[RFC PATCH 2/9] cxl/acpi: add OSC support

Ben Widawsky
2020-11-11T05:45:00Z

From: Vishal Verma <vishal.l.verma@intel.com>

Add support to advertise OS capabilities, and request OS control for CXL
features using the ACPI _OSC mechanism. Advertise support for all
possible CXL features, and attempt to request control too for all
possible features.

Based on a patch by Sean Kelley.

Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>

---

This uses a non-standard UUID for CXL and is meant as a change proposal
to the CXL specification. The definition for _OSC intermixes PCIe and
CXL Dwords, which makes a clean separation of CXL capabilities
difficult, if not impossible. This is therefore subject to change.

---
drivers/cxl/acpi.c | 210 ++++++++++++++++++++++++++++++++++++++++++++-
drivers/cxl/acpi.h | 18 ++++
2 files changed, 226 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index 26e4f73838a7..c3e2f7f6ea02 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -12,6 +12,16 @@
#include <linux/pci.h>
#include "acpi.h"

+/*
+ * TODO: These are global for now to save the OSC state.
+ * This works if OSC can be expected to be uniform for every ACPI0016 object.
+ * If that is not the case, revisit this. These need to be saved because
+ * relinquishing control of a previously granted capability is disallowed.
+ */
+static u32 cxl_osc_support_set;
+static u32 cxl_osc_control_set;
+static DEFINE_MUTEX(acpi_desc_lock);
+
static void acpi_cxl_desc_init(struct acpi_cxl_desc *acpi_desc, struct device *dev)
{
dev_set_drvdata(dev, acpi_desc);
@@ -74,6 +84,199 @@ static struct acpi_driver acpi_cxl_driver = {
},
};

