Message-ID: <20120322151156.GF2213@S2101-09.ap.freescale.net>
Date:	Thu, 22 Mar 2012 23:11:59 +0800
From:	Shawn Guo <shawn.guo@...aro.org>
To:	"Ying-Chun Liu (PaulLiu)" <paul.liu@...aro.org>
Cc:	rtc-linux@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linaro-dev@...ts.linaro.org,
	patches@...aro.org, Anish Trivedi <anish@...escale.com>,
	Eric Miao <eric.miao@...aro.org>,
	Anson Huang <b20788@...escale.com>,
	Alessandro Zummo <a.zummo@...ertech.it>
Subject: Re: [PATCH] rtc: add support for Freescale SNVS RTC

On Mon, Mar 19, 2012 at 09:04:29PM +0800, Ying-Chun Liu (PaulLiu) wrote:
> From: "Ying-Chun Liu (PaulLiu)" <paul.liu@...aro.org>
> 
> This adds an RTC driver for the Low Power (LP) section of SNVS.
> It hooks into the /dev/rtc interface and supports ioctl to complete RTC
> features. This driver supports device tree bindings.

Then, you need to have a document in Documentation/devicetree/bindings.

> It only uses the RTC hw in non-secure mode.
> 
> Signed-off-by: Anish Trivedi <anish@...escale.com>
> Signed-off-by: Eric Miao <eric.miao@...aro.org>
> Signed-off-by: Anson Huang <b20788@...escale.com>
> Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@...aro.org>
> Cc: Alessandro Zummo <a.zummo@...ertech.it>
> Cc: Shawn Guo <shawn.guo@...aro.org>
> ---
>  drivers/rtc/Kconfig    |   11 +
>  drivers/rtc/Makefile   |    1 +
>  drivers/rtc/rtc-snvs.c |  737 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 749 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/rtc/rtc-snvs.c
> 
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index 3a125b8..d58f4b7 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -634,6 +634,17 @@ config RTC_MXC
>  	   This driver can also be built as a module, if so, the module
>  	   will be called "rtc-mxc".
>  
> +config RTC_DRV_SNVS
> +	tristate "Freescale SNVS Real Time Clock"
> +	depends on ARCH_MXC
> +	depends on RTC_CLASS

I'm not sure this is really necessary, since this config is included
in "if RTC_CLASS".

> +	help
> +	   If you say yes here you get support for the Freescale SNVS
> +	   Low Power (LP) RTC module.
> +
> +	   This driver can also be built as a module, if so, the module
> +	   will be called "rtc-snvs".
> +
>  config RTC_DRV_BQ4802
>  	tristate "TI BQ4802"
>  	help
> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> index 6e69823..8b30686 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -93,6 +93,7 @@ obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o
>  obj-$(CONFIG_RTC_DRV_S3C)	+= rtc-s3c.o
>  obj-$(CONFIG_RTC_DRV_SA1100)	+= rtc-sa1100.o
>  obj-$(CONFIG_RTC_DRV_SH)	+= rtc-sh.o
> +obj-$(CONFIG_RTC_DRV_SNVS)	+= rtc-snvs.o
>  obj-$(CONFIG_RTC_DRV_SPEAR)	+= rtc-spear.o
>  obj-$(CONFIG_RTC_DRV_STARFIRE)	+= rtc-starfire.o
>  obj-$(CONFIG_RTC_DRV_STK17TA8)	+= rtc-stk17ta8.o
> diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
> new file mode 100644
> index 0000000..49ac8a5
> --- /dev/null
> +++ b/drivers/rtc/rtc-snvs.c
> @@ -0,0 +1,737 @@
> +/*
> + * Copyright (C) 2011 Freescale Semiconductor, Inc.
> + */
> +
> +/*
> + * 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.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> + */
> +/*
> + * Implementation based on rtc-ds1553.c
> + */
> +
> +/*!

I'm not sure "/*!" is the format for kernel-doc.  Please take a look
at Documentation/kernel-doc-nano-HOWTO.txt.

