[v2,1/2] PCI/ACPI: Use CXL _OSC instead of PCIe _OSC

Commit Message

Verma, Vishal L March 26, 2022, 12:24 a.m. UTC

From: Dan Williams <[e-mail]>

OB In preparation for negotiating OS control of CXL _OSC features, do the
minimal enabling to use CXL _OSC to handle the base PCIe feature
negotiation. Recall that CXL _OSC is a super-set of PCIe _OSC and the
CXL 2.0 specification mandates: "If a CXL Host Bridge device exposes CXL
_OSC, CXL aware OSPM shall evaluate CXL _OSC and not evaluate PCIe
_OSC."

Rather than pass a boolean flag alongside @root to all the helper
functions that need to consider PCIe specifics, add is_pcie() and
is_cxl() helper functions to check the flavor of @root. This also
allows for dynamic fallback to PCIe _OSC in cases where an attempt to
use CXL _OXC fails. This can happen on CXL 1.1 platforms that publish
ACPI0016 devices to indicate CXL host bridges, but do not publish the
optional CXL _OSC method. CXL _OSC is mandatory for CXL 2.0 hosts.

Cc: Bjorn Helgaas <[e-mail]>
Cc: "Rafael J. Wysocki" <[e-mail]>
Cc: Robert Moore <[e-mail]>
Reviewed-by: Jonathan Cameron <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>
Signed-off-by: Vishal Verma <[e-mail]>
---
 include/linux/acpi.h    |  4 +++
 include/acpi/acpi_bus.h |  6 ++++
 drivers/acpi/pci_root.c | 74 ++++++++++++++++++++++++++++++++---------
 3 files changed, 69 insertions(+), 15 deletions(-)

Comments

Davidlohr Bueso March 28, 2022, 6:35 p.m. UTC | #1

On Fri, 25 Mar 2022, Vishal Verma wrote:

>+static bool is_pcie(struct acpi_pci_root *root)
>+{
>+	if (root->bridge_type == ACPI_BRIDGE_TYPE_PCIE)
>+		return true;
>+	return false;
>+}
>
>-static acpi_status acpi_pci_run_osc(acpi_handle handle,
>+static bool is_cxl(struct acpi_pci_root *root)
>+{
>+	if (root->bridge_type == ACPI_BRIDGE_TYPE_CXL)
>+		return true;
>+	return false;
>+}

return root->bridge_type == TYPE

Verma, Vishal L March 28, 2022, 7:04 p.m. UTC | #2

On Mon, 2022-03-28 at 11:35 -0700, Davidlohr Bueso wrote:
> On Fri, 25 Mar 2022, Vishal Verma wrote:
> 
> > +static bool is_pcie(struct acpi_pci_root *root)
> > +{
> > +       if (root->bridge_type == ACPI_BRIDGE_TYPE_PCIE)
> > +               return true;
> > +       return false;
> > +}
> > 
> > -static acpi_status acpi_pci_run_osc(acpi_handle handle,
> > +static bool is_cxl(struct acpi_pci_root *root)
> > +{
> > +       if (root->bridge_type == ACPI_BRIDGE_TYPE_CXL)
> > +               return true;
> > +       return false;
> > +}
> 
> return root->bridge_type == TYPE

Oh, yes, of course - I'll fix up!

Patch

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 6274758648e3..f41e8b00a839 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -550,6 +550,10 @@  struct acpi_osc_context {
 
 acpi_status acpi_run_osc(acpi_handle handle, struct acpi_osc_context *context);
 
+/* Number of _OSC capability DWORDS depends on bridge type */
+#define OSC_PCI_CAPABILITY_DWORDS		3
+#define OSC_CXL_CAPABILITY_DWORDS		5
+
 /* Indexes into _OSC Capabilities Buffer (DWORDs 2 & 3 are device-specific) */
 #define OSC_QUERY_DWORD				0	/* DWORD 1 */
 #define OSC_SUPPORT_DWORD			1	/* DWORD 2 */
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index ca88c4706f2b..9413d2389711 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -581,10 +581,16 @@  int unregister_acpi_bus_type(struct acpi_bus_type *);
 int acpi_bind_one(struct device *dev, struct acpi_device *adev);
 int acpi_unbind_one(struct device *dev);
 
+enum acpi_bridge_type {
+	ACPI_BRIDGE_TYPE_PCIE = 1,
+	ACPI_BRIDGE_TYPE_CXL,
+};
+
 struct acpi_pci_root {
 	struct acpi_device * device;
 	struct pci_bus *bus;
 	u16 segment;
+	int bridge_type;
 	struct resource secondary;	/* downstream bus range */
 
 	u32 osc_support_set;	/* _OSC state of support bits */
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index b76db99cced3..170fe8c6fa5e 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -170,20 +170,49 @@  static void decode_osc_control(struct acpi_pci_root *root, char *msg, u32 word)
 			ARRAY_SIZE(pci_osc_control_bit));
 }
 
-static u8 pci_osc_uuid_str[] = "33DB4D5B-1FF7-401C-9657-7441C03DD766";
+static bool is_pcie(struct acpi_pci_root *root)
+{
+	if (root->bridge_type == ACPI_BRIDGE_TYPE_PCIE)
+		return true;
+	return false;
+}
 
