drivers/bcm2835: Add support for SWDIO direction control pin

Adds a new, optional configuration "bcm2835gpio_swdio_dir_num" to
the BCM2835 driver, to control the direction of an external buffer
driver IC in SWD mode. For example, this is needed to use a level-
shifting buffer, such as the SN74LVC2T45 used on the JTAG Hat

Change-Id: If5c146f310ecf8ceae85443b3670936467d2786d
Signed-off-by: Matthew Mets <matt@blinkinlabs.com>
Reviewed-on: http://openocd.zylin.com/6371
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

diff --git a/src/jtag/drivers/bcm2835gpio.c b/src/jtag/drivers/bcm2835gpio.c
index 40cb5aa0b6d4d9bf1cb31fd7c8ebd00e92a72894..6db4340e81f9d3c2c6126fc8cf832383405578b2 100644 (file)
--- a/src/jtag/drivers/bcm2835gpio.c
+++ b/src/jtag/drivers/bcm2835gpio.c
@@ -86,6 +86,8 @@ static int swclk_gpio = -1;
 static int swclk_gpio_mode;
 static int swdio_gpio = -1;
 static int swdio_gpio_mode;
+static int swdio_dir_gpio = -1;
+static int swdio_dir_gpio_mode;
 
 /* Transition delay coefficients */
 static int speed_coeff = 113714;
@@ -149,10 +151,20 @@ static int bcm2835gpio_reset(int trst, int srst)
 
 static void bcm2835_swdio_drive(bool is_output)
 {
-       if (is_output)
-               OUT_GPIO(swdio_gpio);
-       else
-               INP_GPIO(swdio_gpio);
+       if (swdio_dir_gpio > 0) {
+               if (is_output) {
+                       GPIO_SET = 1 << swdio_dir_gpio;
+                       OUT_GPIO(swdio_gpio);
+               } else {
+                       INP_GPIO(swdio_gpio);
+                       GPIO_CLR = 1 << swdio_dir_gpio;
+               }
+       } else {
+               if (is_output)
+                       OUT_GPIO(swdio_gpio);
+               else
+                       INP_GPIO(swdio_gpio);
+       }
 }
 
 static int bcm2835_swdio_read(void)
@@ -295,6 +307,15 @@ COMMAND_HANDLER(bcm2835gpio_handle_swd_gpionum_swdio)
        return ERROR_OK;
 }
 
+COMMAND_HANDLER(bcm2835gpio_handle_swd_dir_gpionum_swdio)
+{
+       if (CMD_ARGC == 1)
+               COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swdio_dir_gpio);
+
+       command_print(CMD, "BCM2835 num: swdio_dir = %d", swdio_dir_gpio);
+       return ERROR_OK;
+}
+
 COMMAND_HANDLER(bcm2835gpio_handle_speed_coeffs)
 {
        if (CMD_ARGC == 2) {
@@ -374,6 +395,13 @@ static const struct command_registration bcm2835gpio_command_handlers[] = {
                .help = "gpio number for swdio.",
                .usage = "[swdio]",
        },
+       {
+               .name = "bcm2835gpio_swdio_dir_num",
+               .handler = &bcm2835gpio_handle_swd_dir_gpionum_swdio,
+               .mode = COMMAND_CONFIG,
+               .help = "gpio number for swdio direction control pin (set=output mode, clear=input mode)",
+               .usage = "[swdio_dir]",
+       },
        {
                .name = "bcm2835gpio_srst_num",
                .handler = &bcm2835gpio_handle_jtag_gpionum_srst,
@@ -541,6 +569,12 @@ static int bcm2835gpio_init(void)
                OUT_GPIO(srst_gpio);
        }
 
+       if (swdio_dir_gpio != -1) {
+               swdio_dir_gpio_mode = MODE_GPIO(swdio_dir_gpio);
+               GPIO_SET = 1 << swdio_dir_gpio;
+               OUT_GPIO(swdio_dir_gpio);
+       }
+
        LOG_DEBUG("saved pinmux settings: tck %d tms %d tdi %d "
                  "tdo %d trst %d srst %d", tck_gpio_mode, tms_gpio_mode,
                  tdi_gpio_mode, tdo_gpio_mode, trst_gpio_mode, srst_gpio_mode);
@@ -567,5 +601,8 @@ static int bcm2835gpio_quit(void)
        if (srst_gpio != -1)
                SET_MODE_GPIO(srst_gpio, srst_gpio_mode);
 
+       if (swdio_dir_gpio != -1)
+               SET_MODE_GPIO(swdio_dir_gpio, swdio_dir_gpio_mode);
+
        return ERROR_OK;
 }