From: Alastair D'Silva <alast...@d-silva.org>

This patch retrieves the serial number of the card and makes it available
to consumers of the ocxl driver via the ocxl_fn struct.

Signed-off-by: Alastair D'Silva <alast...@d-silva.org>
---
 drivers/misc/ocxl/config.c | 46 ++++++++++++++++++++++++++++++++++++++
 include/misc/ocxl.h        |  1 +
 2 files changed, 47 insertions(+)

diff --git a/drivers/misc/ocxl/config.c b/drivers/misc/ocxl/config.c
index fb0c3b6f8312..a9203c309365 100644
--- a/drivers/misc/ocxl/config.c
+++ b/drivers/misc/ocxl/config.c
@@ -71,6 +71,51 @@ static int find_dvsec_afu_ctrl(struct pci_dev *dev, u8 
afu_idx)
        return 0;
 }
 
+/**
+ * Find a related PCI device (function 0)
+ * @device: PCI device to match
+ *
+ * Returns a pointer to the related device, or null if not found
+ */
+static struct pci_dev *get_function_0(struct pci_dev *dev)
+{
+       unsigned int devfn = PCI_DEVFN(PCI_SLOT(dev->devfn), 0); // Look for 
function 0
+
+       return pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
+                                       dev->bus->number, devfn);
+}
+
+static void read_serial(struct pci_dev *dev, struct ocxl_fn_config *fn)
+{
+       u32 low, high;
+       int pos;
+
+       pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DSN);
+       if (pos) {
+               pci_read_config_dword(dev, pos + 0x04, &low);
+               pci_read_config_dword(dev, pos + 0x08, &high);
+
+               fn->serial = low | ((u64)high) << 32;
+
+               return;
+       }
+
+       if (PCI_FUNC(dev->devfn) != 0) {
+               struct pci_dev *related = get_function_0(dev);
+
+               if (!related) {
+                       fn->serial = 0;
+                       return;
+               }
+
+               read_serial(related, fn);
+               pci_dev_put(related);
+               return;
+       }
+
+       fn->serial = 0;
+}
+
 static void read_pasid(struct pci_dev *dev, struct ocxl_fn_config *fn)
 {
        u16 val;
@@ -208,6 +253,7 @@ int ocxl_config_read_function(struct pci_dev *dev, struct 
ocxl_fn_config *fn)
        int rc;
 
        read_pasid(dev, fn);
+       read_serial(dev, fn);
 
        rc = read_dvsec_tl(dev, fn);
        if (rc) {
diff --git a/include/misc/ocxl.h b/include/misc/ocxl.h
index 6f7c02f0d5e3..9843051c3c5b 100644
--- a/include/misc/ocxl.h
+++ b/include/misc/ocxl.h
@@ -46,6 +46,7 @@ struct ocxl_fn_config {
        int dvsec_afu_info_pos; /* offset of the AFU information DVSEC */
        s8 max_pasid_log;
        s8 max_afu_index;
+       u64 serial;
 };
 
 enum ocxl_endian {
-- 
2.21.0

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