> + * @defgroup RTC Real Time Clock (RTC) Driver
> + */
> +/*!
> + * @file rtc-snvs.c
> + * @brief Secure Real Time Clock (SRTC) interface in Freescale's SNVS module
> + *
> + * This file contains Real Time Clock interface for Linux. The Freescale
> + * SNVS module's Low Power (LP) SRTC functionality is utilized in this driver,
> + * in non-secure mode.
> + *
> + * @ingroup RTC
> + */
> +
I feel above several sections of documents can just be in one multiple
line comment section.

> +#include <linux/slab.h>
> +#include <linux/delay.h>
> +#include <linux/rtc.h>
> +#include <linux/module.h>
> +#include <linux/fs.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/platform_device.h>
> +#include <linux/uaccess.h>
> +#include <linux/io.h>
> +#include <linux/sched.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +
> +/* Register definitions */
> +#define	SNVS_HPSR	0x14	/* HP Status Register */

Normally, we have one space rather than tab after "#define".

> +#define	SNVS_LPCR	0x38	/* LP Control Register */
> +#define	SNVS_LPSR	0x4C	/* LP Status Register */
> +#define	SNVS_LPSRTCMR	0x50	/* LP Secure Real Time Counter MSB Register */
> +#define	SNVS_LPSRTCLR	0x54	/* LP Secure Real Time Counter LSB Register */
> +#define	SNVS_LPTAR	0x58	/* LP Time Alarm Register */
> +#define	SNVS_LPSMCMR	0x5C	/* LP Secure Monotonic Counter MSB Register */
> +#define	SNVS_LPSMCLR	0x60	/* LP Secure Monotonic Counter LSB Register */
> +#define	SNVS_LPPGDR	0x64	/* LP Power Glitch Detector Register */
> +#define	SNVS_LPGPR	0x68	/* LP General Purpose Register */
> +
> +/* Bit Definitions */
> +#define	SNVS_HPSR_SSM_ST_MASK	0x00000F00
> +#define	SNVS_HPSR_SSM_ST_SHIFT	8
> +
> +#define	SNVS_LPCR_SRTC_ENV	(1 << 0)
> +#define	SNVS_LPCR_LPTA_EN	(1 << 1)
> +#define	SNVS_LPCR_LPWUI_EN	(1 << 3)
> +#define	SNVS_LPCR_ALL_INT_EN (SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN)

Align the indentation?

> +#define	SNVS_LPSR_LPTA		(1 << 0)
> +#define	SNVS_LPPGDR_INIT	0x41736166
> +
> +/* Other defines */
> +#define	SSM_ST_CHECK	0x9
> +#define	SSM_ST_NON_SECURE	0xB
> +#define	CNTR_TO_SECS_SH 15	/* Converts 47-bit counter to 32-bit seconds */

Ditto

> +
> +#define RTC_READ_TIME_47BIT	_IOR('p', 0x20, unsigned long long)
> +/* blocks until LPSCMR is set, returns difference */
> +#define RTC_WAIT_TIME_SET	_IOR('p', 0x21, int64_t)
> +

What are these local ioctl number exactly for?  How can user space
use these driver private numbers?

> +struct rtc_drv_data {
> +	struct rtc_device *rtc;
> +	void __iomem *ioaddr;
> +	int irq;
> +	bool irq_enable;
> +};
> +
> +static unsigned long rtc_status;
> +
> +static DEFINE_SPINLOCK(rtc_lock);
> +DECLARE_COMPLETION(snvs_completion);
> +static int64_t time_diff;
> +
> +/*!
> + * LP counter register reads should always use this function.
> + * This function reads 2 consective times from LP counter register
> + * until the 2 values match. This is to avoid reading corrupt
> + * value if the counter is in the middle of updating
> + */

If you write kernel doc for functions, please follow the format
documented in Dcumentation/kernel-doc-nano-HOWTO.txt

