Re: [PATCH v2 2/2] PCI/ACPI: Improve _OSC control request granularity

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Oct 25, 2018 at 11:01:32AM -0500, Aaron Sierra wrote:
> This patch reorganizes negotiate_os_control() to be less ASPM-centric in
> order to:
> 
>     1. allow other features (notably AER) to work without enabling ASPM
>     2. better isolate feature-specific tests for readability/maintenance

I really like this idea; thanks for working it up!

> Each feature (ASPM, PCIe hotplug, SHPC hotplug, and AER) now has its own
> inline function for setting its _OSC control requests.
> 
> Part of making this function more generic, required eliminating a test
> for overall success/failure that previously caused two different types
> of messages to be printed. Now, printed messages are streamlined to
> always show requested _OSC control versus what was granted.
> 
> Previous output (success):
> 
>   acpi PNP0A08:00: _OSC: OS now controls [PME AER PCIeCapability LTR]
> 
> Previous output (failure):
> 
>   acpi PNP0A08:00: _OSC: OS requested [PME AER PCIeCapability LTR]
>   acpi PNP0A08:00: _OSC: platform willing to grant []
> 
> Now:
> 
>   acpi PNP0A08:00: _OSC: OS requested [PME AER PCIeCapability LTR]
>   acpi PNP0A08:00: _OSC: platform granted [PME AER PCIeCapability LTR]
> 
> Signed-off-by: Aaron Sierra <asierra@xes-inc.com>
> ---
>  drivers/acpi/pci_root.c | 118 ++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 85 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index eb9f14e..9685aba 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -53,9 +53,10 @@ static int acpi_pci_root_scan_dependent(struct acpi_device *adev)
>  }
>  
>  #define ACPI_PCIE_REQ_SUPPORT (OSC_PCI_EXT_CONFIG_SUPPORT \
> -				| OSC_PCI_ASPM_SUPPORT \
> -				| OSC_PCI_CLOCK_PM_SUPPORT \
>  				| OSC_PCI_MSI_SUPPORT)
> +#define ACPI_PCIE_ASPM_SUPPORT (ACPI_PCIE_REQ_SUPPORT \
> +				| OSC_PCI_ASPM_SUPPORT \
> +				| OSC_PCI_CLOCK_PM_SUPPORT)
>  
>  static const struct acpi_device_id root_device_ids[] = {
>  	{"PNP0A03", 0},
> @@ -421,6 +422,72 @@ acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 req)
>  }
>  EXPORT_SYMBOL(acpi_pci_osc_control_set);
>  
> +static inline bool __osc_have_support(u32 support, u32 required)
> +{
> +	return ((support & required) == required);
> +}

I'm not really a fan of function names with leading underscores, except
maybe for "raw" things that don't acquire locks.

> +static inline int __osc_set_aspm_control(struct acpi_pci_root *root,
> +					 u32 support, u32 *control)
> +{
> +	if (!IS_ENABLED(CONFIG_PCIEASPM) ||
> +	    !__osc_have_support(support, ACPI_PCIE_ASPM_SUPPORT))
> +		return -ENODEV;
> +
> +	*control |= OSC_PCI_EXPRESS_CAPABILITY_CONTROL |
> +		    OSC_PCI_EXPRESS_LTR_CONTROL |
> +		    OSC_PCI_EXPRESS_PME_CONTROL;

I think this would be more readable if we could avoid the double
negatives, e.g.,

  if (IS_ENABLED(CONFIG_PCIEASPM) &&
      __osc_have_support(support, ACPI_PCIE_ASPM_SUPPORT)) {
          *control |= OSC_PCI_EXPRESS_CAPABILITY_CONTROL |
                      OSC_PCI_EXPRESS_LTR_CONTROL |
                      OSC_PCI_EXPRESS_PME_CONTROL;
          return 0;
  }

  return -ENODEV;

Since the caller ignores the return values anyway, I wonder if this
could also work by *returning* the new mask bits instead of using
"control" as a reference parameter, e.g.,

  if (IS_ENABLED(...))
    return OSC_PCI_EXPRESS_CAPABILITY_CONTROL |
           OSC_PCI_EXPRESS_LTR_CONTROL |
           OSC_PCI_EXPRESS_PME_CONTROL;

  return 0;

Then the calls would look like:

  control |= __osc_set_pciehp_control(root, support);
  control |= __osc_set_shpchp_control(root, support);
  ...

