ADIv5: relocate memacess_tck cycles

When using an AP to access a memory (or a memory-mapped register),
some extra TCK (assuming JTAG) cycles should be added to ensure
the AP has enugh time to complete that access before trying to
collect the response.

The previous code was adding these cycles *before* trying to
access (read or write) data to that address, not *after*.  Fix
by putting the delays in the right location.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

diff --git a/src/target/arm_adi_v5.c b/src/target/arm_adi_v5.c
index 819dd290fd83990c231adb769c4fb396dfbc659a..d30dd50324ccbdce2d78ff839da7bcb97ca454a3 100644 (file)
--- a/src/target/arm_adi_v5.c
+++ b/src/target/arm_adi_v5.c
@@ -119,18 +119,6 @@ static int adi_jtag_dp_scan(struct swjdp_common *swjdp,
        jtag_set_end_state(TAP_IDLE);
        arm_jtag_set_instr(jtag_info, instr, NULL);
 
-       /* Add specified number of tck clocks before accessing memory bus */
-
-       /* REVISIT these TCK cycles should be *AFTER*  updating APACC, since
-        * they provide more time for the (MEM) AP to complete the read ...
-        * See "Minimum Response Time" for JTAG-DP, in the ADIv5 spec.
-        */
-       if ((instr == JTAG_DP_APACC)
-                       && ((reg_addr == AP_REG_DRW)
-                               || ((reg_addr & 0xF0) == AP_REG_BD0))
-                       && (swjdp->memaccess_tck != 0))
-               jtag_add_runtest(swjdp->memaccess_tck, jtag_set_end_state(TAP_IDLE));
-
        /* Scan out a read or write operation using some DP or AP register.
         * For APACC access with any sticky error flag set, this is discarded.
         */
@@ -152,6 +140,18 @@ static int adi_jtag_dp_scan(struct swjdp_common *swjdp,
 
        jtag_add_dr_scan(2, fields, jtag_get_end_state());
 
+       /* Add specified number of tck clocks after starting memory bus
+        * access, giving the hardware time to complete the access.
+        * They provide more time for the (MEM) AP to complete the read ...
+        * See "Minimum Response Time" for JTAG-DP, in the ADIv5 spec.
+        */
+       if ((instr == JTAG_DP_APACC)
+                       && ((reg_addr == AP_REG_DRW)
+                               || ((reg_addr & 0xF0) == AP_REG_BD0))
+                       && (swjdp->memaccess_tck != 0))
+               jtag_add_runtest(swjdp->memaccess_tck,
+                               jtag_set_end_state(TAP_IDLE));
+
        return jtag_get_error();
 }