> +static inline u32 rtc_read_lp_counter(void __iomem *counter_reg)
> +{
> +	u64 read1, read2;
> +	u32 counter_sec;
> +
> +	do {
> +		/* MSB */
> +		read1 = readl(counter_reg);
> +		read1 <<= 32;
> +		/* LSB */
> +		read1 |= readl(counter_reg + 4);
> +
> +		/* MSB */
> +		read2 = readl(counter_reg);
> +		read2 <<= 32;
> +		/* LSB */
> +		read2 |= readl(counter_reg + 4);
> +	} while (read1 != read2);
> +
> +	/* Convert 47-bit counter to 32-bit raw second count */
> +	counter_sec = (u32) (read1 >> CNTR_TO_SECS_SH);
> +
> +	return counter_sec;
> +}
> +
It seems the function is only used to read register SNVS_LPSRTCMR, just
like that the function below is only writing register SNVS_LPSRTCLR.
Why they are using different semantics.  The above function takes
register address as argument while the following one takes snvs base
address?

> +/*!
> + * This function does write synchronization for writes to the lp srtc block.
> + * To take care of the asynchronous CKIL clock, all writes from the IP domain
> + * will be synchronized to the CKIL domain.
> + */
> +static inline void rtc_write_sync_lp(void __iomem *ioaddr)
> +{
> +	unsigned int i, count1, count2, count3;
> +
> +	/* Wait for 3 CKIL cycles */
> +	for (i = 0; i < 3; i++) {

Each loop consumes 1 CKIL cycle?

> +
> +		/* Do consective reads of LSB of counter to ensure integrity */
> +		do {
> +			count1 = readl(ioaddr + SNVS_LPSRTCLR);
> +			count2 = readl(ioaddr + SNVS_LPSRTCLR);
> +		} while (count1 != count2);
> +
> +		/* Now wait until counter value changes */
> +		do {
> +			do {
> +				count2 = readl(ioaddr + SNVS_LPSRTCLR);
> +				count3 = readl(ioaddr + SNVS_LPSRTCLR);
> +			} while (count2 != count3);
> +		} while (count3 == count1);
> +	}
> +}
> +
> +/*!
> + * This function updates the RTC alarm registers and then clears all the
> + * interrupt status bits.
> + *
> + * @param  alrm         the new alarm value to be updated in the RTC
> + *
> + * @return  0 if successful; non-zero otherwise.
> + */
> +static int rtc_update_alarm(struct device *dev, struct rtc_time *alrm)
> +{
> +	struct rtc_drv_data *pdata = dev_get_drvdata(dev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +	struct rtc_time alarm_tm, now_tm;
> +	unsigned long now, time, lp_cr;
> +	int ret;
> +
> +	now = rtc_read_lp_counter(ioaddr + SNVS_LPSRTCMR);
> +	rtc_time_to_tm(now, &now_tm);
> +
> +	alarm_tm.tm_year = now_tm.tm_year;
> +	alarm_tm.tm_mon = now_tm.tm_mon;
> +	alarm_tm.tm_mday = now_tm.tm_mday;
> +
> +	alarm_tm.tm_hour = alrm->tm_hour;
> +	alarm_tm.tm_min = alrm->tm_min;
> +	alarm_tm.tm_sec = alrm->tm_sec;
> +
> +	rtc_tm_to_time(&now_tm, &now);
> +	rtc_tm_to_time(&alarm_tm, &time);
> +
> +	if (time < now) {
> +		time += 60 * 60 * 24;
> +		rtc_time_to_tm(time, &alarm_tm);
> +	}
> +	ret = rtc_tm_to_time(&alarm_tm, &time);
> +
> +	/* Have to clear LPTA_EN before programming new alarm time in LPTAR */
> +	lp_cr = readl(ioaddr + SNVS_LPCR);
> +	writel(lp_cr & ~SNVS_LPCR_LPTA_EN, ioaddr + SNVS_LPCR);
> +	rtc_write_sync_lp(ioaddr);
> +
> +	writel(time, ioaddr + SNVS_LPTAR);
> +
> +	/* clear alarm interrupt status bit */
> +	writel(SNVS_LPSR_LPTA, ioaddr + SNVS_LPSR);
> +
> +	return ret;
> +}
> +
> +/*!
> + * This function is the RTC interrupt service routine.
> + *
> + * @param  irq          RTC IRQ number
> + * @param  dev_id       device ID which is not used
> + *
> + * @return IRQ_HANDLED as defined in the include/linux/interrupt.h file.
> + */
> +static irqreturn_t snvs_rtc_interrupt(int irq, void *dev_id)
> +{
> +	struct platform_device *pdev = dev_id;
> +	struct rtc_drv_data *pdata = platform_get_drvdata(pdev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +	u32 lp_status, lp_cr;
> +	u32 events = 0;
> +
> +	lp_status = readl(ioaddr + SNVS_LPSR);
> +	lp_cr = readl(ioaddr + SNVS_LPCR);
> +
> +	/* update irq data & counter */
> +	if (lp_status & SNVS_LPSR_LPTA) {
> +		if (lp_cr & SNVS_LPCR_LPTA_EN)
> +			events |= (RTC_AF | RTC_IRQF);
> +
> +		/* disable further lp alarm interrupts */
> +		lp_cr &= ~(SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
> +	}
> +
> +	/* Update interrupt enables */
> +	writel(lp_cr, ioaddr + SNVS_LPCR);
> +
> +	/* If no interrupts are enabled, turn off interrupts in kernel */
> +	if (((lp_cr & SNVS_LPCR_ALL_INT_EN) == 0) && (pdata->irq_enable)) {
> +		disable_irq_nosync(pdata->irq);
> +		pdata->irq_enable = false;
> +	}
> +
> +	/* clear interrupt status */
> +	writel(lp_status, ioaddr + SNVS_LPSR);
> +
> +	rtc_write_sync_lp(ioaddr);
> +	rtc_update_irq(pdata->rtc, 1, events);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +/*!
> + * This function is used to open the RTC driver.
> + *
> + * @return  0 if successful; non-zero otherwise.
> + */
> +static int snvs_rtc_open(struct device *dev)
> +{
> +	if (test_and_set_bit(1, &rtc_status))
> +		return -EBUSY;
> +
> +	return 0;
> +}
> +
> +/*!
> + * clear all interrupts and release the IRQ
> + */
> +static void snvs_rtc_release(struct device *dev)
> +{
> +	rtc_status = 0;
> +}
> +

