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bcm2835gpio: use maximum drive strength 

According to the docs, the default drive strength for the GPIO pads is
8mA but they're capable of 16mA. Configure GPIO 0-27 to use the maximum
(as they might be used on high enough frequency with JTAG).

Change-Id: I621737a1b0a855bb97b56ce2cc46c0e385b74f5d
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/1633
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
This commit is contained in:
Paul Fertser 2013-09-18 23:42:50 +04:00 committed by Spencer Oliver
parent 1c975fe30b
commit d4993beec4
1 changed files with 16 additions and 0 deletions
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16
src/jtag/drivers/bcm2835gpio.c
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@ -33,6 +33,9 @@
#define BCM2835_PERI_BASE 0x20000000
#define BCM2835_GPIO_BASE (BCM2835_PERI_BASE + 0x200000) /* GPIO controller */
#define BCM2835_PADS_GPIO_0_27 (BCM2835_PERI_BASE + 0x100000)
#define BCM2835_PADS_GPIO_0_27_OFFSET (0x2c / 4)
/* GPIO setup macros */
#define MODE_GPIO(g) (*(pio_base+((g)/10))>>(((g)%10)*3) & 7)
#define INP_GPIO(g) do { *(pio_base+((g)/10)) &= ~(7<<(((g)%10)*3)); } while (0)
@ -319,6 +322,19 @@ static int bcm2835gpio_init(void)
return ERROR_JTAG_INIT_FAILED;
}
static volatile uint32_t *pads_base;
pads_base = mmap(NULL, sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_WRITE,
MAP_SHARED, dev_mem_fd, BCM2835_PADS_GPIO_0_27);
if (pads_base == MAP_FAILED) {
perror("mmap");
close(dev_mem_fd);
return ERROR_JTAG_INIT_FAILED;
}
/* set 16mA drive strength */
pads_base[BCM2835_PADS_GPIO_0_27_OFFSET] = 0x5a000018 + 7;
tdo_gpio_mode = MODE_GPIO(tdo_gpio);
tdi_gpio_mode = MODE_GPIO(tdi_gpio);
tck_gpio_mode = MODE_GPIO(tck_gpio);