cxl/port: Read CDAT table

The per-device CDAT data provides performance data that is relevant for
mapping which CXL devices can participate in which CXL ranges by QTG
(QoS Throttling Group) (per ECN: CXL 2.0 CEDT CFMWS & QTG_DSM) [1]. The
QTG association specified in the ECN is advisory. Until the
cxl_acpi driver grows support for invoking the QTG _DSM method the CDAT
data is only of interest to userspace that may need it for debug
purposes.

Search the DOE mailboxes available, query CDAT data, cache the data and
make it available via a sysfs binary attribute per endpoint at:

/sys/bus/cxl/devices/endpointX/CDAT

...similar to other ACPI-structured table data in
/sys/firmware/ACPI/tables. The CDAT is relative to 'struct cxl_port'
objects since switches in addition to endpoints can host a CDAT
instance. Switch CDAT support is not implemented.

This does not support table updates at runtime. It will always provide
whatever was there when first cached. It is also the case that table
updates are not expected outside of explicit DPA address map affecting
commands like Set Partition with the immediate flag set. Given that the
driver does not support Set Partition with the immediate flag set there
is no current need for update support.

Link: https://www.computeexpresslink.org/spec-landing [1]
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Co-developed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
[djbw: drop in-kernel parsing infra for now, and other minor fixups]
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20220719205249.566684-7-ira.weiny@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 173 insertions, 0 deletions

