mips: change in restoring debug working register

In current devel code there are 3 functions (related to m4k code) that need to restore register 8 from pracc stack:
mips32_pracc_read_u32()
mips32_cp0_read()
mips32_pracc_write_mem_generic()

And mips32_pracc_read_mem() needs to restore regs 8 and 9 from pracc stack.

Values in this registers should be the same as read by mips32_pracc_read_regs() when entering debug
mode and can be modified by mips32_pracc_write_regs() when leaving debug mode.
There is no need to read their values from the processor registers every time.

The fields reg8 and reg9 are added to struct mips_ejtag to store these register values
and the call to mips32_save_context() is shifted in mips_m4k_debug_entry() in order
to store them before any other function needs to restore these registers.
For the same reason in function mips_m4k_step() the call to mips_m4k_set_breakpoint(), if needed,
should be made after calling mips_m4k_debug_entry().
For single word write the number of pracc accesses are now 9 or 8, from 13 or 12 in current code,
single word read takes now 10 instead of 12.

This patch is really the first in a set of patches for an alternate m4k pracc code
much faster that current code. At least for me with pic32mx works fine.

Change-Id: Ibd9df5e8b9f78ce05a180949ba6a561c761b61d6
Signed-off-by: Salvador Arroyo <sarroyofdez@yahoo.es>
Reviewed-on: http://openocd.zylin.com/1146
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

1 files changed, 5 insertions, 5 deletions

diff --git a/src/target/mips_m4k.c b/src/target/mips_m4k.c
index fb4c3762..485f4e8c 100644
--- a/src/target/mips_m4k.c
+++ b/src/target/mips_m4k.c
@@ -90,14 +90,14 @@ static int mips_m4k_debug_entry(struct target *target)
 	/* make sure stepping disabled, SSt bit in CP0 debug register cleared */
 	mips_ejtag_config_step(ejtag_info, 0);
 
+	mips32_save_context(target);
+
 	/* make sure break unit configured */
 	mips32_configure_break_unit(target);
 
 	/* attempt to find halt reason */
 	mips_m4k_examine_debug_reason(target);
 
-	mips32_save_context(target);
-
 	/* default to mips32 isa, it will be changed below if required */
 	mips32->isa_mode = MIPS32_ISA_MIPS32;
 
@@ -558,12 +558,12 @@ static int mips_m4k_step(struct target *target, int current,
 	/* registers are now invalid */
 	register_cache_invalidate(mips32->core_cache);
 
+	LOG_DEBUG("target stepped ");
+	mips_m4k_debug_entry(target);
+
 	if (breakpoint)
 		mips_m4k_set_breakpoint(target, breakpoint);
 
-	LOG_DEBUG("target stepped ");
-
-	mips_m4k_debug_entry(target);
 	target_call_event_callbacks(target, TARGET_EVENT_HALTED);
 
 	return ERROR_OK;