[PATCH 1/2] PCI/ACPI: correct error message for ASPM disabling

[PATCH 1/2] PCI/ACPI: correct error message for ASPM disabling

[Sinan Kaya]

If _OSC execution fails today for platforms without an _OSC
entry, code is printing a misleading message saying disabling
ASPM as follows:

acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM

We need to ensure that platform supports ASPM to begin with.

Signed-off-by: Sinan Kaya <okaya@kernel.org>
Reported-by: Michael Kelley <mikelley@microsoft.com>
---
 drivers/acpi/pci_root.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 7433035..9d738e2 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -455,8 +455,13 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 	decode_osc_support(root, "OS supports", support);
 	status = acpi_pci_osc_support(root, support);
 	if (ACPI_FAILURE(status)) {
-		dev_info(&device->dev, "_OSC failed (%s); disabling ASPM\n",
-			 acpi_format_exception(status));
+		char *aspm_msg = "";
+
+		if (pcie_aspm_support_enabled())
+			aspm_msg = "; disabling ASPM";
+
+		dev_info(&device->dev, "_OSC failed (%s) %s\n",
+				 acpi_format_exception(status), aspm_msg);
 		*no_aspm = 1;
 		return;
 	}
-- 
2.7.4

[PATCH 2/2] PCI/ACPI: allow _OSC presence to be optional for PCI

[Sinan Kaya]

ACPI Spec 6.0 Section 6.2.11.3 OSC Implementation Example for PCI
Host Bridge Devices:

For a host bridge device that originates a PCI Express hierarchy,
the _OSC interface defined in this section is required.

For a host bridge device that originates a PCI/PCI-X bus hierarchy,
inclusion of an _OSC object is optional.

Allow PCI host bridges to bail out silently if _OSC is not found.

Signed-off-by: Sinan Kaya <okaya@kernel.org>
Reported-by: Michael Kelley <mikelley@microsoft.com>
---
 drivers/acpi/pci_root.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 9d738e2..c94ed01 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -421,7 +421,8 @@ acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 req)
 }
 EXPORT_SYMBOL(acpi_pci_osc_control_set);
 
-static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
+static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
+				 bool is_pcie)
 {
 	u32 support, control, requested;
 	acpi_status status;
@@ -460,9 +461,14 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 		if (pcie_aspm_support_enabled())
 			aspm_msg = "; disabling ASPM";
 
-		dev_info(&device->dev, "_OSC failed (%s) %s\n",
-				 acpi_format_exception(status), aspm_msg);
 		*no_aspm = 1;
+
+		/* _OSC is optional for PCI host bridges */
+		if ((status == AE_NOT_FOUND) && !is_pcie)
+			return;
+
+		dev_info(&device->dev, "_OSC failed (%s) %s\n",
+			 acpi_format_exception(status), aspm_msg);
 		return;
 	}
 
@@ -538,6 +544,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
 	acpi_handle handle = device->handle;
 	int no_aspm = 0;
 	bool hotadd = system_state == SYSTEM_RUNNING;
+	bool is_pcie;
 
 	root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
 	if (!root)
@@ -595,7 +602,8 @@ static int acpi_pci_root_add(struct acpi_device *device,
 
 	root->mcfg_addr = acpi_pci_root_get_mcfg_addr(handle);
 
-	negotiate_os_control(root, &no_aspm);
+	is_pcie = strcmp(acpi_device_hid(device), "PNP0A08") == 0;
+	negotiate_os_control(root, &no_aspm, is_pcie);
 
 	/*
 	 * TBD: Need PCI interface for enumeration/configuration of roots.
-- 
2.7.4

Re: [PATCH 1/2] PCI/ACPI: correct error message for ASPM disabling

[Joe Perches]

On Thu, 2018-08-09 at 18:46 +0000, Sinan Kaya wrote:
> If _OSC execution fails today for platforms without an _OSC
> entry, code is printing a misleading message saying disabling
> ASPM as follows:
> 
> acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM
> 
> We need to ensure that platform supports ASPM to begin with.
> 
> Signed-off-by: Sinan Kaya <okaya@kernel.org>
> Reported-by: Michael Kelley <mikelley@microsoft.com>
> ---
>  drivers/acpi/pci_root.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
[]
> @@ -455,8 +455,13 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
>  	decode_osc_support(root, "OS supports", support);
>  	status = acpi_pci_osc_support(root, support);
>  	if (ACPI_FAILURE(status)) {
> -		dev_info(&device->dev, "_OSC failed (%s); disabling ASPM\n",
> -			 acpi_format_exception(status));
> +		char *aspm_msg = "";
> +
> +		if (pcie_aspm_support_enabled())
> +			aspm_msg = "; disabling ASPM";
> +
> +		dev_info(&device->dev, "_OSC failed (%s) %s\n",
> +				 acpi_format_exception(status), aspm_msg);

I think this would read better not using a temporary and
using a ternary instead.

		dev_info(&device->dev, "_OSC failed (%s)%s\n",
			 acpi_format_exception(status),
			 pcie_aspm_support_enabled() ? "; disabling ASPM" : "");

>  		*no_aspm = 1;
>  		return;
>  	}

Re: [PATCH 1/2] PCI/ACPI: correct error message for ASPM disabling

[Sinan Kaya]

On 8/9/2018 8:27 PM, Joe Perches wrote:
> I think this would read better not using a temporary and
> using a ternary instead.

Makes sense.