This couple of hooks seem completely unnecessary to me, since they do
nothing but just checking reentry, which has been done by rtc core.

> +/*!
> + * This function reads the current RTC time into tm in Gregorian date.
> + *
> + * @param  tm           contains the RTC time value upon return
> + *
> + * @return  0 if successful; non-zero otherwise.
> + */
> +static int snvs_rtc_read_time(struct device *dev, struct rtc_time *tm)
> +{
> +	struct rtc_drv_data *pdata = dev_get_drvdata(dev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +
> +	rtc_time_to_tm(rtc_read_lp_counter(ioaddr + SNVS_LPSRTCMR), tm);
> +
> +	return 0;
> +}
> +
> +/*!
> + * This function sets the internal RTC time based on tm in Gregorian date.
> + *
> + * @param  tm           the time value to be set in the RTC
> + *
> + * @return  0 if successful; non-zero otherwise.
> + */
> +static int snvs_rtc_set_time(struct device *dev, struct rtc_time *tm)
> +{
> +	struct rtc_drv_data *pdata = dev_get_drvdata(dev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +	unsigned long time;
> +	int ret;
> +	u32 lp_cr;
> +	u64 old_time_47bit, new_time_47bit;
> +
> +	ret = rtc_tm_to_time(tm, &time);
> +	if (ret != 0)
> +		return ret;
> +
> +	old_time_47bit = (((u64) (readl(ioaddr + SNVS_LPSRTCMR) &
> +		((0x1 << CNTR_TO_SECS_SH) - 1)) << 32) |
> +		((u64) readl(ioaddr + SNVS_LPSRTCLR)));
> +
> +	/* Disable RTC first */
> +	lp_cr = readl(ioaddr + SNVS_LPCR) & ~SNVS_LPCR_SRTC_ENV;
> +	writel(lp_cr, ioaddr + SNVS_LPCR);
> +	while (readl(ioaddr + SNVS_LPCR) & SNVS_LPCR_SRTC_ENV)
> +		;

Don't you need proper timeout?

