[PATCH] cxl/hdm: Fix decoder count calculation

[Ben Widawsky <ben.widawsky@intel.com>]

The decoder count in the HDM decoder capability structure is an encoded
field. As defined in the spec:

Decoder Count: Reports the number of memory address decoders implemented
by the component.
0 – 1 Decoder
1 – 2 Decoders
2 – 4 Decoders
3 – 6 Decoders
4 – 8 Decoders
5 – 10 DecodersAll other values are reserved

Nothing is actually fixed by this as nothing actually used this mapping
yet.

Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
 drivers/cxl/core.c | 3 ++-
 drivers/cxl/cxl.h  | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/core.c b/drivers/cxl/core.c
index cda09a9cd98e..92db02fe7aa8 100644
--- a/drivers/cxl/core.c
+++ b/drivers/cxl/core.c
@@ -666,7 +666,8 @@ void cxl_probe_component_regs(struct device *dev, void __iomem *base,
 
 			hdr = readl(register_block);
 
-			decoder_cnt = FIELD_GET(CXL_HDM_DECODER_COUNT_MASK, hdr);
+			decoder_cnt =
+				cxl_hdm_decoder_count(FIELD_GET(CXL_HDM_DECODER_COUNT_MASK, hdr));
 			length = 0x20 * decoder_cnt + 0x10;
 
 			map->hdm_decoder.valid = true;
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 1ffc5e07e24d..f0dff7d96286 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -35,6 +35,7 @@
 /* HDM decoders CXL 2.0 8.2.5.12 CXL HDM Decoder Capability Structure */
 #define CXL_HDM_DECODER_CAP_OFFSET 0x0
 #define   CXL_HDM_DECODER_COUNT_MASK GENMASK(3, 0)
+#define	    cxl_hdm_decoder_count(bits) ((bits) == 0 ? 1 : (bits) * 2)
 #define   CXL_HDM_DECODER_TARGET_COUNT_MASK GENMASK(7, 4)
 #define CXL_HDM_DECODER0_BASE_LOW_OFFSET 0x10
 #define CXL_HDM_DECODER0_BASE_HIGH_OFFSET 0x14
-- 
2.32.0