linux-kernel - [PATCH v2] cxl: Replace HDM decoder granularity magic numbers

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Date:   Mon, 29 Aug 2022 22:03:14 +0000
From:   Adam Manzanares <a.manzanares@...sung.com>
To:     "alison.schofield@...el.com" <alison.schofield@...el.com>,
        "vishal.l.verma@...el.com" <vishal.l.verma@...el.com>,
        "ira.weiny@...el.com" <ira.weiny@...el.com>,
        "bwidawsk@...nel.org" <bwidawsk@...nel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "dave@...olabs.net" <dave@...olabs.net>,
        "Jonathan.Cameron@...wei.com" <Jonathan.Cameron@...wei.com>
CC:     "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Adam Manzanares" <a.manzanares@...sung.com>
Subject: [PATCH v2] cxl: Replace HDM decoder granularity magic numbers

When reviewing the CFMWS parsing code that deals with the HDM decoders,
I noticed a couple of magic numbers. This commit replaces these magic numbers
with constants defined by the CXL 3.0 specification.

v2:
 - Change references to CXL 3.0 specification (David)
 - CXL_DECODER_MAX_GRANULARITY_ORDER -> CXL_DECODER_MAX_ENCODED_IG (Dan)

Signed-off-by: Adam Manzanares <a.manzanares@...sung.com>
---
 drivers/cxl/cxl.h | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index f680450f0b16..3ab81ad9d2e5 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -61,6 +61,10 @@
 #define CXL_HDM_DECODER0_SKIP_LOW(i) CXL_HDM_DECODER0_TL_LOW(i)
 #define CXL_HDM_DECODER0_SKIP_HIGH(i) CXL_HDM_DECODER0_TL_HIGH(i)
 
+/* HDM decoder control register constants CXL 3.0 8.2.5.19.7 */
+#define CXL_DECODER_MIN_GRANULARITY 256
+#define CXL_DECODER_MAX_ENCODED_IG 6
+
 static inline int cxl_hdm_decoder_count(u32 cap_hdr)
 {
 	int val = FIELD_GET(CXL_HDM_DECODER_COUNT_MASK, cap_hdr);
@@ -71,9 +75,9 @@ static inline int cxl_hdm_decoder_count(u32 cap_hdr)
 /* Encode defined in CXL 2.0 8.2.5.12.7 HDM Decoder Control Register */
 static inline int cxl_to_granularity(u16 ig, unsigned int *val)
 {
-	if (ig > 6)
+	if (ig > CXL_DECODER_MAX_ENCODED_IG)
 		return -EINVAL;
-	*val = 256 << ig;
+	*val = CXL_DECODER_MIN_GRANULARITY << ig;
 	return 0;
 }
 
@@ -96,7 +100,7 @@ static inline int cxl_to_ways(u8 eniw, unsigned int *val)
 
 static inline int granularity_to_cxl(int g, u16 *ig)
 {
-	if (g > SZ_16K || g < 256 || !is_power_of_2(g))
+	if (g > SZ_16K || g < CXL_DECODER_MIN_GRANULARITY || !is_power_of_2(g))
 		return -EINVAL;
 	*ig = ilog2(g) - 8;
 	return 0;
@@ -248,7 +252,6 @@ enum cxl_decoder_type {
  */
 #define CXL_DECODER_MAX_INTERLEAVE 16
 
-#define CXL_DECODER_MIN_GRANULARITY 256
 
 /**
  * struct cxl_decoder - Common CXL HDM Decoder Attributes
-- 
2.35.1