> +
> +	/* Write 32-bit time to 47-bit timer, leaving 15 LSBs blank */
> +	writel(time << CNTR_TO_SECS_SH, ioaddr + SNVS_LPSRTCLR);
> +	writel(time >> (32 - CNTR_TO_SECS_SH), ioaddr + SNVS_LPSRTCMR);
> +
> +	/* Enable RTC again */
> +	writel(lp_cr | SNVS_LPCR_SRTC_ENV, ioaddr + SNVS_LPCR);
> +	while (!(readl(ioaddr + SNVS_LPCR) & SNVS_LPCR_SRTC_ENV))
> +		;

Ditto

> +
> +	rtc_write_sync_lp(ioaddr);
> +
> +	new_time_47bit = (((u64) (readl(ioaddr + SNVS_LPSRTCMR) &
> +		((0x1 << CNTR_TO_SECS_SH) - 1)) << 32) |
> +		((u64) readl(ioaddr + SNVS_LPSRTCLR)));
> +
> +	time_diff = new_time_47bit - old_time_47bit;
> +
> +	/* signal all waiting threads that time changed */
> +	complete_all(&snvs_completion);
> +
> +	/* allow signalled threads to handle the time change notification */
> +	schedule();
> +
> +	/* reinitialize completion variable */
> +	INIT_COMPLETION(snvs_completion);
> +

Are you sure all these sync need to get done in driver?

> +	return 0;
> +}
> +
> +/*!
> + * This function reads the current alarm value into the passed in \b alrm
> + * argument. It updates the \b alrm's pending field value based on the whether
> + * an alarm interrupt occurs or not.
> + *
> + * @param  alrm         contains the RTC alarm value upon return
> + *
> + * @return  0 if successful; non-zero otherwise.
> + */
> +static int snvs_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct rtc_drv_data *pdata = dev_get_drvdata(dev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +
> +	rtc_time_to_tm(readl(ioaddr + SNVS_LPTAR), &alrm->time);
> +	alrm->pending =
> +	    ((readl(ioaddr + SNVS_LPSR) & SNVS_LPSR_LPTA) != 0) ? 1 : 0;
> +
> +	return 0;
> +}
> +
> +/*!
> + * This function sets the RTC alarm based on passed in alrm.
> + *
> + * @param  alrm         the alarm value to be set in the RTC
> + *
> + * @return  0 if successful; non-zero otherwise.
> + */
> +static int snvs_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct rtc_drv_data *pdata = dev_get_drvdata(dev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +	unsigned long lock_flags = 0;
> +	u32 lp_cr;
> +	int ret;
> +
> +	if (rtc_valid_tm(&alrm->time)) {
> +		if (alrm->time.tm_sec > 59 ||
> +		    alrm->time.tm_hour > 23 || alrm->time.tm_min > 59) {

Haven't all these checking been covered by rtc_valid_tm()?

