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References: <20190710110424.4254-1-biwen.li@nxp.com>
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From:   Li Yang <leoyang.li@nxp.com>
Date:   Wed, 10 Jul 2019 16:11:48 -0500
Message-ID: <CADRPPNR7rQqO6VHYaLn8LGAJJTiUC_+LxwjBSrj4ZkmAw=2mSw@mail.gmail.com>
Subject: Re: [v2,1/2] rtc/fsl: add FTM alarm driver as the wakeup source
To:     Biwen Li <biwen.li@nxp.com>
Cc:     a.zummo@towertech.it, alexandre.belloni@bootlin.com,
        linux-rtc@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>,
        Xiaobo Xie <xiaobo.xie@nxp.com>,
        Jiafei Pan <jiafei.pan@nxp.com>, Ran Wang <ran.wang_1@nxp.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jul 10, 2019 at 6:35 AM Biwen Li <biwen.li@nxp.com> wrote:
>
> For the paltforms including LS1012A, LS1021A, LS1028A, LS1043A,
> LS1046A, LS1088A, LS208xA that has the FlexTimer
> module, implementing alarm functions within RTC subsystem
> to wakeup the system when system going to sleep (work with RCPM driver).
>
> Signed-off-by: Biwen Li <biwen.li@nxp.com>
> ---
>
> Change in v2:
>     - remove code about setting rcpm
>
>  drivers/rtc/Kconfig             |  14 ++
>  drivers/rtc/Makefile            |   1 +
>  drivers/rtc/rtc-fsl-ftm-alarm.c | 311 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 326 insertions(+)
>  create mode 100644 drivers/rtc/rtc-fsl-ftm-alarm.c
>
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index 03b60d5..0758a08 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -1313,6 +1313,20 @@ config RTC_DRV_IMXDI
>            This driver can also be built as a module, if so, the module
>            will be called "rtc-imxdi".
>
> +config RTC_DRV_FSL_FTM_ALARM
> +       tristate "Freescale FlexTimer alarm timer"
> +       depends on ARCH_LAYERSCAPE
> +       default y
> +       help
> +          For the FlexTimer in LS1012A, LS1021A, LS1028A, LS1043A, LS1046A,
> +          LS1088A, LS208xA, we can use FTM as the wakeup source.
> +
> +          Say y here to enable FTM alarm support. The FTM alarm provides
> +          alarm functions for wakeup system from deep sleep.
> +
> +          This driver can also be built as a module, if so, the module
> +          will be called "rtc-fsl-ftm-alarm".
> +
>  config RTC_DRV_MESON
>         tristate "Amlogic Meson RTC"
>         depends on (ARM && ARCH_MESON) || COMPILE_TEST
> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> index 9d997fa..5cccb07 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -79,6 +79,7 @@ obj-$(CONFIG_RTC_DRV_HID_SENSOR_TIME) += rtc-hid-sensor-time.o
>  obj-$(CONFIG_RTC_DRV_HYM8563)  += rtc-hym8563.o
>  obj-$(CONFIG_RTC_DRV_IMXDI)    += rtc-imxdi.o
>  obj-$(CONFIG_RTC_DRV_IMX_SC)   += rtc-imx-sc.o
> +obj-$(CONFIG_RTC_DRV_FSL_FTM_ALARM)    += rtc-fsl-ftm-alarm.o
>  obj-$(CONFIG_RTC_DRV_ISL12022) += rtc-isl12022.o
>  obj-$(CONFIG_RTC_DRV_ISL12026) += rtc-isl12026.o
>  obj-$(CONFIG_RTC_DRV_ISL1208)  += rtc-isl1208.o
> diff --git a/drivers/rtc/rtc-fsl-ftm-alarm.c b/drivers/rtc/rtc-fsl-ftm-alarm.c
> new file mode 100644
> index 0000000..1836c2e
> --- /dev/null
> +++ b/drivers/rtc/rtc-fsl-ftm-alarm.c
> @@ -0,0 +1,311 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Freescale FlexTimer Module (FTM) alarm device driver.
> + *
> + * Copyright 2014 Freescale Semiconductor, Inc.
> + * Copyright 2019 NXP
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.

