[RFC PATCH v2 06/14] cxl/pci: Find the DOE mailbox which supports CDAT

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

From: Ira Weiny <ira.weiny@intel.com>

Memory devices need the CDAT data from the device.  This data is read
from a DOE mailbox which supports the CDAT protocol.

Search the DOE auxiliary devices for the one which supports the CDAT
protocol.  Cache that device to be used for future queries.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/cxl/cxl.h    |  3 +++
 drivers/cxl/cxlmem.h |  2 ++
 drivers/cxl/pci.c    | 43 ++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index a5a0be3f088b..a5a071056dac 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -75,6 +75,9 @@ static inline int cxl_hdm_decoder_count(u32 cap_hdr)
 #define CXLDEV_MBOX_BG_CMD_STATUS_OFFSET 0x18
 #define CXLDEV_MBOX_PAYLOAD_OFFSET 0x20
 
+#define CXL_DOE_PROTOCOL_COMPLIANCE 0
+#define CXL_DOE_PROTOCOL_TABLE_ACCESS 2
+
 /*
  * Using struct_group() allows for per register-block-type helper routines,
  * without requiring block-type agnostic code to include the prefix.
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 8d96d009ad90..176228d8c66d 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -97,6 +97,7 @@ struct cxl_mbox_cmd {
  * Currently only memory devices are represented.
  *
  * @dev: The device associated with this CXL state
+ * @cdat_doe: Auxiliary DOE device capabile of reading CDAT
  * @regs: Parsed register blocks
  * @payload_size: Size of space for payload
  *                (CXL 2.0 8.2.8.4.3 Mailbox Capabilities Register)
@@ -124,6 +125,7 @@ struct cxl_mbox_cmd {
 struct cxl_dev_state {
 	struct device *dev;
 
+	struct pci_doe_dev *cdat_doe;
 	struct cxl_regs regs;
 
 	size_t payload_size;
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index 0adc7798e0cf..adcabc0bcb38 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -472,12 +472,53 @@ static int cxl_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
 	return rc;
 }
 
+static int cxl_match_cdat_doe_device(struct device *dev, const void *data)
+{
+	const struct cxl_dev_state *cxlds = data;
+	struct auxiliary_device *adev;
+	struct pci_doe_dev *doe_dev;
+
+	/* First determine if this auxiliary device belongs to the cxlds */
+	if (cxlds->dev != dev->parent)
+		return 0;
+
+	adev = to_auxiliary_dev(dev);
+	doe_dev = container_of(adev, struct pci_doe_dev, adev);
+
+	/* If it is one of ours check for the CDAT protocol */
+	if (pci_doe_supports_prot(doe_dev, PCI_DVSEC_VENDOR_ID_CXL,
+				  CXL_DOE_PROTOCOL_TABLE_ACCESS))
+		return 1;
+
+	return 0;
+}
+
 static int cxl_setup_doe_devices(struct cxl_dev_state *cxlds)
 {
 	struct device *dev = cxlds->dev;
 	struct pci_dev *pdev = to_pci_dev(dev);
+	struct auxiliary_device *adev;
+	int rc;
 
-	return pci_doe_create_doe_devices(pdev);
+	rc = pci_doe_create_doe_devices(pdev);
+	if (rc)
+		return rc;
+
+	adev = auxiliary_find_device(NULL, cxlds, &cxl_match_cdat_doe_device);
+
+	if (adev) {
+		struct pci_doe_dev *doe_dev = container_of(adev,
+							   struct pci_doe_dev,
+							   adev);
+
+		/*
+		 * No reference need be taken.  The DOE device lifetime is
+		 * longer that the CXL device state lifetime
+		 */
+		cxlds->cdat_doe = doe_dev;
+	}
+
+	return 0;
 }
 
 static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
-- 
2.32.0