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
> > +		pdev->d3cold_delay = 0;
> > +	kfree(obj);
> > +}
> > +
> >  static void pci_acpi_setup(struct device *dev)
> >  {
> >  	struct pci_dev *pci_dev = to_pci_dev(dev);
> > @@ -566,6 +624,9 @@ static void pci_acpi_setup(struct device *dev)
> >  	if (!adev)
> >  		return;
> >  
> > +	if (pci_dev->pm_cap)
> > +		pci_acpi_delay_optimize(pci_dev, adev);
> > +
> >  	pci_acpi_add_pm_notifier(adev, pci_dev);
> >  	if (!adev->wakeup.flags.valid)
> >  		return;
> > 
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux IBM ACPI]     [Linux Power Management]     [Linux Kernel]     [Linux Laptop]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Device Mapper]     [Linux Resources]

  Powered by Linux