cxl/hdm: Extend DVSEC range register emulation for region enumeration

One motivation for mapping range registers to decoder objects is
to use those settings for region autodiscovery.

The need to map a region for devices programmed to use range registers
is especially urgent now that the kernel no longer routes "Soft
Reserved" ranges in the memory map to device-dax by default. The CXL
memory range loses all access mechanisms.

Complete the implementation by marking the DPA reservation and setting
the endpoint-decoder state to signal autodiscovery. Note that the
default settings of ways=1 and granularity=4096 set in cxl_decode_init()
do not need to be updated.

Fixes: 09d09e0 ("cxl/dax: Create dax devices for CXL RAM regions")
Tested-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Gregory Price <gregory.price@memverge.com>
Link: https://lore.kernel.org/r/168012575521.221280.14177293493678527326.stgit@dwillia2-xfh.jf.intel.com
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/hdm.c

@@ -738,14 +738,20 @@ static int cxl_decoder_reset(struct cxl_decoder *cxld)
 	return 0;
 }
 
-static int cxl_setup_hdm_decoder_from_dvsec(struct cxl_port *port,
-					    struct cxl_decoder *cxld, int which,
-					    struct cxl_endpoint_dvsec_info *info)
+static int cxl_setup_hdm_decoder_from_dvsec(
+	struct cxl_port *port, struct cxl_decoder *cxld, u64 *dpa_base,
+	int which, struct cxl_endpoint_dvsec_info *info)
 {
+	struct cxl_endpoint_decoder *cxled;
+	u64 len;
+	int rc;
+
 	if (!is_cxl_endpoint(port))
 		return -EOPNOTSUPP;
 
-	if (!range_len(&info->dvsec_range[which]))
+	cxled = to_cxl_endpoint_decoder(&cxld->dev);
+	len = range_len(&info->dvsec_range[which]);
+	if (!len)
 		return -ENOENT;
 
 	cxld->target_type = CXL_DECODER_EXPANDER;
@@ -760,6 +766,16 @@ static int cxl_setup_hdm_decoder_from_dvsec(struct cxl_port *port,
 	cxld->flags |= CXL_DECODER_F_ENABLE | CXL_DECODER_F_LOCK;
 	port->commit_end = cxld->id;
 
+	rc = devm_cxl_dpa_reserve(cxled, *dpa_base, len, 0);
+	if (rc) {
+		dev_err(&port->dev,
+			"decoder%d.%d: Failed to reserve DPA range %#llx - %#llx\n (%d)",
+			port->id, cxld->id, *dpa_base, *dpa_base + len - 1, rc);
+		return rc;
+	}
+	*dpa_base += len;
+	cxled->state = CXL_DECODER_STATE_AUTO;
+
 	return 0;
 }
 
@@ -779,7 +795,8 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
 	} target_list;
 
 	if (should_emulate_decoders(info))
-		return cxl_setup_hdm_decoder_from_dvsec(port, cxld, which, info);
+		return cxl_setup_hdm_decoder_from_dvsec(port, cxld, dpa_base,
+							which, info);
 
 	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(which));
 	base = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(which));