+struct pci_osc_bit_struct {
+ u32 bit;
+ char *desc;
+};
+
+static struct pci_osc_bit_struct cxl_osc_support_bit[] = {
+ { CXL_OSC_PORT_REG_ACCESS_SUPPORT, "CXLPortRegAccess" },
+ { CXL_OSC_PORT_DEV_REG_ACCESS_SUPPORT, "CXLPortDevRegAccess" },
+ { CXL_OSC_PER_SUPPORT, "CXLProtocolErrorReporting" },
+ { CXL_OSC_NATIVE_HP_SUPPORT, "CXLNativeHotPlug" },
+};
+
+static struct pci_osc_bit_struct cxl_osc_control_bit[] = {
+ { CXL_OSC_MEM_ERROR_CONTROL, "CXLMemErrorReporting" },
+};
+
+/*
+ * CXL 2.0 spec UUID - unusable as it PCI and CXL OSC are mixed
+ * static u8 cxl_osc_uuid_str[] = "68F2D50B-C469-4d8A-BD3D-941A103FD3FC";
+ */
+/* New, proposed UUID for CXL-only OSC */
+static u8 cxl_osc_uuid_str[] = "A4D1629D-FF52-4888-BE96-E5CADE548DB1";
+
+static void decode_osc_bits(struct device *dev, char *msg, u32 word,
+ struct pci_osc_bit_struct *table, int size)
+{
+ char buf[80];
+ int i, len = 0;
+ struct pci_osc_bit_struct *entry;
+
+ buf[0] = '\0';
+ for (i = 0, entry = table; i < size; i++, entry++)
+ if (word & entry->bit)
+ len += scnprintf(buf + len, sizeof(buf) - len, "%s%s",
+ len ? " " : "", entry->desc);
+
+ dev_info(dev, "_OSC: %s [%s]\n", msg, buf);
+}
+
+static void decode_cxl_osc_support(struct device *dev, char *msg, u32 word)
+{
+ decode_osc_bits(dev, msg, word, cxl_osc_support_bit,
+ ARRAY_SIZE(cxl_osc_support_bit));
+}
+
+static void decode_cxl_osc_control(struct device *dev, char *msg, u32 word)
+{
+ decode_osc_bits(dev, msg, word, cxl_osc_control_bit,
+ ARRAY_SIZE(cxl_osc_control_bit));
+}
+
+static acpi_status acpi_cap_run_osc(acpi_handle handle,
+ const u32 *capbuf, u8 *uuid_str, u32 *retval)
+{
+ struct acpi_osc_context context = {
+ .uuid_str = uuid_str,
+ .rev = 1,
+ .cap.length = 20,
+ .cap.pointer = (void *)capbuf,
+ };
+ acpi_status status;
+
+ status = acpi_run_osc(handle, &context);
+ if (ACPI_SUCCESS(status)) {
+ *retval = *((u32 *)(context.ret.pointer + 8));
+ kfree(context.ret.pointer);
+ }
+ return status;
+}
+
+static acpi_status cxl_query_osc(acpi_handle handle, u32 support, u32 *control)
+{
+ acpi_status status;
+ u32 result, capbuf[5];
+
+ support &= CXL_OSC_SUPPORT_VALID_MASK;
+ support |= cxl_osc_support_set;
+
+ capbuf[OSC_QUERY_DWORD] = OSC_QUERY_ENABLE;
+ capbuf[CXL_OSC_SUPPORT_DWORD] = support;
+ if (control) {
+ *control &= CXL_OSC_CONTROL_VALID_MASK;
+ capbuf[CXL_OSC_CONTROL_DWORD] = *control | cxl_osc_control_set;
+ } else {
+ /* Run _OSC query only with existing controls. */
+ capbuf[CXL_OSC_CONTROL_DWORD] = cxl_osc_control_set;
+ }
+
+ status = acpi_cap_run_osc(handle, capbuf, cxl_osc_uuid_str, &result);
+ if (ACPI_SUCCESS(status)) {
+ cxl_osc_support_set = support;
+ if (control)
+ *control = result;
+ }
+ return status;
+}
+
+static acpi_status cxl_osc_advertise_support(acpi_handle handle, u32 flags)
+{
+ acpi_status status;
+
+ mutex_lock(&acpi_desc_lock);
+ status = cxl_query_osc(handle, flags, NULL);
+ mutex_unlock(&acpi_desc_lock);
+ return status;
+}
+
+/**
+ * cxl_osc_request_control - Request control of CXL root _OSC features.
+ * @adev: ACPI device for the PCI root bridge (or PCIe Root Complex).
+ * @mask: Mask of _OSC bits to request control of, place to store control mask.
+ * @req: Mask of _OSC bits the control of is essential to the caller.
+ **/
+static acpi_status cxl_osc_request_control(struct acpi_device *adev, u32 *mask, u32 req)
+{
+ acpi_handle handle = adev->handle;
+ struct device *dev = &adev->dev;
+ acpi_status status = AE_OK;
+ u32 ctrl, capbuf[5];
+
+ if (!mask)
+ return AE_BAD_PARAMETER;
+
+ ctrl = *mask & CXL_OSC_MEM_ERROR_CONTROL;
+ if ((ctrl & req) != req)
+ return AE_TYPE;
+
+ mutex_lock(&acpi_desc_lock);
+
+ *mask = ctrl | cxl_osc_control_set;
+ /* No need to evaluate _OSC if the control was already granted. */
+ if ((cxl_osc_control_set & ctrl) == ctrl)
+ goto out;
+
+ /* Need to check the available controls bits before requesting them. */
+ while (*mask) {
+ status = cxl_query_osc(handle, cxl_osc_support_set, mask);
+ if (ACPI_FAILURE(status))
+ goto out;
+ if (ctrl == *mask)
+ break;
+ decode_cxl_osc_control(dev, "platform does not support", ctrl & ~(*mask));
+ ctrl = *mask;
+ }
+
+ if ((ctrl & req) != req) {
+ decode_cxl_osc_control(dev, "not requesting control; platform does not support",
+ req & ~(ctrl));
+ status = AE_SUPPORT;
+ goto out;
+ }
+
+ capbuf[OSC_QUERY_DWORD] = 0;
+ capbuf[CXL_OSC_SUPPORT_DWORD] = cxl_osc_support_set;
+ capbuf[CXL_OSC_CONTROL_DWORD] = ctrl;
+ status = acpi_cap_run_osc(handle, capbuf, cxl_osc_uuid_str, mask);
+ if (ACPI_SUCCESS(status))
+ cxl_osc_control_set = *mask;
+out:
+ mutex_unlock(&acpi_desc_lock);
+ return status;
+}
+
+static int cxl_negotiate_osc(struct acpi_device *adev)
+{
+ u32 cxl_support, cxl_control, requested;
+ acpi_handle handle = adev->handle;
+ struct device *dev = &adev->dev;
+ acpi_status status;
+
+ /* Declare support for everything */
+ cxl_support = CXL_OSC_SUPPORT_VALID_MASK;
+ decode_cxl_osc_support(dev, "OS supports", cxl_support);
+ status = cxl_osc_advertise_support(handle, cxl_support);
+ if (ACPI_FAILURE(status)) {
+ dev_info(dev, "CXL_OSC failed (%s)\n", acpi_format_exception(status));
+ return -ENXIO;
+ }
+
+ /* Request control for everything */
+ cxl_control = CXL_OSC_CONTROL_VALID_MASK;
+ requested = cxl_control;
+ status = cxl_osc_request_control(adev, &cxl_control, CXL_OSC_MEM_ERROR_CONTROL);
+ if (ACPI_SUCCESS(status)) {
+ decode_cxl_osc_control(dev, "OS now controls", cxl_control);
+ } else {
+ decode_cxl_osc_control(dev, "OS requested", requested);
+ decode_cxl_osc_control(dev, "platform willing to grant", cxl_control);
+ dev_info(dev, "_OSC failed (%s)\n", acpi_format_exception(status));
+ }
+ return 0;
+}
+
/*
* If/when CXL support is defined by other platform firmware the kernel
* will need a mechanism to select between the platform specific version
@@ -84,6 +287,7 @@ int cxl_bus_prepared(struct pci_dev *pdev)
struct acpi_device *adev;
struct pci_dev *root_port;
struct device *root;
+ int rc;

