igc: use FIELD_PREP and GENMASK for existing RX packet buffer size

Author: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>

Prepare for an upcoming patch that modifies the RX buffer size in TSN mode.
Refactor IGC_RXPBSIZE_EXP_BMC_DEFAULT and IGC_RXPBS_CFG_TS_EN using
FIELD_PREP and GENMASK to improve clarity and maintainability. Refactor
both macros for consistency, even though the upcoming patch only use
IGC_RXPBSIZE_EXP_BMC_DEFAULT.

The newly introduced macros follow the naming from the i226 SW User Manual
for easy reference.

I've tested IGC_RXPBSIZE_EXP_BMC_DEFAULT and IGC_RXPBS_CFG_TS_EN before
and after the refactoring, and their values remain unchanged.

Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
(cherry picked from commit 9cd87aa)
JIRA: https://issues.redhat.com/browse/RHEL-83571
Signed-off-by: Corinna Vinschen <vinschen@redhat.com>

Author: github-cygwin

drivers/net/ethernet/intel/igc/igc_defines.h

@@ -396,9 +396,20 @@
 #define IGC_RCTL_PMCF		0x00800000 /* pass MAC control frames */
 #define IGC_RCTL_SECRC		0x04000000 /* Strip Ethernet CRC */
 
-/* RXPBSIZE default value for Express and BMC buffer */
-#define IGC_RXPBSIZE_EXP_BMC_DEFAULT	0x000000A2
-#define IGC_RXPBS_CFG_TS_EN		0x80000000 /* Timestamp in Rx buffer */
+/* Mask for RX packet buffer size */
+#define IGC_RXPBSIZE_EXP_MASK		GENMASK(5, 0)
+#define IGC_BMC2OSPBSIZE_MASK		GENMASK(11, 6)
+/* Mask for timestamp in RX buffer */
+#define IGC_RXPBS_CFG_TS_EN_MASK	GENMASK(31, 31)
+/* High-priority RX packet buffer size (KB). Used for Express traffic when preemption is enabled */
+#define IGC_RXPBSIZE_EXP(x)		FIELD_PREP(IGC_RXPBSIZE_EXP_MASK, (x))
+/* BMC to OS packet buffer size in KB */
+#define IGC_BMC2OSPBSIZE(x)		FIELD_PREP(IGC_BMC2OSPBSIZE_MASK, (x))
+/* Enable RX packet buffer for timestamp descriptor, saving 16 bytes per packet if set */
+#define IGC_RXPBS_CFG_TS_EN		FIELD_PREP(IGC_RXPBS_CFG_TS_EN_MASK, 1)
+/* Default value following I225/I226 SW User Manual Section 8.3.1 */
+#define IGC_RXPBSIZE_EXP_BMC_DEFAULT ( \
+	IGC_RXPBSIZE_EXP(34) | IGC_BMC2OSPBSIZE(2))
 
 /* Mask for TX packet buffer size */
 #define IGC_TXPB0SIZE_MASK		GENMASK(5, 0)