interface/jtag_hat: Add interface configuration for the JTAG HAT

This adds support for the Blinkinlabs JTAG Hat, a Raspberry Pi
expansion board that provides JTAG and SWD connections via level-
shifting buffers.

Change-Id: I228bf6a18890b7c3d6679bbc63bfe39f726d8323
Signed-off-by: Matthew Mets <matt@blinkinlabs.com>
Reviewed-on: http://openocd.zylin.com/6372
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

tcl/interface/jtag_hat_rpi2.cfg

@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Blinkinlabs JTAG_Hat
+#
+# https://github.com/blinkinlabs/jtag_hat
+#
+
+adapter driver bcm2835gpio
+
+bcm2835gpio_peripheral_base 0x3F000000
+
+# Transition delay calculation: SPEED_COEFF/khz - SPEED_OFFSET
+# These depend on system clock, calibrated for stock 700MHz
+# bcm2835gpio_speed SPEED_COEFF SPEED_OFFSET
+bcm2835gpio_speed_coeffs 146203 36
+
+# Each of the JTAG lines need a gpio number set: tck tms tdi tdo
+# Header pin numbers: 23 22 19 21
+bcm2835gpio_jtag_nums 11 25 10 9
+
+# Each of the SWD lines need a gpio number set: swclk swdio
+# Header pin numbers: 23 22
+bcm2835gpio_swd_nums 11 25
+
+# Direction pin for SWDIO level shifting buffer
+bcm2835gpio_swdio_dir_num 6
+
+# If you define trst or srst, use appropriate reset_config
+# Header pin numbers: TRST - 26, SRST - 18
+
+bcm2835gpio_trst_num 7
+#reset_config trst_only
+
+bcm2835gpio_srst_num 24
+#reset_config srst_only
+
+# or if you have both connected
+#reset_config trst_and_srst