drivers/cmsis_dap: use quirk workarounds optionally

Introduce 'cmsis-dap quirk' command to enable and
disable quirk mode.

If enabled, disconnect and connect before a switch
sequence and do not use multiple packets pipelining.

Change-Id: I6576f7de9f6c98a25c3cf9eec9a456a23610d00d
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/7966
Tested-by: jenkins

doc/openocd.texi

@@ -2569,6 +2569,18 @@ In most cases need not to be specified and interfaces are searched by
 interface string or for user class interface.
 @end deffn
 
+@deffn {Command} {cmsis-dap quirk} [@option{enable}|@option{disable}]
+Enables or disables the following workarounds of known CMSIS-DAP adapter
+quirks:
+@itemize @minus
+@item disconnect and re-connect before sending a switch sequence
+@item packets pipelining is suppressed, only one packet at a time is
+submitted to the adapter
+@end itemize
+The quirk workarounds are disabled by default.
+The command without a parameter displays current setting.
+@end deffn
+
 @deffn {Command} {cmsis-dap info}
 Display various device information, like hardware version, firmware version, current bus status.
 @end deffn

src/jtag/drivers/cmsis_dap.c

@@ -861,9 +861,10 @@ static void cmsis_dap_swd_write_from_queue(struct cmsis_dap *dap)
 		goto skip;
 	}
 
-	dap->pending_fifo_put_idx = (dap->pending_fifo_put_idx + 1) % dap->packet_count;
+	unsigned int packet_count = dap->quirk_mode ? 1 : dap->packet_count;
+	dap->pending_fifo_put_idx = (dap->pending_fifo_put_idx + 1) % packet_count;
 	dap->pending_fifo_block_count++;
-	if (dap->pending_fifo_block_count > dap->packet_count)
+	if (dap->pending_fifo_block_count > packet_count)
 		LOG_ERROR("internal: too much pending writes %u", dap->pending_fifo_block_count);
 
 	return;
@@ -984,7 +985,8 @@ static void cmsis_dap_swd_read_process(struct cmsis_dap *dap, enum cmsis_dap_blo
 
 skip:
 	block->transfer_count = 0;
-	dap->pending_fifo_get_idx = (dap->pending_fifo_get_idx + 1) % dap->packet_count;
+	if (!dap->quirk_mode && dap->packet_count > 1)
+		dap->pending_fifo_get_idx = (dap->pending_fifo_get_idx + 1) % dap->packet_count;
 	dap->pending_fifo_block_count--;
 }
 
@@ -1079,7 +1081,8 @@ static void cmsis_dap_swd_queue_cmd(uint8_t cmd, uint32_t *dst, uint32_t data)
 		/* Not enough room in the queue. Run the queue. */
 		cmsis_dap_swd_write_from_queue(cmsis_dap_handle);
 
-		if (cmsis_dap_handle->pending_fifo_block_count >= cmsis_dap_handle->packet_count)
+		unsigned int packet_count = cmsis_dap_handle->quirk_mode ? 1 : cmsis_dap_handle->packet_count;
+		if (cmsis_dap_handle->pending_fifo_block_count >= packet_count)
 			cmsis_dap_swd_read_process(cmsis_dap_handle, CMSIS_DAP_BLOCKING);
 	}
 
@@ -1222,7 +1225,7 @@ static int cmsis_dap_swd_switch_seq(enum swd_special_seq seq)
 	if (swd_mode)
 		queued_retval = cmsis_dap_swd_run_queue();
 
-	if (seq != LINE_RESET &&
+	if (cmsis_dap_handle->quirk_mode && seq != LINE_RESET &&
 			(output_pins & (SWJ_PIN_SRST | SWJ_PIN_TRST))
 				== (SWJ_PIN_SRST | SWJ_PIN_TRST)) {
 		/* Following workaround deasserts reset on most adapters.
@@ -2220,6 +2223,19 @@ COMMAND_HANDLER(cmsis_dap_handle_backend_command)
 	return ERROR_OK;
 }
 
+COMMAND_HANDLER(cmsis_dap_handle_quirk_command)
+{
+	if (CMD_ARGC > 1)
+		return ERROR_COMMAND_SYNTAX_ERROR;
+
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_ENABLE(CMD_ARGV[0], cmsis_dap_handle->quirk_mode);
+
+	command_print(CMD, "CMSIS-DAP quirk workarounds %s",
+				  cmsis_dap_handle->quirk_mode ? "enabled" : "disabled");
+	return ERROR_OK;
+}
+
 static const struct command_registration cmsis_dap_subcommand_handlers[] = {
 	{
 		.name = "info",
@@ -2249,6 +2265,13 @@ static const struct command_registration cmsis_dap_subcommand_handlers[] = {
 		.help = "set the communication backend to use (USB bulk or HID).",
 		.usage = "(auto | usb_bulk | hid)",
 	},
+	{
+		.name = "quirk",
+		.handler = &cmsis_dap_handle_quirk_command,
+		.mode = COMMAND_ANY,
+		.help = "allow expensive workarounds of known adapter quirks.",
+		.usage = "[enable | disable]",
+	},
 #if BUILD_CMSIS_DAP_USB
 	{
 		.name = "usb",

src/jtag/drivers/cmsis_dap.h

@@ -52,6 +52,7 @@ struct cmsis_dap {
 	unsigned int pending_fifo_block_count;
 
 	uint16_t caps;
+	bool quirk_mode;	/* enable expensive workarounds */
 
 	uint32_t swo_buf_sz;
 	bool trace_enabled;