[PATCH v3 02/22] timer: imx-gpt: Add timer support for i.MX SoCs family

Giulio Benetti
2021-05-13T10:18:31Z

This timer driver uses GPT Timer (General Purpose Timer) available on
a lot of i.MX SoCs family. This driver deals with both 24Mhz oscillator
as well as peripheral clock.

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
[Giulio: added the driver's stub and handled peripheral clock prescaler
setting making driver to work correctly]
Signed-off-by: Jesse Taube <mr.bossman075@gmail.com>
[Jesse: added init, setting prescaler for 24Mhz support and enabling
timer]
---
drivers/timer/Kconfig | 7 ++
drivers/timer/Makefile | 1 +
drivers/timer/imx-gpt-timer.c | 162 ++++++++++++++++++++++++++++++++++
3 files changed, 170 insertions(+)
create mode 100644 drivers/timer/imx-gpt-timer.c

diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
index 80743a2551..ee81dfa776 100644
--- a/drivers/timer/Kconfig
+++ b/drivers/timer/Kconfig
@@ -227,4 +227,11 @@ config MCHP_PIT64B_TIMER
Select this to enable support for Microchip 64-bit periodic
interval timer.

+config IMX_GPT_TIMER
+ bool "NXP i.MX GPT timer support"
+ depends on TIMER
+ help
+ Select this to enable support for the timer found on
+ NXP i.MX devices.
+
endmenu
diff --git a/drivers/timer/Makefile b/drivers/timer/Makefile
index eb5c48cc6c..e214ba7268 100644
--- a/drivers/timer/Makefile
+++ b/drivers/timer/Makefile
@@ -25,3 +25,4 @@ obj-$(CONFIG_STM32_TIMER) += stm32_timer.o
obj-$(CONFIG_X86_TSC_TIMER) += tsc_timer.o
obj-$(CONFIG_MTK_TIMER) += mtk_timer.o
obj-$(CONFIG_MCHP_PIT64B_TIMER) += mchp-pit64b-timer.o
+obj-$(CONFIG_IMX_GPT_TIMER) += imx-gpt-timer.o
diff --git a/drivers/timer/imx-gpt-timer.c b/drivers/timer/imx-gpt-timer.c
new file mode 100644
index 0000000000..72be297754
--- /dev/null
+++ b/drivers/timer/imx-gpt-timer.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021
+ * Author(s): Giulio Benetti <giulio.benetti@benettiengineering.com>
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <fdtdec.h>
+#include <timer.h>
+#include <dm/device_compat.h>
+
+#include <asm/io.h>
+
+#define GPT_CR_EN BIT(0)
+#define GPT_CR_FRR BIT(9)
+#define GPT_CR_EN_24M BIT(10)
+#define GPT_CR_SWR BIT(15)
+
+#define GPT_PR_PRESCALER24M_MASK 0x0000F000
+#define GPT_PR_PRESCALER24M_SHIFT 12
+#define GPT_PR_PRESCALER24M_MAX (GPT_PR_PRESCALER24M_MASK >> GPT_PR_PRESCALER24M_SHIFT)
+#define GPT_PR_PRESCALER_MASK 0x00000FFF
+#define GPT_PR_PRESCALER_SHIFT 0
+#define GPT_PR_PRESCALER_MAX (GPT_PR_PRESCALER_MASK >> GPT_PR_PRESCALER_SHIFT)
+
+#define GPT_CLKSRC_IPG_CLK (1 << 6)
+#define GPT_CLKSRC_IPG_CLK_24M (5 << 6)
+
+/* If CONFIG_SYS_HZ_CLOCK not specified et's default to 3Mhz */
+#ifndef CONFIG_SYS_HZ_CLOCK
+#define CONFIG_SYS_HZ_CLOCK 3000000
+#endif
+
+struct imx_gpt_timer_regs {
+ u32 cr;
+ u32 pr;
+ u32 sr;
