[PATCH 1/4] timer: imx-gpt: Add timer support for i.MX SoCs family

[Sean Anderson]

On 2/7/21 7:24 PM, Jesse Taube wrote:
> This timer driver is using GPT Timer (General Purpose Timer) available
> on almost all i.MX SoCs family.
> 
> Signed-off-by: Giulio Benetti <giulio.benetti at benettiengineering.com>
> Cc: Stefano Babic <tsbabic at denx.de>
> Cc: Giulio Benetti <giulio.benetti at benettiengineering.com>
> Cc: Jesse Taube <mr.bossman075 at gmail.com>
> ---
>   drivers/timer/Kconfig         |   7 ++
>   drivers/timer/Makefile        |   1 +
>   drivers/timer/imx-gpt-timer.c | 118 ++++++++++++++++++++++++++++++++++
>   3 files changed, 126 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..c4e8c12a42
> --- /dev/null
> +++ b/drivers/timer/imx-gpt-timer.c
> @@ -0,0 +1,118 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2020
> + * Author(s): Giulio Benetti <giulio.benetti at 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_SWR	0x00008000
> +
> +struct imx_gpt_timer_regs {

Typical style is to use offsets for this. Though I don't think it
matters.

> +	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 int imx_gpt_timer_get_count(struct udevice *dev, u64 *count)

This signature is incorrect since 8af7bb914f ("timer: Return count from
timer_ops.get_count"). Please rebase onto u-boot/master.

> +{
> +	struct imx_gpt_timer_priv *priv = dev_get_priv(dev);
> +	struct imx_gpt_timer_regs *regs = priv->base;
> +
> +	*count = readl(&regs->cnt);
> +
> +	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 prescaler;
> +	u32 rate, pr;
> +	int ret;
> +
> +	addr = dev_read_addr(dev);
> +	if (addr == FDT_ADDR_T_NONE)
> +		return -EINVAL;
> +
> +	priv->base = (struct imx_gpt_timer_regs *)addr;
> +
> +	/* TODO: Retrieve clock-source */
> +
> +	/* TODO: Retrieve prescaler */
> +
> +	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;
> +	}
> +
> +	regs = priv->base;
> +
> +	/* Reset the timer */
> +	setbits_le32(&regs->cr, GPT_CR_SWR);
> +
> +	/* Wait for timer to finish reset */
> +	while(readl(&regs->cr) & GPT_CR_SWR)
> +		;
> +
> +	/* Get timer clock rate */
> +	rate = clk_get_rate(&clk);
> +
> +	/* we set timer prescaler to obtain a 1MHz timer counter frequency */
> +//	pr = (rate / CONFIG_SYS_HZ_CLOCK) - 1;

Should this be uncommented?

> +	writel(pr, &regs->pr);
> +
> +	/* Set timer frequency to 1MHz */
> +	uc_priv->clock_rate = rate / prescaler;
> +
> +	/* start timer */
> +//	setbits_le32(&regs->cr1, CR1_CEN);

ditto

> +
> +	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" },

I believe this clock is present on other i.MX processors as well (not
just RT ones). Though those typically can use the armv7 cp15 clock.

--Sean

> +	{}
> +};
> +
> +U_BOOT_DRIVER(imx_gpt_timer) = {
> +	.name = "imx_gpt_timer",
> +	.id = UCLASS_TIMER,
> +	.of_match = imx_gpt_timer_ids,
> +	.priv_auto_alloc_size = sizeof(struct imx_gpt_timer_priv),
> +	.probe = imx_gpt_timer_probe,
> +	.ops = &imx_gpt_timer_ops,
> +};
> +
>