> +	return 0;
> +}
> +
> +static inline bool __osc_have_aspm_control(u32 control)
> +{
> +	u32 required = OSC_PCI_EXPRESS_CAPABILITY_CONTROL |
> +		       OSC_PCI_EXPRESS_LTR_CONTROL |
> +		       OSC_PCI_EXPRESS_PME_CONTROL;
> +
> +	return __osc_have_support(control, required);
> +}
> +
> +static inline void __osc_set_pciehp_control(struct acpi_pci_root *root,
> +					    u32 support, u32 *control)
> +{
> +	if (!IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE) ||
> +	    !__osc_have_support(support, ACPI_PCIE_REQ_SUPPORT))
> +		return;
> +
> +	*control |= OSC_PCI_EXPRESS_CAPABILITY_CONTROL |
> +		    OSC_PCI_EXPRESS_NATIVE_HP_CONTROL;
> +}
> +
> +static inline void __osc_set_shpchp_control(struct acpi_pci_root *root,
> +					    u32 support, u32 *control)
> +{
> +	if (!IS_ENABLED(CONFIG_HOTPLUG_PCI_SHPC) ||
> +	    !__osc_have_support(support, ACPI_PCIE_REQ_SUPPORT))
> +		return;
> +
> +	*control |= OSC_PCI_EXPRESS_CAPABILITY_CONTROL |
> +		    OSC_PCI_SHPC_NATIVE_HP_CONTROL;
> +}
> +
> +static inline void __osc_set_aer_control(struct acpi_pci_root *root,
> +					 u32 support, u32 *control)
> +{
> +	if (!pci_aer_available() ||
> +	    !__osc_have_support(support, ACPI_PCIE_REQ_SUPPORT))
> +		return;
> +
> +	if (aer_acpi_firmware_first()) {
> +		dev_info(&root->device->dev, "PCIe AER handled by firmware\n");
> +		return;
> +	}
> +
> +	*control |= OSC_PCI_EXPRESS_CAPABILITY_CONTROL |
> +		    OSC_PCI_EXPRESS_AER_CONTROL;
> +}
> +
>  static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
>  				 bool is_pcie)
>  {
> @@ -474,37 +541,25 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
>  		return;
>  	}
>  
> -	if ((support & ACPI_PCIE_REQ_SUPPORT) != ACPI_PCIE_REQ_SUPPORT) {
> -		decode_osc_support(root, "not requesting OS control; OS requires",
> -				   ACPI_PCIE_REQ_SUPPORT);
> -		return;
> -	}
> -
> -	control = OSC_PCI_EXPRESS_CAPABILITY_CONTROL
> -		| OSC_PCI_EXPRESS_PME_CONTROL;
> -
> -	if (IS_ENABLED(CONFIG_PCIEASPM))
> -		control |= OSC_PCI_EXPRESS_LTR_CONTROL;
> -
> -	if (IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE))
> -		control |= OSC_PCI_EXPRESS_NATIVE_HP_CONTROL;
> +	control = 0;
> +	if (__osc_set_aspm_control(root, support, &control))
> +		*no_aspm = 1;
>  
> -	if (IS_ENABLED(CONFIG_HOTPLUG_PCI_SHPC))
> -		control |= OSC_PCI_SHPC_NATIVE_HP_CONTROL;
> +	__osc_set_pciehp_control(root, support, &control);
> +	__osc_set_shpchp_control(root, support, &control);
> +	__osc_set_aer_control(root, support, &control);
>  
> -	if (pci_aer_available()) {
> -		if (aer_acpi_firmware_first())
> -			dev_info(&device->dev,
> -				 "PCIe AER handled by firmware\n");
> -		else
> -			control |= OSC_PCI_EXPRESS_AER_CONTROL;
> +	if (!control) {
> +		dev_info(&device->dev, "_OSC: not requesting OS control\n");
> +		return;
>  	}
>  
>  	requested = control;
> -	status = acpi_pci_osc_control_set(handle, &control,
> -					  OSC_PCI_EXPRESS_CAPABILITY_CONTROL);
> -	if (ACPI_SUCCESS(status)) {
> -		decode_osc_control(root, "OS now controls", control);
> +	acpi_pci_osc_control_set(handle, &control, 0);
> +	decode_osc_control(root, "OS requested", requested);
> +	decode_osc_control(root, "platform granted", control);
> +
> +	if (__osc_have_aspm_control(control)) {
>  		if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
>  			/*
>  			 * We have ASPM control, but the FADT indicates that
> @@ -514,11 +569,8 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
>  			dev_info(&device->dev, "FADT indicates ASPM is unsupported, using BIOS configuration\n");
>  			*no_aspm = 1;
>  		}
> -	} else {
> -		decode_osc_control(root, "OS requested", requested);
> -		decode_osc_control(root, "platform willing to grant", control);
> -		dev_info(&device->dev, "_OSC failed (%s); disabling ASPM\n",
> -			acpi_format_exception(status));
> +	} else if (!*no_aspm) {
> +		dev_info(&device->dev, "_OSC failed; disabling ASPM\n");
>  
>  		/*
>  		 * We want to disable ASPM here, but aspm_disabled
> -- 
> 2.7.4
>