> +			return -EINVAL;
> +		}
> +	}
> +
> +	spin_lock_irqsave(&rtc_lock, lock_flags);
> +
> +	ret = rtc_update_alarm(dev, &alrm->time);
> +	if (ret)
> +		goto out;
> +
> +	lp_cr = readl(ioaddr + SNVS_LPCR);
> +
> +	if (alrm->enabled)
> +		lp_cr |= (SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
> +	else
> +		lp_cr &= ~(SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
> +
> +	if (lp_cr & SNVS_LPCR_ALL_INT_EN) {
> +		if (!pdata->irq_enable) {
> +			enable_irq(pdata->irq);
> +			pdata->irq_enable = true;
> +		}
> +	} else {
> +		if (pdata->irq_enable) {
> +			disable_irq(pdata->irq);
> +			pdata->irq_enable = false;
> +		}
> +	}
> +
> +	writel(lp_cr, ioaddr + SNVS_LPCR);
> +
> +out:
> +	rtc_write_sync_lp(ioaddr);
> +	spin_unlock_irqrestore(&rtc_lock, lock_flags);
> +
> +	return ret;
> +}
> +
> +/*!
> + * This function is used to provide the content for the /proc/driver/rtc
> + * file.
> + *
> + * @param  seq  buffer to hold the information that the driver wants to write
> + *
> + * @return  The number of bytes written into the rtc file.
> + */
> +static int snvs_rtc_proc(struct device *dev, struct seq_file *seq)
> +{
> +	struct rtc_drv_data *pdata = dev_get_drvdata(dev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +
> +	seq_printf(seq, "alarm_IRQ\t: %s\n",
> +		   (((readl(ioaddr + SNVS_LPCR)) & SNVS_LPCR_LPTA_EN) !=
> +		    0) ? "yes" : "no");
> +
> +	return 0;
> +}
> +
> +static int snvs_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
> +{
> +	struct rtc_drv_data *pdata = dev_get_drvdata(dev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +	u32 lp_cr;
> +	unsigned long lock_flags = 0;
> +
> +	spin_lock_irqsave(&rtc_lock, lock_flags);
> +
> +	if (enable) {
> +		if (!pdata->irq_enable) {
> +			enable_irq(pdata->irq);
> +			pdata->irq_enable = true;
> +		}
> +		lp_cr = readl(ioaddr + SNVS_LPCR);
> +		lp_cr |= (SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
> +		writel(lp_cr, ioaddr + SNVS_LPCR);
> +	} else {
> +		lp_cr = readl(ioaddr + SNVS_LPCR);
> +		lp_cr &= ~(SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
> +		if (((lp_cr & SNVS_LPCR_ALL_INT_EN) == 0)
> +		    && (pdata->irq_enable)) {
> +			disable_irq(pdata->irq);
> +			pdata->irq_enable = false;
> +		}
> +		writel(lp_cr, ioaddr + SNVS_LPCR);
> +	}
> +
> +	rtc_write_sync_lp(ioaddr);
> +	spin_unlock_irqrestore(&rtc_lock, lock_flags);
> +
> +	return 0;
> +}
> +
> +/*!
> + * This function is used to support some ioctl calls directly.
> + * Other ioctl calls are supported indirectly through the
> + * arm/common/rtctime.c file.
> + *
> + * @param  cmd          ioctl command as defined in include/linux/rtc.h
> + * @param  arg          value for the ioctl command
> + *
> + * @return  0 if successful or negative value otherwise.
> + */
> +static int snvs_rtc_ioctl(struct device *dev, unsigned int cmd,
> +			 unsigned long arg)
> +{
> +	struct rtc_drv_data *pdata = dev_get_drvdata(dev);
> +	void __iomem *ioaddr = pdata->ioaddr;
> +	u64 time_47bit;
> +	int retVal;
> +
> +	switch (cmd) {
> +	case RTC_READ_TIME_47BIT:
> +		time_47bit = (((u64) (readl(ioaddr + SNVS_LPSRTCMR) &
> +			((0x1 << CNTR_TO_SECS_SH) - 1)) << 32) |
> +			((u64) readl(ioaddr + SNVS_LPSRTCLR)));
> +
> +		if (arg && copy_to_user((u64 *) arg, &time_47bit, sizeof(u64)))
> +			return -EFAULT;
> +
> +		return 0;
> +
> +	/* This IOCTL to be used by processes to be notified of time changes */
> +	case RTC_WAIT_TIME_SET:
> +		/* don't block without releasing mutex first */
> +		mutex_unlock(&pdata->rtc->ops_lock);
> +
> +		/* sleep till awakened by SRTC driver when LPSCMR is changed */
> +		wait_for_completion(&snvs_completion);
> +
> +		/* relock mutex because rtc_dev_ioctl will unlock again */
> +		retVal = mutex_lock_interruptible(&pdata->rtc->ops_lock);
> +
> +		/* copy the new time difference = new time - previous time
> +		 * to the user param. The difference is a signed value */
> +		if (arg && copy_to_user((int64_t *) arg, &time_diff,
> +			sizeof(int64_t)))
> +			return -EFAULT;
> +
> +		return retVal;
> +
> +	}
> +
> +	return -ENOIOCTLCMD;
> +}

I haven't completely understood this, and will need more study.

