[PATCH V5 3/4] CryptoPkg: Add ECC related usage reference

["yi1 li" <yi1.li@intel.com>]

Describes the use cases under which ECC needs to be enabled,
and provides the impact on memory size for developers' reference.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Xiaoyu Lu <xiaoyux.lu@intel.com>
Cc: Guomin Jiang <guomin.jiang@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>

Signed-off-by: Yi Li <yi1.li@intel.com>
---
 CryptoPkg/CryptoPkg.dec | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/CryptoPkg/CryptoPkg.dec b/CryptoPkg/CryptoPkg.dec
index d9b64e5763..a3716864fd 100644
--- a/CryptoPkg/CryptoPkg.dec
+++ b/CryptoPkg/CryptoPkg.dec
@@ -83,7 +83,36 @@
 
   ## Enable/Disable the ECC feature in openssl library. The default is disabled.
   #  If ECC feature is disabled, all related source files will not be compiled.
+  # @Prompt Enable/Disable ECC feature in EDK II Crypto
   gEfiCryptoPkgTokenSpaceGuid.PcdOpensslEcEnabled|FALSE|BOOLEAN|0x0000003
+  # Set it to TRUE if:
+  # 1) Platform needs ECC in TLS, or asymmetric cryptography services such as
+  #    X509 certificate or PEM format data processing.
+  # 2) Platform needs to enable PcdCryptoServiceFamilyEnable.Ec service.
+  # Please note:
+  # ECC feature will cause a significant memory increase, approximate memory impact
+  # in below table for reference by platform developers with FW size limitations.
+  #                                   Uncompressed      LZMA Compressed
+  # CPU   CRYPTO_SERVICES    Module  EC=FALSE  EC=TRUE  EC=FALSE  EC=TRUE  Increase
+  # ====  ===============  ========  ========  =======  ========  =======  ========
+  # IA32  NONE             CryptoPei    21536    21568                         0 KB
+  # IA32  NONE             CryptoDxe    21632    21696                         0 KB
+  # IA32  NONE             CryptoSmm    22976    23072                         0 KB
+  # IA32  MIN_PEI          CryptoPei   248992   249120                         0 KB
+  # IA32  MIN_DXE_MIN_SMM  CryptoDxe   636672   829568    288520   401034    113 KB
+  # IA32  MIN_DXE_MIN_SMM  CryptoSmm   426048   601472    191517   296022    105 KB
+  # IA32  ALL              CryptoPei   423840   598976    189047   293759    104 KB
+  # IA32  ALL              CryptoDxe   645280   838144    292955   405277    113 KB
+  # IA32  ALL              CryptoSmm   441888   617184    198779   303628    105 KB
+  # X64   NONE             CryptoPei    29632    29664                         0 KB
+  # X64   NONE             CryptoDxe    29792    29792                         0 KB
+  # X64   NONE             CryptoSmm    31296    31296                         0 KB
+  # X64   MIN_PEI          CryptoPei   310784   310848                         0 KB
+  # X64   MIN_DXE_MIN_SMM  CryptoDxe   804288  1016256    311436   426596    115 KB
+  # X64   MIN_DXE_MIN_SMM  CryptoSmm   543776   733920    204483   310775    106 KB
+  # X64   ALL              CryptoPei   540384   730240    202494   308467    106 KB
+  # X64   ALL              CryptoDxe   815392  1027296    316228   431321    115 KB
+  # X64   ALL              CryptoSmm   563648   753696    213488   319644    106 KB
 
 [UserExtensions.TianoCore."ExtraFiles"]
   CryptoPkgExtra.uni
-- 
2.31.1.windows.1