This describes requirement of e500 and e500v2 processor to support external
debugger.
It also provide an insight of the configuration switch required and their
description.
Signed-off-by: Radu Lazarescu <radu.lazare...@freescale.com>
Signed-off-by: Marius Grigoras <marius.grigo...@freescale.com>
Signed-off-by: Prabhakar Kushwaha <prabha...@freescale.com>
---
Based upon git://git.denx.de/u-boot.git branch master
Changes for v2:
- Recreated README.mpc85xx
- Added #define in README
Tested on
- SoC having E500 Family processor (P1010RDB, BSC9131RDB)
- SoC having E500MC Family processor (P4080DS, P3041DS)
README | 14 ++++++++++++++
doc/README.mpc85xx | 23 +++++++++++++++++++++++
2 files changed, 37 insertions(+), 0 deletions(-)
create mode 100644 doc/README.mpc85xx
diff --git a/README b/README
index 8964672..48e50ed 100644
--- a/README
+++ b/README
@@ -3347,6 +3347,20 @@ Low Level (hardware related) configuration options:
be used if available. These functions may be faster under some
conditions but may increase the binary size.
+E500 (MPC85xx) External Debug Support
+-------------------------------------
+-CONFIG_E500
+ Enables BOOKE e500 family.It includes e500, e500v2 e500mc,
+ e5500 processor etc.
+
+- CONFIG_SYS_PPC_E500_DEBUG_TLB
+ Enables a temporary TLB entry to be used during boot to work
+ around limitations in e500v1 and e500v2 external debugger
+ support. This reduces the portions of the boot code where
+ breakpoints and single stepping do not work. The value of this
+ symbol should be set to the TLB1 entry to be used for this
+ purpose.
+
Freescale QE/FMAN Firmware Support:
-----------------------------------
diff --git a/doc/README.mpc85xx b/doc/README.mpc85xx
new file mode 100644
index 0000000..dbd74be
--- /dev/null
+++ b/doc/README.mpc85xx
@@ -0,0 +1,23 @@
+External Debug Support
+----------------------
+
+Freescale's e500v1 and e500v2 cores (used in mpc85xx chips) have some
+restrictions on external debugging (JTAG). In particular, for the debugger to
+be able to receive control after a single step or breakpoint:
+ - MSR[DE] must be set
+ - A valid opcode must be fetchable, through the MMU, from the debug
+ exception vector (IVPR + IVOR15).
+
+To maximize the time during which this requirement is met, U-Boot sets MSR[DE]
+immediately on entry and keeps it set. It also uses a temporary TLB to keep a
+mapping to a valid opcode at the debug exception vector, even if we normally
+don't support exception vectors being used that early, and that's not the area
+where U-Boot currently executes from.
+
+Note that there may still be some small windows where debugging will not work,
+such as in between updating IVPR and IVOR15.
+
+Config Switches:
+----------------
+
+Please refer README section "MPC85xx External Debug Support"
--
1.7.5.4
_______________________________________________
U-Boot mailing list
U-Boot@lists.denx.de
http://lists.denx.de/mailman/listinfo/u-boot
