[PATCH v3 04/18] cxl/pci: Add comments to cxl_hdm_decode_init()

[Robert Richter <rrichter@amd.com>]

There are various configuration cases of HDM decoder registers causing
different code paths. Add comments to cxl_hdm_decode_init() to better
explain them.

Signed-off-by: Robert Richter <rrichter@amd.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Gregory Price <gourry@gourry.net>
---
 drivers/cxl/core/pci.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index c49efc419285..6333a01e4f19 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -416,9 +416,17 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
 	if (global_ctrl & CXL_HDM_DECODER_ENABLE || (!hdm && info->mem_enabled))
 		return devm_cxl_enable_mem(&port->dev, cxlds);
 
+	/*
+	 * If the HDM Decoder Capability does not exist and DVSEC was
+	 * not setup, the DVSEC based emulation cannot be used.
+	 */
 	if (!hdm)
 		return -ENODEV;
 
+	/*
+	 * The HDM Decoder Capability exists but is globally disabled.
+	 */
+
 	/*
 	 * Per CXL 2.0 Section 8.1.3.8.3 and 8.1.3.8.4 DVSEC CXL Range 1 Base
 	 * [High,Low] when HDM operation is enabled the range register values
@@ -426,7 +434,8 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
 	 * DVSEC Range 1,2 to HDM Decoder Range 0,1. So, non-zero info->ranges
 	 * are expected even though Linux does not require or maintain that
 	 * match. If at least one DVSEC range is enabled and allowed, skip HDM
-	 * Decoder Capability Enable.
+	 * Decoder Capability Enable. Else, use the HDM Decoder Capability and
+	 * enable it.
 	 */
 	if (!info->mem_enabled) {
 		rc = devm_cxl_enable_hdm(&port->dev, cxlhdm);
-- 
2.39.5