drivers: mcux_gpt_timer: Enabled GPT timer on MIMXRT1064 EVK

This enables the GPT timer for use as a hardware clock on the
MIMXRT1064. The timer will be disabled when builds use the GPT timer as
a counter, and the build will fall back to using the Cortex M systick as
a timer. This was tested using the kernel tickless test, to verify the
driver functions as expected.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>

boards/arm/mimxrt1064_evk/doc/index.rst

@@ -124,6 +124,8 @@ features:
 +-----------+------------+-------------------------------------+
 | SPI       | on-chip    | spi                                 |
 +-----------+------------+-------------------------------------+
+| GPT       | on-chip    | gpt                                 |
++-----------+------------+-------------------------------------+
 | DMA       | on-chip    | dma                                 |
 +-----------+------------+-------------------------------------+
 | HWINFO    | on-chip    | Unique device serial number         |
@@ -277,8 +279,8 @@ The MIMXRT1064 SoC has four pairs of pinmux/gpio controllers.
 System Clock
 ============
 
-The MIMXRT1064 SoC is configured to use the 24 MHz external oscillator on the
-board with the on-chip PLL to generate a 600 MHz core clock.
+The MIMXRT1064 SoC is configured to use the 32 KHz low frequency oscillator on
+the board as a source for the GPT timer to generate a system clock.
 
 Serial Port
 ===========

boards/arm/mimxrt1064_evk/mimxrt1064_evk.dts

@@ -266,3 +266,10 @@ zephyr_udc0: &usb1 {
 &adc1 {
 	status = "okay";
 };
+
+/* Enable GPT for use as a hardware timer. This disables Cortex Systick.
+ * to use systick, change this node from "gpt_hw_timer" to "systick"
+ */
+&gpt_hw_timer {
+	status = "okay";
+};

boards/arm/mimxrt1064_evk/mimxrt1064_evk_defconfig

@@ -9,8 +9,6 @@ CONFIG_SOC_SERIES_IMX_RT=y
 CONFIG_CONSOLE=y
 CONFIG_UART_CONSOLE=y
 CONFIG_SERIAL=y
-CONFIG_CORTEX_M_SYSTICK=y
 CONFIG_GPIO=y
-CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=600000000
 CONFIG_ARM_MPU=y
 CONFIG_HW_STACK_PROTECTION=y

soc/arm/nxp_imx/rt/Kconfig.defconfig.mimxrt1064

@@ -23,4 +23,7 @@ config IPG_DIV
 config GPIO
 	default y
 
+config SYS_CLOCK_HW_CYCLES_PER_SEC
+	default 600000000 if CORTEX_M_SYSTICK
+
 endif # SOC_MIMXRT1064

soc/arm/nxp_imx/rt/Kconfig.defconfig.series

@@ -198,6 +198,17 @@ config TEST_EXTRA_STACKSIZE
 	default 1024
 endif # MBEDTLS
 
+if MCUX_GPT_TIMER
+
+# set the tick per sec as a divider of the GPT clock source
+config SYS_CLOCK_TICKS_PER_SEC
+	default 8192
+
+config SYS_CLOCK_HW_CYCLES_PER_SEC
+	default 32786
+
+endif #MCUX_GPT_TIMER
+
 source "soc/arm/nxp_imx/rt/Kconfig.defconfig.mimxrt*"
 
 endif # SOC_SERIES_IMX_RT