drivers: imx: imx_gpt: Add general purpose timer API binding

Add delay timer API so that it can be called by delay timer
layer and used as delay timer globally.

[bod: changed name from imx_delay_timer -> imx_gpt ]
Signed-off-by: Jun Nie <jun.nie@linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>

drivers/imx/timer/imx_gpt.c

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <delay_timer.h>
+#include <mmio.h>
+#include <imx_gpt.h>
+
+#define GPTCR_SWR		BIT(15)		/* Software reset */
+#define GPTCR_24MEN		BIT(10)		/* Enable 24MHz clock input */
+#define GPTCR_CLKSOURCE_OSC	(5 << 6)        /* Clock source OSC */
+#define GPTCR_CLKSOURCE_MASK	(0x7 << 6)
+#define GPTCR_TEN		1		/* Timer enable */
+
+#define GPTPR_PRESCL_24M_SHIFT 12
+
+#define SYS_COUNTER_FREQ_IN_MHZ 3
+
+#define GPTPR_TIMER_CTRL	(imx_base_addr + 0x000)
+#define GPTPR_TIMER_PRESCL	(imx_base_addr + 0x004)
+#define GPTPR_TIMER_CNTR	(imx_base_addr + 0x024)
+
+static uintptr_t imx_base_addr;
+
+uint32_t imx_get_timer_value(void)
+{
+	return ~mmio_read_32(GPTPR_TIMER_CNTR);
+}
+
+static const timer_ops_t imx_gpt_ops = {
+	.get_timer_value	= imx_get_timer_value,
+	.clk_mult		= 1,
+	.clk_div		= SYS_COUNTER_FREQ_IN_MHZ,
+};
+
+void imx_gpt_ops_init(uintptr_t base_addr)
+{
+	int val;
+
+	assert(base_addr != 0);
+
+	imx_base_addr = base_addr;
+
+	/* setup GP Timer */
+	mmio_write_32(GPTPR_TIMER_CTRL, GPTCR_SWR);
+	mmio_write_32(GPTPR_TIMER_CTRL, 0);
+
+	/* get 3MHz from 24MHz */
+	mmio_write_32(GPTPR_TIMER_PRESCL, (7 << GPTPR_PRESCL_24M_SHIFT));
+
+	val = mmio_read_32(GPTPR_TIMER_CTRL);
+	val &= ~GPTCR_CLKSOURCE_MASK;
+	val |= GPTCR_24MEN | GPTCR_CLKSOURCE_OSC | GPTCR_TEN;
+	mmio_write_32(GPTPR_TIMER_CTRL, val);
+
+	timer_init(&imx_gpt_ops);
+}

drivers/imx/timer/imx_gpt.h

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __IMX_GPT_H__
+#define __IMX_GPT_H__
+
+#include <stdint.h>
+
+void imx_gpt_ops_init(uintptr_t reg_base);
+
+#endif /* __IMX_GPT_H__ */