+ u32 ir;
+ u32 ocr1;
+ u32 ocr2;
+ u32 ocr3;
+ u32 icr1;
+ u32 icr2;
+ u32 cnt;
+};
+
+struct imx_gpt_timer_priv {
+ struct imx_gpt_timer_regs *base;
+};
+
+static u64 imx_gpt_timer_get_count(struct udevice *dev)
+{
+ struct imx_gpt_timer_priv *priv = dev_get_priv(dev);
+ struct imx_gpt_timer_regs *regs = priv->base;
+
+ return timer_conv_64(readl(&regs->cnt));
+}
+
+static int imx_gpt_setup(struct imx_gpt_timer_regs *regs, u32 rate)
+{
+ u32 prescaler = (rate / CONFIG_SYS_HZ_CLOCK) - 1;
+
+ /* Reset the timer */
+ setbits_le32(&regs->cr, GPT_CR_SWR);
+
+ /* Wait for timer to finish reset */
+ while (readl(&regs->cr) & GPT_CR_SWR)
+ ;
+
+ if (rate == 24000000UL) {
+ /* Set timer frequency if using 24M clock source */
+ if (prescaler > GPT_PR_PRESCALER24M_MAX)
+ return -EINVAL;
+
+ /* Set 24M prescaler */
+ writel((prescaler << GPT_PR_PRESCALER24M_SHIFT), &regs->pr);
+ /* Set Oscillator as clock source, enable 24M input and set gpt
+ * in free-running mode
+ */
+ writel(GPT_CLKSRC_IPG_CLK_24M | GPT_CR_EN_24M | GPT_CR_FRR, &regs->cr);
+ } else {
+ if (prescaler > GPT_PR_PRESCALER_MAX)
+ return -EINVAL;
+
+ /* Set prescaler */
+ writel((prescaler << GPT_PR_PRESCALER_SHIFT), &regs->pr);
+ /* Set Peripheral as clock source and set gpt in free-running
+ * mode
+ */
+ writel(GPT_CLKSRC_IPG_CLK | GPT_CR_FRR, &regs->cr);
+ }
+
+ /* Start timer */
+ setbits_le32(&regs->cr, GPT_CR_EN);
+
+ return 0;
+}
+
+static int imx_gpt_timer_probe(struct udevice *dev)
+{
+ struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+ struct imx_gpt_timer_priv *priv = dev_get_priv(dev);
+ struct imx_gpt_timer_regs *regs;
+ struct clk clk;
+ fdt_addr_t addr;
+ u32 clk_rate;
+ int ret;
+
+ addr = dev_read_addr(dev);
+ if (addr == FDT_ADDR_T_NONE)
+ return -EINVAL;
+
+ priv->base = (struct imx_gpt_timer_regs *)addr;
+ regs = priv->base;
+
+ ret = clk_get_by_index(dev, 0, &clk);
+ if (ret < 0)
+ return ret;
+
+ ret = clk_enable(&clk);
+ if (ret) {
+ dev_err(dev, "Failed to enable clock\n");
+ return ret;
+ }
+
+ /* Get timer clock rate */
+ clk_rate = clk_get_rate(&clk);
+ if (clk_rate <= 0) {
+ dev_err(dev, "Could not get clock rate...\n");
+ return -EINVAL;
+ }
+
+ ret = imx_gpt_setup(regs, clk_rate);
+ if (ret) {
+ dev_err(dev, "Could not setup timer\n");
+ return ret;
+ }
+
+ uc_priv->clock_rate = CONFIG_SYS_HZ_CLOCK;
+
+ return 0;
+}
+
+static const struct timer_ops imx_gpt_timer_ops = {
+ .get_count = imx_gpt_timer_get_count,
+};
+
+static const struct udevice_id imx_gpt_timer_ids[] = {
+ { .compatible = "fsl,imxrt-gpt" },
+ {}
+};
+
+U_BOOT_DRIVER(imx_gpt_timer) = {
+ .name = "imx_gpt_timer",
+ .id = UCLASS_TIMER,
+ .of_match = imx_gpt_timer_ids,
+ .priv_auto = sizeof(struct imx_gpt_timer_priv),
+ .probe = imx_gpt_timer_probe,
+ .ops = &imx_gpt_timer_ops,
+};
--
2.25.1