From: Ben Widawsky <ben.widawsky@intel.com>

Add a trivial handler for now to cover the root bridge
where we could do some error checking in future.

* Ben. I lifted this one from you but you didn't sign off on it.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 hw/cxl/cxl-component-utils.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
index be2c5599d6..0edf717387 100644
--- a/hw/cxl/cxl-component-utils.c
+++ b/hw/cxl/cxl-component-utils.c
@@ -28,6 +28,31 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
     }
 }
 
+static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
+                             uint32_t value)
+{
+    ComponentRegisters *cregs = &cxl_cstate->crb;
+    uint32_t *cache_mem = cregs->cache_mem_registers;
+    bool should_commit = false;
+
+    switch (offset) {
+    case A_CXL_HDM_DECODER0_CTRL:
+        should_commit = FIELD_EX32(value, CXL_HDM_DECODER0_CTRL, COMMIT);
+        break;
+    default:
+        break;
+    }
+
+    memory_region_transaction_begin();
+    stl_le_p((uint8_t *)cache_mem + offset, value);
+    if (should_commit) {
+        ARRAY_FIELD_DP32(cache_mem, CXL_HDM_DECODER0_CTRL, COMMIT, 0);
+        ARRAY_FIELD_DP32(cache_mem, CXL_HDM_DECODER0_CTRL, ERROR, 0);
+        ARRAY_FIELD_DP32(cache_mem, CXL_HDM_DECODER0_CTRL, COMMITTED, 1);
+    }
+    memory_region_transaction_commit();
+}
+
 static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
                                     unsigned size)
 {
@@ -38,6 +63,12 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
 
     if (cregs->special_ops && cregs->special_ops->write) {
         cregs->special_ops->write(cxl_cstate, offset, value, size);
+        return;
+    }
+
+    if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
+        offset <= A_CXL_HDM_DECODER0_TARGET_LIST_HI) {
+        dumb_hdm_handler(cxl_cstate, offset, value);
     } else {
         cregs->cache_mem_registers[offset / 4] = value;
     }
-- 
2.32.0