jtag: Add an option to ignore the bypass bit

Some CPU wrongly indicate the bypas bit in the codeid.
It's the case of the NanoXplore NG-ULTRA chip that export a
configurable (and potentially invalid) ID for one of
its component.
Add an option to ignore it.

Signed-off-by: Adrien Grassein <adrien.grassein@gmail.com>
Change-Id: Ic59743f23bfc4d4e23da0e8535fec8ca9e87ff1a
Reviewed-on: https://review.openocd.org/c/openocd/+/6802
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Oleksij Rempel <linux@rempel-privat.de>

src/jtag/core.c

@@ -1273,7 +1273,7 @@ static int jtag_examine_chain(void)
 			jtag_tap_init(tap);
 		}
 
-		if ((idcode & 1) == 0) {
+		if ((idcode & 1) == 0 && !tap->ignore_bypass) {
 			/* Zero for LSB indicates a device in bypass */
 			LOG_INFO("TAP %s does not have valid IDCODE (idcode=0x%" PRIx32 ")",
 					tap->dotted_name, idcode);

src/jtag/hla/hla_tcl.c

@@ -59,6 +59,7 @@ static int jim_newtap_expected_id(struct jim_nvp *n, struct jim_getopt_info *goi
 #define NTAP_OPT_DISABLED  4
 #define NTAP_OPT_EXPECTED_ID 5
 #define NTAP_OPT_VERSION   6
+#define NTAP_OPT_BYPASS    7
 
 static int jim_hl_newtap_cmd(struct jim_getopt_info *goi)
 {
@@ -75,6 +76,7 @@ static int jim_hl_newtap_cmd(struct jim_getopt_info *goi)
 		{ .name = "-disable",       .value = NTAP_OPT_DISABLED },
 		{ .name = "-expected-id",       .value = NTAP_OPT_EXPECTED_ID },
 		{ .name = "-ignore-version",       .value = NTAP_OPT_VERSION },
+		{ .name = "-ignore-bypass",       .value = NTAP_OPT_BYPASS },
 		{ .name = NULL, .value = -1},
 	};
 

src/jtag/jtag.h

@@ -135,6 +135,9 @@ struct jtag_tap {
 	/** Flag saying whether to ignore version field in expected_ids[] */
 	bool ignore_version;
 
+	/** Flag saying whether to ignore the bypass bit in the code */
+	bool ignore_bypass;
+
 	/** current instruction */
 	uint8_t *cur_instr;
 	/** Bypass register selected */

src/jtag/tcl.c

@@ -470,6 +470,7 @@ static int jim_newtap_expected_id(struct jim_nvp *n, struct jim_getopt_info *goi
 #define NTAP_OPT_DISABLED  4
 #define NTAP_OPT_EXPECTED_ID 5
 #define NTAP_OPT_VERSION   6
+#define NTAP_OPT_BYPASS    7
 
 static int jim_newtap_ir_param(struct jim_nvp *n, struct jim_getopt_info *goi,
 	struct jtag_tap *tap)
@@ -532,6 +533,7 @@ static int jim_newtap_cmd(struct jim_getopt_info *goi)
 		{ .name = "-disable",       .value = NTAP_OPT_DISABLED },
 		{ .name = "-expected-id",       .value = NTAP_OPT_EXPECTED_ID },
 		{ .name = "-ignore-version",       .value = NTAP_OPT_VERSION },
+		{ .name = "-ignore-bypass",       .value = NTAP_OPT_BYPASS },
 		{ .name = NULL,       .value = -1 },
 	};
 
@@ -617,6 +619,9 @@ static int jim_newtap_cmd(struct jim_getopt_info *goi)
 		    case NTAP_OPT_VERSION:
 			    tap->ignore_version = true;
 			    break;
+		    case NTAP_OPT_BYPASS:
+			    tap->ignore_bypass = true;
+			    break;
 		}	/* switch (n->value) */
 	}	/* while (goi->argc) */
 
@@ -887,6 +892,7 @@ static const struct command_registration jtag_subcommand_handlers[] = {
 			"['-enable'|'-disable'] "
 			"['-expected_id' number] "
 			"['-ignore-version'] "
+			"['-ignore-bypass'] "
 			"['-ircapture' number] "
 			"['-mask' number]",
 	},