No need to add this with the SPDX tag.  And btw, the text here is
GPL-2.0+ instead of GPL-2.0.

> + */
> +
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/module.h>
> +#include <linux/fsl/ftm.h>
> +#include <linux/rtc.h>
> +#include <linux/time.h>
> +
> +#define FTM_SC_CLK(c)          ((c) << FTM_SC_CLK_MASK_SHIFT)
> +
> +/*
> + * Select Fixed frequency clock as clock source
> + * of FlexTimer Module
> + */
> +#define FTM_SC_CLKS_FIXED_FREQ 0x02
> +
> +#define FIXED_FREQ_CLK         32000
> +#define MAX_FREQ_DIV           (1 << FTM_SC_PS_MASK)
> +#define MAX_COUNT_VAL          0xffff
> +
> +struct ftm_rtc {
> +       struct rtc_device *rtc_dev;
> +       void __iomem *base;
> +       bool endian;

Make it big_endian to be more clear.

> +       u32 alarm_freq;
> +};
> +
> +static inline u32 rtc_readl(struct ftm_rtc *dev, u32 reg)
> +{
> +       if (dev->endian)
> +               return ioread32be(dev->base + reg); /*big endianness*/

No need to have the extra comment with new variable name.

And probably better to use "else" here to make clearer to
compiler/static analyser.

> +
> +       return ioread32(dev->base + reg);
> +}
> +
> +static inline void rtc_writel(struct ftm_rtc *dev, u32 reg, u32 val)
> +{
> +       if (dev->endian)
> +               iowrite32be(val, dev->base + reg);
> +       else
> +               iowrite32(val, dev->base + reg);
> +}
> +
> +static inline void ftm_counter_enable(struct ftm_rtc *rtc)
> +{
> +       u32 val;
> +
> +       /* select and enable counter clock source */
> +       val = rtc_readl(rtc, FTM_SC);
> +       val &= ~(FTM_SC_PS_MASK | FTM_SC_CLK_MASK);
> +       val |= (FTM_SC_PS_MASK | FTM_SC_CLK(FTM_SC_CLKS_FIXED_FREQ));
> +       rtc_writel(rtc, FTM_SC, val);
> +}
> +
> +static inline void ftm_counter_disable(struct ftm_rtc *rtc)
> +{
> +       u32 val;
> +
> +       /* disable counter clock source */
> +       val = rtc_readl(rtc, FTM_SC);
> +       val &= ~(FTM_SC_PS_MASK | FTM_SC_CLK_MASK);
> +       rtc_writel(rtc, FTM_SC, val);
> +}
> +
> +static inline void ftm_irq_acknowledge(struct ftm_rtc *rtc)
> +{
> +       unsigned int timeout = 100;
> +
> +       while ((FTM_SC_TOF & rtc_readl(rtc, FTM_SC)) && timeout--)
> +               rtc_writel(rtc, FTM_SC, rtc_readl(rtc, FTM_SC) & (~FTM_SC_TOF));

Is there a reason that we need to loop here?