root_port = pcie_find_root_port(pdev);
if (!root_port)
@@ -97,9 +301,11 @@ int cxl_bus_prepared(struct pci_dev *pdev)
if (!adev)
return -ENXIO;

- /* TODO: OSC enabling */
+ rc = cxl_negotiate_osc(adev);
+ if (rc)
+ dev_err(&pdev->dev, "Failed to negotiate OSC\n");

- return 0;
+ return rc;
}
EXPORT_SYMBOL_GPL(cxl_bus_prepared);

diff --git a/drivers/cxl/acpi.h b/drivers/cxl/acpi.h
index 011505475cc6..bf8d078e1b2a 100644
--- a/drivers/cxl/acpi.h
+++ b/drivers/cxl/acpi.h
@@ -10,6 +10,24 @@ struct acpi_cxl_desc {
struct device *dev;
};

+/* Indexes into _OSC Capabilities Buffer */
+#define CXL_OSC_SUPPORT_DWORD 1 /* DWORD 2 */
+#define CXL_OSC_CONTROL_DWORD 2 /* DWORD 3 */
+
+/* CXL Host Bridge _OSC: Capabilities DWORD 2: Support Field */
+#define CXL_OSC_PORT_REG_ACCESS_SUPPORT 0x00000001
+#define CXL_OSC_PORT_DEV_REG_ACCESS_SUPPORT 0x00000002
+#define CXL_OSC_PER_SUPPORT 0x00000004
+#define CXL_OSC_NATIVE_HP_SUPPORT 0x00000008
+#define CXL_OSC_SUPPORT_VALID_MASK (CXL_OSC_PORT_REG_ACCESS_SUPPORT | \
+ CXL_OSC_PORT_DEV_REG_ACCESS_SUPPORT | \
+ CXL_OSC_PER_SUPPORT | \
+ CXL_OSC_NATIVE_HP_SUPPORT)
+
+/* CXL Host Bridge _OSC: Capabilities DWORD 3: Control Field */
+#define CXL_OSC_MEM_ERROR_CONTROL 0x00000001
+#define CXL_OSC_CONTROL_VALID_MASK (CXL_OSC_MEM_ERROR_CONTROL)
+
int cxl_bus_prepared(struct pci_dev *pci_dev);

#endif /* __CXL_ACPI_H__ */
--
2.29.2