-static acpi_status acpi_pci_run_osc(acpi_handle handle,
+static bool is_cxl(struct acpi_pci_root *root)
+{
+	if (root->bridge_type == ACPI_BRIDGE_TYPE_CXL)
+		return true;
+	return false;
+}
+
+static u8 pci_osc_uuid_str[] = "33DB4D5B-1FF7-401C-9657-7441C03DD766";
+static u8 cxl_osc_uuid_str[] = "68F2D50B-C469-4d8A-BD3D-941A103FD3FC";
+
+static char *to_uuid(struct acpi_pci_root *root)
+{
+	if (is_cxl(root))
+		return cxl_osc_uuid_str;
+	return pci_osc_uuid_str;
+}
+
+static int cap_length(struct acpi_pci_root *root)
+{
+	if (is_cxl(root))
+		return sizeof(u32) * OSC_CXL_CAPABILITY_DWORDS;
+	return sizeof(u32) * OSC_PCI_CAPABILITY_DWORDS;
+}
+
+static acpi_status acpi_pci_run_osc(struct acpi_pci_root *root,
 				    const u32 *capbuf, u32 *retval)
 {
 	struct acpi_osc_context context = {
-		.uuid_str = pci_osc_uuid_str,
+		.uuid_str = to_uuid(root),
 		.rev = 1,
-		.cap.length = 12,
+		.cap.length = cap_length(root),
 		.cap.pointer = (void *)capbuf,
 	};
 	acpi_status status;
 
-	status = acpi_run_osc(handle, &context);
+	status = acpi_run_osc(root->device->handle, &context);
 	if (ACPI_SUCCESS(status)) {
 		*retval = *((u32 *)(context.ret.pointer + 8));
 		kfree(context.ret.pointer);
@@ -196,7 +225,7 @@  static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
 					u32 *control)
 {
 	acpi_status status;
-	u32 result, capbuf[3];
+	u32 result, capbuf[OSC_CXL_CAPABILITY_DWORDS];
 
 	support |= root->osc_support_set;
 
@@ -204,10 +233,18 @@  static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
 	capbuf[OSC_SUPPORT_DWORD] = support;
 	capbuf[OSC_CONTROL_DWORD] = *control | root->osc_control_set;
 
-	status = acpi_pci_run_osc(root->device->handle, capbuf, &result);
+retry:
+	status = acpi_pci_run_osc(root, capbuf, &result);
 	if (ACPI_SUCCESS(status)) {
 		root->osc_support_set = support;
 		*control = result;
+	} else if (is_cxl(root)) {
+		/*
+		 * CXL _OSC is optional on CXL 1.1 hosts. Fall back to PCIe _OSC
+		 * upon any failure using CXL _OSC.
+		 */
+		root->bridge_type = ACPI_BRIDGE_TYPE_PCIE;
+		goto retry;
 	}
 	return status;
 }
@@ -338,7 +375,7 @@  static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 s
 	u32 req = OSC_PCI_EXPRESS_CAPABILITY_CONTROL;
 	struct acpi_pci_root *root;
 	acpi_status status;
-	u32 ctrl, capbuf[3];
+	u32 ctrl, capbuf[OSC_CXL_CAPABILITY_DWORDS];
 
 	if (!mask)
 		return AE_BAD_PARAMETER;
@@ -375,7 +412,7 @@  static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 s
 	capbuf[OSC_QUERY_DWORD] = 0;
 	capbuf[OSC_SUPPORT_DWORD] = root->osc_support_set;
 	capbuf[OSC_CONTROL_DWORD] = ctrl;
-	status = acpi_pci_run_osc(handle, capbuf, mask);
+	status = acpi_pci_run_osc(root, capbuf, mask);
 	if (ACPI_FAILURE(status))
 		return status;
 
@@ -454,8 +491,7 @@  static bool os_control_query_checks(struct acpi_pci_root *root, u32 support)
 	return true;
 }
 
-static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
-				 bool is_pcie)
+static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 {
 	u32 support, control = 0, requested = 0;
 	acpi_status status;
@@ -506,7 +542,7 @@  static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
 		*no_aspm = 1;
 
 		/* _OSC is optional for PCI host bridges */
-		if ((status == AE_NOT_FOUND) && !is_pcie)
+		if (status == AE_NOT_FOUND && !is_pcie(root))
 			return;
 
 		if (control) {
@@ -529,7 +565,7 @@  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;
+	const char *acpi_hid;
 
 	root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
 	if (!root)
@@ -587,8 +623,16 @@  static int acpi_pci_root_add(struct acpi_device *device,
 
 	root->mcfg_addr = acpi_pci_root_get_mcfg_addr(handle);
 
-	is_pcie = strcmp(acpi_device_hid(device), "PNP0A08") == 0;
-	negotiate_os_control(root, &no_aspm, is_pcie);
+	acpi_hid = acpi_device_hid(root->device);
+	if (strcmp(acpi_hid, "PNP0A08") == 0)
+		root->bridge_type = ACPI_BRIDGE_TYPE_PCIE;
+	else if (strcmp(acpi_hid, "ACPI0016") == 0)
+		root->bridge_type = ACPI_BRIDGE_TYPE_CXL;
+	else
+		dev_warn(&device->dev, "unknown bridge type with hid: %s\n",
+			 acpi_hid);
+
+	negotiate_os_control(root, &no_aspm);
 
 	/*
 	 * TBD: Need PCI interface for enumeration/configuration of roots.