> +}
> +
> +static inline void ftm_irq_enable(struct ftm_rtc *rtc)
> +{
> +       u32 val;
> +
> +       val = rtc_readl(rtc, FTM_SC);
> +       val |= FTM_SC_TOIE;
> +       rtc_writel(rtc, FTM_SC, val);
> +}
> +
> +static inline void ftm_irq_disable(struct ftm_rtc *rtc)
> +{
> +       u32 val;
> +
> +       val = rtc_readl(rtc, FTM_SC);
> +       val &= ~FTM_SC_TOIE;
> +       rtc_writel(rtc, FTM_SC, val);
> +}
> +
> +static inline void ftm_reset_counter(struct ftm_rtc *rtc)
> +{
> +       /*
> +        * The CNT register contains the FTM counter value.
> +        * Reset clears the CNT register. Writing any value to COUNT
> +        * updates the counter with its initial value, CNTIN.
> +        */
> +       rtc_writel(rtc, FTM_CNT, 0x00);
> +}
> +
> +static void ftm_clean_alarm(struct ftm_rtc *rtc)
> +{
> +       ftm_counter_disable(rtc);
> +
> +       rtc_writel(rtc, FTM_CNTIN, 0x00);
> +       rtc_writel(rtc, FTM_MOD, ~0U);
> +
> +       ftm_reset_counter(rtc);
> +}
> +
> +static irqreturn_t ftm_rtc_alarm_interrupt(int irq, void *dev)
> +{
> +       struct ftm_rtc *rtc = dev;
> +
> +       ftm_irq_acknowledge(rtc);
> +       ftm_irq_disable(rtc);
> +       ftm_clean_alarm(rtc);
> +
> +       return IRQ_HANDLED;
> +}
> +
> +static int ftm_rtc_alarm_irq_enable(struct device *dev,
> +               unsigned int enabled)
> +{
> +       struct ftm_rtc *rtc = dev_get_drvdata(dev);
> +
> +       if (enabled)
> +               ftm_irq_enable(rtc);
> +       else
> +               ftm_irq_disable(rtc);
> +
> +       return 0;
> +}
> +
> +/*
> + * Note:
> + *     The function is not really getting time from the RTC
> + *     since FlexTimer is not a RTC device, but we need to
> + *     get time to setup alarm, so we are using system time
> + *     for now.
> + */
> +static int ftm_rtc_read_time(struct device *dev, struct rtc_time *tm)
> +{
> +       struct timespec64 ts64;
> +       unsigned long local_time;
> +
> +       ktime_get_real_ts64(&ts64);
> +       local_time = (unsigned long)(ts64.tv_sec - (sys_tz.tz_minuteswest * 60));
> +
> +       rtc_time_to_tm(local_time, tm);
> +
> +       return 0;
> +}

New line here.

> +static int ftm_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
> +{
> +       return 0;

Why we cannot read the alarm time?

> +}
> +
> +/*250Hz, 65536 / 250 = 262 second max*/

Can you make the comment more readable?

> +static int ftm_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
> +{
> +       struct rtc_time tm;
> +       unsigned long now, alm_time, cycle;
> +       struct ftm_rtc *rtc = dev_get_drvdata(dev);
> +
> +       ftm_rtc_read_time(dev, &tm);
> +       rtc_tm_to_time(&tm, &now);
> +       rtc_tm_to_time(&alm->time, &alm_time);
> +
> +       ftm_clean_alarm(rtc);
> +       cycle = (alm_time - now) * rtc->alarm_freq;
> +       if (cycle > MAX_COUNT_VAL) {
> +               pr_err("Out of alarm range.\n");

Better to tell the users what the range is than letting them try out.

> +               return -EINVAL;
> +       }
> +
> +       ftm_irq_disable(rtc);
> +
> +       /*
> +        * The counter increments until the value of MOD is reached,
> +        * at which point the counter is reloaded with the value of CNTIN.
> +        * The TOF (the overflow flag) bit is set when the FTM counter
> +        * changes from MOD to CNTIN. So we should using the cycle - 1.
> +        */
> +       rtc_writel(rtc, FTM_MOD, cycle - 1);
> +
> +       ftm_counter_enable(rtc);
> +       ftm_irq_enable(rtc);
> +
> +       return 0;
> +
> +}
> +
> +static const struct rtc_class_ops ftm_rtc_ops = {
> +       .read_time              = ftm_rtc_read_time,
> +       .read_alarm             = ftm_rtc_read_alarm,
> +       .set_alarm              = ftm_rtc_set_alarm,
> +       .alarm_irq_enable       = ftm_rtc_alarm_irq_enable,
> +};

New line is needed.

