ast-bmc: Document BMC scratch register
ASPEED BMCs use SIO register 0x29 to configure host firmwrae settings.
This documents those setings as currently used by Hostboot in [1].
Despite the naming, these settings are relevant for ast2500 systems as
well.
[1] src/usr/initservice/bootconfig/bootconfig_ast2400.H
#define BMC_SIO_SCR28 0x28
#define BOOT_FLAGS_VERSION 0x42
+/*
+ * SIO Register 0x29: Boot Flags (normal bit ordering)
+ *
+ * [7:6] Hostboot Boot mode:
+ * 00 : Normal
+ * 01 : Terminate on first error
+ * 10 : istep mode
+ * 11 : reserved
+ * [5:4] Boot options
+ * 00 : reserved
+ * 01 : Memboot
+ * 10 : Clear gard
+ * 11 : reserved
+ * [ 3 ] BMC mbox PNOR driver
+ * [2:0] Hostboot Log level:
+ * 000 : Normal
+ * 001 : Enable Scan trace
+ * xxx : reserved
+ */
+
#define BMC_SIO_SCR29 0x29
#define BMC_SIO_SCR29_MEMBOOT 0x10