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 7672789c3225..9240df53ed87 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -4,6 +4,7 @@
 #include <linux/device.h>
 #include <linux/delay.h>
 #include <linux/pci.h>
+#include <linux/pci-doe.h>
 #include <cxlpci.h>
 #include <cxlmem.h>
 #include <cxl.h>
@@ -452,3 +453,175 @@ hdm_init:
 	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_hdm_decode_init, CXL);
+
+#define CXL_DOE_TABLE_ACCESS_REQ_CODE		0x000000ff
+#define   CXL_DOE_TABLE_ACCESS_REQ_CODE_READ	0
+#define CXL_DOE_TABLE_ACCESS_TABLE_TYPE		0x0000ff00
+#define   CXL_DOE_TABLE_ACCESS_TABLE_TYPE_CDATA	0
+#define CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE	0xffff0000
+#define CXL_DOE_TABLE_ACCESS_LAST_ENTRY		0xffff
+#define CXL_DOE_PROTOCOL_TABLE_ACCESS 2
+
+static struct pci_doe_mb *find_cdat_doe(struct device *uport)
+{
+	struct cxl_memdev *cxlmd;
+	struct cxl_dev_state *cxlds;
+	unsigned long index;
+	void *entry;
+
+	cxlmd = to_cxl_memdev(uport);
+	cxlds = cxlmd->cxlds;
+
+	xa_for_each(&cxlds->doe_mbs, index, entry) {
+		struct pci_doe_mb *cur = entry;
+
+		if (pci_doe_supports_prot(cur, PCI_DVSEC_VENDOR_ID_CXL,
+					  CXL_DOE_PROTOCOL_TABLE_ACCESS))
+			return cur;
+	}
+
+	return NULL;
+}
+
+#define CDAT_DOE_REQ(entry_handle)					\
+	(FIELD_PREP(CXL_DOE_TABLE_ACCESS_REQ_CODE,			\
+		    CXL_DOE_TABLE_ACCESS_REQ_CODE_READ) |		\
+	 FIELD_PREP(CXL_DOE_TABLE_ACCESS_TABLE_TYPE,			\
+		    CXL_DOE_TABLE_ACCESS_TABLE_TYPE_CDATA) |		\
+	 FIELD_PREP(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE, (entry_handle)))
+
+static void cxl_doe_task_complete(struct pci_doe_task *task)
+{
+	complete(task->private);
+}
+
+struct cdat_doe_task {
+	u32 request_pl;
+	u32 response_pl[32];
+	struct completion c;
+	struct pci_doe_task task;
+};
+
+#define DECLARE_CDAT_DOE_TASK(req, cdt)                       \
+struct cdat_doe_task cdt = {                                  \
+	.c = COMPLETION_INITIALIZER_ONSTACK(cdt.c),           \
+	.request_pl = req,				      \
+	.task = {                                             \
+		.prot.vid = PCI_DVSEC_VENDOR_ID_CXL,        \
+		.prot.type = CXL_DOE_PROTOCOL_TABLE_ACCESS, \
+		.request_pl = &cdt.request_pl,                \
+		.request_pl_sz = sizeof(cdt.request_pl),      \
+		.response_pl = cdt.response_pl,               \
+		.response_pl_sz = sizeof(cdt.response_pl),    \
+		.complete = cxl_doe_task_complete,            \
+		.private = &cdt.c,                            \
+	}                                                     \
+}
+
+static int cxl_cdat_get_length(struct device *dev,
+			       struct pci_doe_mb *cdat_doe,
+			       size_t *length)
+{
+	DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(0), t);
+	int rc;
+
+	rc = pci_doe_submit_task(cdat_doe, &t.task);
+	if (rc < 0) {
+		dev_err(dev, "DOE submit failed: %d", rc);
+		return rc;
+	}
+	wait_for_completion(&t.c);
+	if (t.task.rv < sizeof(u32))
+		return -EIO;
+
+	*length = t.response_pl[1];
+	dev_dbg(dev, "CDAT length %zu\n", *length);
+
+	return 0;
+}
+
+static int cxl_cdat_read_table(struct device *dev,
+			       struct pci_doe_mb *cdat_doe,
+			       struct cxl_cdat *cdat)
+{
+	size_t length = cdat->length;
+	u32 *data = cdat->table;
+	int entry_handle = 0;
+
+	do {
+		DECLARE_CDAT_DOE_TASK(CDAT_DOE_REQ(entry_handle), t);
+		size_t entry_dw;
+		u32 *entry;
+		int rc;
+
+		rc = pci_doe_submit_task(cdat_doe, &t.task);
+		if (rc < 0) {
+			dev_err(dev, "DOE submit failed: %d", rc);
+			return rc;
+		}
+		wait_for_completion(&t.c);
+		/* 1 DW header + 1 DW data min */
+		if (t.task.rv < (2 * sizeof(u32)))
+			return -EIO;
+
+		/* Get the CXL table access header entry handle */
+		entry_handle = FIELD_GET(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE,
+					 t.response_pl[0]);
+		entry = t.response_pl + 1;
+		entry_dw = t.task.rv / sizeof(u32);
+		/* Skip Header */
+		entry_dw -= 1;
+		entry_dw = min(length / sizeof(u32), entry_dw);
+		/* Prevent length < 1 DW from causing a buffer overflow */
+		if (entry_dw) {
+			memcpy(data, entry, entry_dw * sizeof(u32));
+			length -= entry_dw * sizeof(u32);
+			data += entry_dw;
+		}
+	} while (entry_handle != CXL_DOE_TABLE_ACCESS_LAST_ENTRY);
+
+	return 0;
+}
+
+/**
+ * read_cdat_data - Read the CDAT data on this port
+ * @port: Port to read data from
+ *
+ * This call will sleep waiting for responses from the DOE mailbox.
+ */
+void read_cdat_data(struct cxl_port *port)
+{
+	struct pci_doe_mb *cdat_doe;
+	struct device *dev = &port->dev;
+	struct device *uport = port->uport;
+	size_t cdat_length;
+	int rc;
+
+	cdat_doe = find_cdat_doe(uport);
+	if (!cdat_doe) {
+		dev_dbg(dev, "No CDAT mailbox\n");
+		return;
+	}
+
+	port->cdat_available = true;
+
+	if (cxl_cdat_get_length(dev, cdat_doe, &cdat_length)) {
+		dev_dbg(dev, "No CDAT length\n");
+		return;
+	}
+
+	port->cdat.table = devm_kzalloc(dev, cdat_length, GFP_KERNEL);
+	if (!port->cdat.table)
+		return;
+
+	port->cdat.length = cdat_length;
+	rc = cxl_cdat_read_table(dev, cdat_doe, &port->cdat);
+	if (rc) {
+		/* Don't leave table data allocated on error */
+		devm_kfree(dev, port->cdat.table);
+		port->cdat.table = NULL;
+		port->cdat.length = 0;
+		dev_err(dev, "CDAT data read error\n");
+	}
+}
+EXPORT_SYMBOL_NS_GPL(read_cdat_data, CXL);