> +static int ftm_rtc_probe(struct platform_device *pdev)
> +{
> +       struct device_node *np = pdev->dev.of_node;
> +       struct resource *r;
> +       int irq;
> +       int ret;
> +       struct ftm_rtc *rtc;
> +
> +       rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
> +       if (unlikely(!rtc)) {
> +               pr_err("ftm: cannot alloc memery for rtc\n");
> +               return -ENOMEM;
> +       }
> +
> +

No two new lines.

> +       platform_set_drvdata(pdev, rtc);
> +
> +       r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       if (!r) {
> +               pr_err("ftm: cannot get resource for rtc\n");
> +               return -ENODEV;
> +       }
> +
> +       rtc->base = devm_ioremap_resource(&pdev->dev, r);
> +       if (IS_ERR(rtc->base)) {
> +               pr_err("ftm: cannot ioremap resource for rtc\n");
> +               return PTR_ERR(rtc->base);
> +       }
> +
> +       irq = irq_of_parse_and_map(np, 0);
> +       if (irq <= 0) {
> +               pr_err("ftm: unable to get IRQ from DT, %d\n", irq);
> +               return -EINVAL;
> +       }
> +
> +       rtc->endian = of_property_read_bool(np, "big-endian");
> +
> +       ret = devm_request_irq(&pdev->dev, irq, ftm_rtc_alarm_interrupt,
> +                              IRQF_NO_SUSPEND, dev_name(&pdev->dev), rtc);
> +       if (ret < 0) {
> +               dev_err(&pdev->dev, "failed to request irq\n");
> +               return ret;
> +       }
> +
> +       rtc->alarm_freq = (u32)FIXED_FREQ_CLK / (u32)MAX_FREQ_DIV;
> +
> +       ftm_clean_alarm(rtc);
> +
> +       device_init_wakeup(&pdev->dev, true);
> +       rtc->rtc_dev = devm_rtc_device_register(&pdev->dev, "ftm-alarm",
> +                                                       &ftm_rtc_ops,
> +                                                       THIS_MODULE);
> +       if (IS_ERR(rtc->rtc_dev)) {
> +               dev_err(&pdev->dev, "can't register rtc device\n");
> +               return PTR_ERR(rtc->rtc_dev);
> +       }
> +       return ret;
> +}
> +
> +static const struct of_device_id ftm_rtc_match[] = {
> +       { .compatible = "fsl,ftm-alarm", },
> +       { .compatible = "fsl,ls1012a-ftm-alarm", },
> +       { .compatible = "fsl,ls1021a-ftm-alarm", },
> +       { .compatible = "fsl,ls1043a-ftm-alarm", },
> +       { .compatible = "fsl,ls1046a-ftm-alarm", },
> +       { .compatible = "fsl,ls1088a-ftm-alarm", },
> +       { .compatible = "fsl,ls208xa-ftm-alarm", },
> +       { .compatible = "fsl,ls1028a-ftm-alarm", },
> +       { },
> +};
> +
> +static struct platform_driver ftm_rtc_driver = {
> +       .probe          = ftm_rtc_probe,
> +       .driver         = {
> +               .name   = "ftm-alarm",
> +               .of_match_table = ftm_rtc_match,
> +       },
> +};
> +
> +static int __init ftm_alarm_init(void)
> +{
> +       return platform_driver_register(&ftm_rtc_driver);
> +}
> +
> +/***************

This is not standard Linux multiline comment style.

> + *Ensure that the driver is initialized after
> + *any real rtc driver

Can you explain why it has to be initialized later than other rtc drivers?

> + */
> +device_initcall_sync(ftm_alarm_init);
> +
> +MODULE_DESCRIPTION("NXP/Freescale FlexTimer alarm driver");
> +MODULE_AUTHOR("Biwen Li <biwen.li@nxp.com>");
> +MODULE_LICENSE("GPL");
> --
> 2.7.4
>