drivers/bcm2835gpio: Fully restore GPIOs after use

Restore outputs to their initial output level.

Signed-off-by: Steve Marple <stevemarple@googlemail.com>
Change-Id: I82402fd7b59d944f81c0ea7859ac499943901f82
Reviewed-on: https://review.openocd.org/c/openocd/+/7125
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

diff --git a/src/jtag/drivers/bcm2835gpio.c b/src/jtag/drivers/bcm2835gpio.c
index 50db87a930b4444b9d88bd75ac1377638e28057a..d02b6e4342b4347ebfc0425271aa211bc26e1566 100644 (file)
--- a/src/jtag/drivers/bcm2835gpio.c
+++ b/src/jtag/drivers/bcm2835gpio.c
@@ -51,7 +51,11 @@ static int speed_offset = 28;
 static unsigned int jtag_delay;
 
 static const struct adapter_gpio_config *adapter_gpio_config;
-static int initial_gpio_mode[ADAPTER_GPIO_IDX_NUM];
+static struct initial_gpio_state {
+       unsigned int mode;
+       unsigned int output_level;
+} initial_gpio_state[ADAPTER_GPIO_IDX_NUM];
+static uint32_t initial_drive_strength_etc;
 
 static bool is_gpio_config_valid(enum adapter_gpio_config_index idx)
 {
@@ -96,8 +100,15 @@ static void set_gpio_value(const struct adapter_gpio_config *gpio_config, int va
 
 static void restore_gpio(enum adapter_gpio_config_index idx)
 {
-       if (is_gpio_config_valid(idx))
-               SET_MODE_GPIO(adapter_gpio_config[idx].gpio_num, initial_gpio_mode[idx]);
+       if (is_gpio_config_valid(idx)) {
+               SET_MODE_GPIO(adapter_gpio_config[idx].gpio_num, initial_gpio_state[idx].mode);
+               if (initial_gpio_state[idx].mode == BCM2835_GPIO_MODE_OUTPUT) {
+                       if (initial_gpio_state[idx].output_level)
+                               GPIO_SET = 1 << adapter_gpio_config[idx].gpio_num;
+                       else
+                               GPIO_CLR = 1 << adapter_gpio_config[idx].gpio_num;
+               }
+       }
 }
 
 static void initialize_gpio(enum adapter_gpio_config_index idx)
@@ -105,10 +116,12 @@ static void initialize_gpio(enum adapter_gpio_config_index idx)
        if (!is_gpio_config_valid(idx))
                return;
 
-       initial_gpio_mode[idx] = MODE_GPIO(adapter_gpio_config[idx].gpio_num);
+       initial_gpio_state[idx].mode = MODE_GPIO(adapter_gpio_config[idx].gpio_num);
+       unsigned int shift = adapter_gpio_config[idx].gpio_num;
+       initial_gpio_state[idx].output_level = (GPIO_LEV >> shift) & 1;
        LOG_DEBUG("saved GPIO mode for %s (GPIO %d %d): %d",
                        adapter_gpio_get_name(idx), adapter_gpio_config[idx].chip_num, adapter_gpio_config[idx].gpio_num,
-                       initial_gpio_mode[idx]);
+                       initial_gpio_state[idx].mode);
 
        if (adapter_gpio_config[idx].pull != ADAPTER_GPIO_PULL_NONE) {
                LOG_WARNING("BCM2835 GPIO does not support pull-up or pull-down settings (signal %s)",
@@ -407,6 +420,7 @@ static int bcm2835gpio_init(void)
        close(dev_mem_fd);
 
        /* set 4mA drive strength, slew rate limited, hysteresis on */
+       initial_drive_strength_etc = pads_base[BCM2835_PADS_GPIO_0_27_OFFSET] & 0x1f;
        pads_base[BCM2835_PADS_GPIO_0_27_OFFSET] = 0x5a000008 + 1;
 
        /* Configure JTAG/SWD signals. Default directions and initial states are handled
@@ -478,6 +492,8 @@ static int bcm2835gpio_quit(void)
        restore_gpio(ADAPTER_GPIO_IDX_SRST);
        restore_gpio(ADAPTER_GPIO_IDX_LED);
 
+       /* Restore drive strength. MSB is password ("5A") */
+       pads_base[BCM2835_PADS_GPIO_0_27_OFFSET] = 0x5A000000 | initial_drive_strength_etc;
        bcm2835gpio_munmap();
 
        return ERROR_OK;