arm_adi_v5: do not deactivate power domains while trying to clear sticky error

[openocd] / src / target / arm_adi_v5.c

diff --git a/src/target/arm_adi_v5.c b/src/target/arm_adi_v5.c
index e62ac07577acce79c56af03dcd8b04764a5b0ffe..03e642bfeaec701b228a40195208cb652dc41507 100644 (file)
--- a/src/target/arm_adi_v5.c
+++ b/src/target/arm_adi_v5.c
@@ -652,6 +652,15 @@ int dap_dp_init(struct adiv5_dap *dap)
 
        dap_invalidate_cache(dap);
 
+       /*
+        * Early initialize dap->dp_ctrl_stat.
+        * In jtag mode only, if the following atomic reads fail and set the
+        * sticky error, it will trigger the clearing of the sticky. Without this
+        * initialization system and debug power would be disabled while clearing
+        * the sticky error bit.
+        */
+       dap->dp_ctrl_stat = CDBGPWRUPREQ | CSYSPWRUPREQ;
+
        for (size_t i = 0; i < 30; i++) {
                /* DP initialization */
 
@@ -660,7 +669,18 @@ int dap_dp_init(struct adiv5_dap *dap)
                        break;
        }
 
-       retval = dap_queue_dp_write(dap, DP_CTRL_STAT, SSTICKYERR);
+       /*
+        * This write operation clears the sticky error bit in jtag mode only and
+        * is ignored in swd mode. It also powers-up system and debug domains in
+        * both jtag and swd modes, if not done before.
+        * Actually we do not need to clear the sticky error here because it has
+        * been already cleared (if it was set) in the previous atomic read. This
+        * write could be removed, but this initial part of dap_dp_init() is the
+        * result of years of fine tuning and there are strong concerns about any
+        * unnecessary code change. It doesn't harm, so let's keep it here and
+        * preserve the historical sequence of read/write operations!
+        */
+       retval = dap_queue_dp_write(dap, DP_CTRL_STAT, dap->dp_ctrl_stat | SSTICKYERR);
        if (retval != ERROR_OK)
                return retval;
 
@@ -668,7 +688,6 @@ int dap_dp_init(struct adiv5_dap *dap)
        if (retval != ERROR_OK)
                return retval;
 
-       dap->dp_ctrl_stat = CDBGPWRUPREQ | CSYSPWRUPREQ;
        retval = dap_queue_dp_write(dap, DP_CTRL_STAT, dap->dp_ctrl_stat);
        if (retval != ERROR_OK)
                return retval;