X-Git-Url: https://review.openocd.org/gitweb?p=openocd.git;a=blobdiff_plain;f=src%2Ftarget%2Fadi_v5_jtag.c;h=75461c3fa7e8bf95fd627e8914bf4136d56c6a92;hp=185bd54375baae01997a8de3aa663466b6ae4350;hb=b48d1f66378fac886d5bc32d7302da48c89d8a75;hpb=4333840ee3d6d79299bf90b719a3c1628c688690

diff --git a/src/target/adi_v5_jtag.c b/src/target/adi_v5_jtag.c
index 185bd54375..75461c3fa7 100644
--- a/src/target/adi_v5_jtag.c
+++ b/src/target/adi_v5_jtag.c
@@ -191,28 +191,38 @@ static int jtagdp_transaction_endcheck(struct adiv5_dap *dap)
 
 	/* too expensive to call keep_alive() here */
 
-#if 0
-	/* Danger!!!! BROKEN!!!! */
-	adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
-			DP_CTRL_STAT, DPAP_READ, 0, &ctrlstat);
-	/* Danger!!!! BROKEN!!!! Why will jtag_execute_queue() fail here????
-	R956 introduced the check on return value here and now Michael Schwingen reports
-	that this code no longer works....
-
-	https://lists.berlios.de/pipermail/openocd-development/2008-September/003107.html
-	*/
-	if ((retval = jtag_execute_queue()) != ERROR_OK)
-	{
-		LOG_ERROR("BUG: Why does this fail the first time????");
-	}
-	/* Why??? second time it works??? */
-#endif
+	/* Here be dragons!
+	 *
+	 * It is easy to be in a JTAG clock range where the target
+	 * is not operating in a stable fashion. This happens
+	 * for a few reasons:
+	 *
+	 * - the user may construct a simple test case to try to see
+	 * if a higher JTAG clock works to eke out more performance.
+	 * This simple case may pass, but more complex situations can
+	 * fail.
+	 *
+	 * - The mostly works JTAG clock rate and the complete failure
+	 * JTAG clock rate may be as much as 2-4x apart. This seems
+	 * to be especially true on RC oscillator driven parts.
+	 *
+	 * So: even if calling adi_jtag_scan_inout_check_u32() multiple
+	 * times here seems to "make things better here", it is just
+	 * hiding problems with too high a JTAG clock.
+	 *
+	 * Note that even if some parts have RCLK/RTCK, that doesn't
+	 * mean that RCLK/RTCK is the *correct* rate to run the JTAG
+	 * interface at, i.e. RCLK/RTCK rates can be "too high", especially
+	 * before the RC oscillator phase is not yet complete.
+	 */
 
 	/* Post CTRL/STAT read; discard any previous posted read value
 	 * but collect its ACK status.
 	 */
-	adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
+	retval = adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
 			DP_CTRL_STAT, DPAP_READ, 0, &ctrlstat);
+	if (retval != ERROR_OK)
+		return retval;
 	if ((retval = jtag_execute_queue()) != ERROR_OK)
 		return retval;
 
@@ -246,8 +256,10 @@ static int jtagdp_transaction_endcheck(struct adiv5_dap *dap)
 				return ERROR_JTAG_DEVICE_ERROR;
 			}
 
-			adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
+			retval = adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
 					DP_CTRL_STAT, DPAP_READ, 0, &ctrlstat);
+			if (retval != ERROR_OK)
+				return retval;
 			if ((retval = dap_run(dap)) != ERROR_OK)
 				return retval;
 			dap->ack = dap->ack & 0x7;
@@ -292,12 +304,16 @@ static int jtagdp_transaction_endcheck(struct adiv5_dap *dap)
 				LOG_ERROR("JTAG-DP STICKY ERROR");
 
 			/* Clear Sticky Error Bits */
-			adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
+			retval = adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
 					DP_CTRL_STAT, DPAP_WRITE,
 					dap->dp_ctrl_stat | SSTICKYORUN
 						| SSTICKYERR, NULL);
-			adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
+			if (retval != ERROR_OK)
+				return retval;
+			retval = adi_jtag_scan_inout_check_u32(dap, JTAG_DP_DPACC,
 					DP_CTRL_STAT, DPAP_READ, 0, &ctrlstat);
+			if (retval != ERROR_OK)
+				return retval;
 			if ((retval = dap_run(dap)) != ERROR_OK)
 				return retval;
 
@@ -376,7 +392,7 @@ static int jtag_ap_q_bankselect(struct adiv5_dap *dap, unsigned reg)
 		return ERROR_OK;
 	dap->ap_bank_value = select_ap_bank;
 
-	select_ap_bank |= dap->apsel;
+	select_ap_bank |= dap->ap_current;
 
 	return jtag_dp_q_write(dap, DP_SELECT, select_ap_bank);
 }