> +
> +/*!
> + * The RTC driver structure
> + */
> +static struct rtc_class_ops snvs_rtc_ops = {
> +	.open = snvs_rtc_open,
> +	.release = snvs_rtc_release,
> +	.read_time = snvs_rtc_read_time,
> +	.set_time = snvs_rtc_set_time,
> +	.read_alarm = snvs_rtc_read_alarm,
> +	.set_alarm = snvs_rtc_set_alarm,
> +	.proc = snvs_rtc_proc,
> +	.ioctl = snvs_rtc_ioctl,
> +	.alarm_irq_enable = snvs_rtc_alarm_irq_enable,
> +};
> +
> +/*! SNVS RTC Power management control */
> +static int __devinit snvs_rtc_probe(struct platform_device *pdev)
> +{
> +	struct timespec tv;
> +	struct resource *res;
> +	struct rtc_device *rtc;
> +	struct rtc_drv_data *pdata = NULL;
> +	void __iomem *ioaddr;
> +	u32 lp_cr;
> +	int ret = 0;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res)
> +		return -ENODEV;
> +
> +	ioaddr = ioremap(res->start, resource_size(res));
> +	if (!ioaddr)
> +		return -EADDRNOTAVAIL;

Use of_iomap() can save the call of platform_get_resource().

> +
> +	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
> +	if (!pdata)
> +		return -ENOMEM;
> +
> +	pdata->ioaddr = ioaddr;
> +
> +	/* Configure and enable the RTC */
> +	pdata->irq = platform_get_irq(pdev, 0);
> +	if (pdata->irq >= 0) {
> +		if (request_irq(pdata->irq, snvs_rtc_interrupt, IRQF_SHARED,
> +				pdev->name, pdev) < 0) {
> +			dev_warn(&pdev->dev, "interrupt not available.\n");
> +			pdata->irq = -1;
> +		} else {
> +			disable_irq(pdata->irq);
> +			pdata->irq_enable = false;
> +		}
> +	}
> +
> +	/* initialize glitch detect */
> +	writel(SNVS_LPPGDR_INIT, ioaddr + SNVS_LPPGDR);
> +	udelay(100);
> +
> +	/* clear lp interrupt status */
> +	writel(0xFFFFFFFF, ioaddr + SNVS_LPSR);
> +
> +	/* Enable RTC */
> +	lp_cr = readl(ioaddr + SNVS_LPCR);
> +	if ((lp_cr & SNVS_LPCR_SRTC_ENV) == 0)
> +		writel(lp_cr | SNVS_LPCR_SRTC_ENV, ioaddr + SNVS_LPCR);
> +
> +	udelay(100);
> +
> +	writel(0xFFFFFFFF, ioaddr + SNVS_LPSR);
> +	udelay(100);

All these udelay calls are necessary?

