Re: [PATCH v1 1/1] timer: npcm: Add driver for Nuvoton NPCM SoCs

[Jesse Taube <mr.bossman075@gmail.com>]

On 2/7/22 01:02, Stanley Chu wrote:
> This driver enables a periodic timer on NPCM SoCs and
> implements the get_count timer ops.
> 
> Signed-off-by: Stanley Chu <yschu@nuvoton.com>
> ---
>   drivers/timer/Kconfig      |   6 ++
>   drivers/timer/Makefile     |   1 +
>   drivers/timer/npcm-timer.c | 111 +++++++++++++++++++++++++++++++++++++
>   3 files changed, 118 insertions(+)
>   create mode 100644 drivers/timer/npcm-timer.c
> 
> diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
> index 8913142654..f22c46f44e 100644
> --- a/drivers/timer/Kconfig
> +++ b/drivers/timer/Kconfig
> @@ -143,6 +143,12 @@ config NOMADIK_MTU_TIMER
>   	  The MTU provides 4 decrementing free-running timers.
>   	  At the moment, only the first timer is used by the driver.
>   
> +config NPCM_TIMER
> +	bool "Nuvoton NPCM timer support"
> +	depends on TIMER
> +	help
> +	  Select this to enable a timer on Nuvoton NPCM SoCs.
> +
>   config OMAP_TIMER
>   	bool "Omap timer support"
>   	depends on TIMER
> diff --git a/drivers/timer/Makefile b/drivers/timer/Makefile
> index e2bd530eb0..39bda1ea79 100644
> --- a/drivers/timer/Makefile
> +++ b/drivers/timer/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_CADENCE_TTC_TIMER)	+= cadence-ttc.o
>   obj-$(CONFIG_DESIGNWARE_APB_TIMER)	+= dw-apb-timer.o
>   obj-$(CONFIG_MPC83XX_TIMER) += mpc83xx_timer.o
>   obj-$(CONFIG_NOMADIK_MTU_TIMER)	+= nomadik-mtu-timer.o
> +obj-$(CONFIG_NPCM_TIMER)	+= npcm-timer.o
>   obj-$(CONFIG_OMAP_TIMER)	+= omap-timer.o
>   obj-$(CONFIG_RENESAS_OSTM_TIMER) += ostm_timer.o
>   obj-$(CONFIG_RISCV_TIMER) += riscv_timer.o
> diff --git a/drivers/timer/npcm-timer.c b/drivers/timer/npcm-timer.c
> new file mode 100644
> index 0000000000..f7d95d4bfa
> --- /dev/null
> +++ b/drivers/timer/npcm-timer.c
> @@ -0,0 +1,111 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (c) 2022 Nuvoton Technology Corp.
> + */
> +
> +#include <common.h>
> +#include <clk.h>
> +#include <dm.h>
> +#include <timer.h>
> +#include <asm/io.h>
> +
> +#define NPCM_TIMER_CLOCK_RATE	1000000UL		/* 1MHz timer */
> +#define NPCM_TIMER_INPUT_RATE	25000000UL		/* Rate of input clock */
> +#define NPCM_TIMER_TDR_MASK	GENMASK(23, 0)
> +#define NPCM_TIMER_MAX_VAL	NPCM_TIMER_TDR_MASK	/* max counter value */
> +
> +/* Register offsets */
> +#define TCR0	0x0	/* Timer Control and Status Register */
> +#define TICR0	0x8	/* Timer Initial Count Register */
> +#define TDR0	0x10	/* Timer Data Register */
> +
> +/* TCR fields */
> +#define TCR_MODE_PERIODIC	BIT(27)
> +#define TCR_EN			BIT(30)
> +#define TCR_PRESCALE_25		(25 - 1)
Should this be calculated by NPCM_TIMER_INPUT_RATE/NPCM_TIMER_CLOCK_RATE

Also thanks for including me I always love the attention, but I'm not 
sure why I have been CCed in many of you recent patches is there a 
reason for this?

Thank you,
	Jesse Taube
> +
> +/*
> + * 24-bits down-counting hw timer.
> + * last_count: last hw counter value.
> + * counter: the value to be returned for get_count ops.
> + */
> +struct npcm_timer_priv {
> +	void __iomem *base;
> +	u32 last_count;
> +	u64 counter;
> +};
> +
> +static u64 npcm_timer_get_count(struct udevice *dev)
> +{
> +	struct npcm_timer_priv *priv = dev_get_priv(dev);
> +	u32 val;
> +
> +	/* The timer is couting down */
> +	val = readl(priv->base + TDR0) & NPCM_TIMER_TDR_MASK;
> +	if (val <= priv->last_count)
> +		priv->counter += priv->last_count - val;
> +	else
> +		priv->counter += priv->last_count + (NPCM_TIMER_MAX_VAL + 1 - val);
> +	priv->last_count = val;
> +
> +	return priv->counter;
> +}
> +
> +static int npcm_timer_probe(struct udevice *dev)
> +{
> +	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
> +	struct npcm_timer_priv *priv = dev_get_priv(dev);
> +	struct clk clk;
> +	int ret;
> +
> +	priv->base = dev_read_addr_ptr(dev);
> +	if (!priv->base)
> +		return -ENOENT;
> +	priv->counter = 0;
> +	priv->last_count = 0;
> +	uc_priv->clock_rate = NPCM_TIMER_CLOCK_RATE;
> +
> +	if (IS_ENABLED(CONFIG_ARCH_NPCM750)) {
> +		ret = clk_get_by_index(dev, 0, &clk);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = clk_set_rate(&clk, NPCM_TIMER_INPUT_RATE);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	/*
> +	 * Configure timer and start
> +	 * periodic mode
> +	 * input clock freq = 25Mhz
> +	 * prescale = 25
> +	 * timer clock rate = 25Mhz/25
> +	 */
> +	writel(0, priv->base + TCR0);
> +	writel(NPCM_TIMER_MAX_VAL, priv->base + TICR0);
> +	writel(TCR_EN | TCR_MODE_PERIODIC | TCR_PRESCALE_25,
> +	       priv->base + TCR0);
> +
> +	return 0;
> +}
> +
> +static const struct timer_ops npcm_timer_ops = {
> +	.get_count = npcm_timer_get_count,
> +};
> +
> +static const struct udevice_id npcm_timer_ids[] = {
> +	{ .compatible = "nuvoton,npcm845-timer" },
> +	{ .compatible = "nuvoton,npcm750-timer" },
> +	{}
> +};
> +
> +U_BOOT_DRIVER(npcm_timer) = {
> +	.name	= "npcm_timer",
> +	.id	= UCLASS_TIMER,
> +	.of_match = npcm_timer_ids,
> +	.priv_auto = sizeof(struct npcm_timer_priv),
> +	.probe = npcm_timer_probe,
> +	.ops	= &npcm_timer_ops,
> +	.flags = DM_FLAG_PRE_RELOC,
> +};