> +
> +	platform_set_drvdata(pdev, pdata);
> +
> +	rtc = rtc_device_register(pdev->name, &pdev->dev,
> +				  &snvs_rtc_ops, THIS_MODULE);
> +	if (IS_ERR(rtc)) {
> +		ret = PTR_ERR(rtc);
> +		goto err_out;
> +	}
> +
> +	pdata->rtc = rtc;
> +
> +	tv.tv_nsec = 0;
> +	tv.tv_sec = rtc_read_lp_counter(ioaddr + SNVS_LPSRTCMR);
> +
> +	/* By default, devices should wakeup if they can */
> +	/* So snvs is set as "should wakeup" as it can */
> +	device_init_wakeup(&pdev->dev, 1);
> +
> +	return ret;
> +
> +err_out:
> +	iounmap(ioaddr);
> +	if (pdata->irq >= 0)
> +		free_irq(pdata->irq, pdev);
> +
> +	return ret;
> +}
> +
> +static int __devexit snvs_rtc_remove(struct platform_device *pdev)
> +{
> +	struct rtc_drv_data *pdata = platform_get_drvdata(pdev);
> +	rtc_device_unregister(pdata->rtc);
> +	if (pdata->irq >= 0)
> +		free_irq(pdata->irq, pdev);
> +	iounmap(pdata->ioaddr);
> +
> +	return 0;
> +}
> +
> +/*!
> + * This function is called to save the system time delta relative to
> + * the SNVS RTC when enterring a low power state. This time delta is
> + * then used on resume to adjust the system time to account for time
> + * loss while suspended.
> + *
> + * @param   pdev  not used
> + * @param   state Power state to enter.
> + *
> + * @return  The function always returns 0.
> + */
> +static int snvs_rtc_suspend(struct platform_device *pdev, pm_message_t state)
> +{
> +	struct rtc_drv_data *pdata = platform_get_drvdata(pdev);
> +
> +	if (device_may_wakeup(&pdev->dev)) {
> +		enable_irq_wake(pdata->irq);
> +	} else {
> +		if (pdata->irq_enable)
> +			disable_irq(pdata->irq);
> +	}
> +
> +	return 0;
> +}
> +
> +/*!
> + * This function is called to correct the system time based on the
> + * current SNVS RTC time relative to the time delta saved during
> + * suspend.
> + *
> + * @param   pdev  not used
> + *
> + * @return  The function always returns 0.
> + */
> +static int snvs_rtc_resume(struct platform_device *pdev)
> +{
> +	struct rtc_drv_data *pdata = platform_get_drvdata(pdev);
> +
> +	if (device_may_wakeup(&pdev->dev)) {
> +		disable_irq_wake(pdata->irq);
> +	} else {
> +		if (pdata->irq_enable)
> +			enable_irq(pdata->irq);
> +	}
> +
> +	return 0;
> +}
> +

Shouldn't these 2 functions be wrapped by #ifdef CONFIG_PM?

> +static const struct of_device_id __devinitdata snvs_dt_ids[] = {
> +	{ .compatible = "fsl,snvs" },

"fsl,snvs-rtc"?

> +	{ /* sentinel */ }
> +};
> +
> +/*!
> + * Contains pointers to the power management callback functions.
> + */
> +static struct platform_driver snvs_rtc_driver = {
> +	.driver = {
> +		.name	= "snvs_rtc",
> +		.owner	= THIS_MODULE,
> +		.of_match_table = snvs_dt_ids,
> +	},
> +	.probe = snvs_rtc_probe,
> +	.remove = __exit_p(snvs_rtc_remove),
> +	.suspend = snvs_rtc_suspend,
> +	.resume = snvs_rtc_resume,
> +};
> +

...
> +/*!
> + * This function creates the /proc/driver/rtc file and registers the device RTC
> + * in the /dev/misc directory. It also reads the RTC value from external source
> + * and setup the internal RTC properly.
> + *
> + * @return  -1 if RTC is failed to initialize; 0 is successful.
> + */
> +static int __init snvs_rtc_init(void)
> +{
> +	return platform_driver_register(&snvs_rtc_driver);
> +}
> +module_init(snvs_rtc_init);
> +
> +/*!
> + * This function removes the /proc/driver/rtc file and un-registers the
> + * device RTC from the /dev/misc directory.
> + */
> +static void __exit snvs_rtc_exit(void)
> +{
> +	platform_driver_unregister(&snvs_rtc_driver);
> +}
> +module_exit(snvs_rtc_exit);

These can just be module_platform_driver(snvs_rtc_driver)?

> +
> +MODULE_AUTHOR("Anish Trivedi <anish@...escale.com>, "
> +	      "Eric Miao <eric.miao@...aro.org>, "
> +	      "Anson Huang <b20788@...escale.com>, "
> +	      "Ying-Chun Liu (PaulLiu) <paul.liu@...aro.org>");
> +MODULE_DESCRIPTION("SNVS Realtime Clock Driver (RTC)");
> +MODULE_LICENSE("GPL v2");

MODULE_ALIAS?

> -- 
> 1.7.9.1
> 

-- 
Regards,
Shawn
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