Date:	Sat, 19 Jun 2010 15:53:18 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Wan ZongShun <mcuos.com@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Vasut <marek.vasut@...il.com>,
	Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
	linux-kernel@...r.kernel.org,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Paul Gortmaker <p_gortmaker@...oo.com>,
	rtc-linux@...glegroups.com
Subject: Re: [PATCH v2 15/26] RTC: Add JZ4740 RTC driver

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Wan ZongShun wrote:
> Hi Lars-Peter,
>
>
>> Hi
>>
>> Marek Vasut wrote:
>>> Dne So 19. června 2010 07:08:20 Lars-Peter Clausen napsal(a):
>>> 
>>>> This patch adds support for the RTC unit on JZ4740 SoCs.
>>>>
>>>> Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
>>>> Cc: Alessandro Zummo <a.zummo@...ertech.it>
>>>> Cc: Paul Gortmaker <p_gortmaker@...oo.com>
>>>> Cc: Wan ZongShun <mcuos.com@...il.com>
>>>> Cc: Marek Vasut <marek.vasut@...il.com>
>>>> Cc: rtc-linux@...glegroups.com
>>>>
>>>> ---
>>>> Changes since v1
>>>> - Use dev_get_drvdata directly instead of wrapping it in dev_to_rtc
>>>> - Add common implementation for jz4740_rtc_{alarm,update}_irq_enable
>>>> - Check whether rtc structure could be allocated
>>>> - Fix deadlocks which could occur if the HW was broken
>>>> ---
>>>>  drivers/rtc/Kconfig      |   11 ++
>>>>  drivers/rtc/Makefile     |    1 +
>>>>  drivers/rtc/rtc-jz4740.c |  341
>>>> ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 353
>>>> insertions(+), 0 deletions(-)
>>>>  create mode 100644 drivers/rtc/rtc-jz4740.c
>>>>
>>>> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
>>>> index 10ba12c..d0ed7e6 100644
>>>> --- a/drivers/rtc/Kconfig
>>>> +++ b/drivers/rtc/Kconfig
>>>> @@ -905,4 +905,15 @@ config RTC_DRV_MPC5121
>>>>        This driver can also be built as a module. If so, the module
>>>>        will be called rtc-mpc5121.
>>>>
>>>> +config RTC_DRV_JZ4740
>>>> +    tristate "Ingenic JZ4740 SoC"
>>>> +    depends on RTC_CLASS
>>>> +    depends on MACH_JZ4740
>>>> +    help
>>>> +      If you say yes here you get support for the Ingenic JZ4740
>>>> SoC RTC
>>>> +      controller.
>>>> +
>>>> +      This driver can also be buillt as a module. If so, the module
>>>> +      will be called rtc-jz4740.
>>>> +
>>>>  endif # RTC_CLASS
>>>> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
>>>> index 5adbba7..fedf9bb 100644
>>>> --- a/drivers/rtc/Makefile
>>>> +++ b/drivers/rtc/Makefile
>>>> @@ -47,6 +47,7 @@ obj-$(CONFIG_RTC_DRV_EP93XX)    += rtc-ep93xx.o
>>>>  obj-$(CONFIG_RTC_DRV_FM3130)    += rtc-fm3130.o
>>>>  obj-$(CONFIG_RTC_DRV_GENERIC)    += rtc-generic.o
>>>>  obj-$(CONFIG_RTC_DRV_ISL1208)    += rtc-isl1208.o
>>>> +obj-$(CONFIG_RTC_DRV_JZ4740)    += rtc-jz4740.o
>>>>  obj-$(CONFIG_RTC_DRV_M41T80)    += rtc-m41t80.o
>>>>  obj-$(CONFIG_RTC_DRV_M41T94)    += rtc-m41t94.o
>>>>  obj-$(CONFIG_RTC_DRV_M48T35)    += rtc-m48t35.o
>>>> diff --git a/drivers/rtc/rtc-jz4740.c b/drivers/rtc/rtc-jz4740.c
>>>> new file mode 100644
>>>> index 0000000..720afb2
>>>> --- /dev/null
>>>> +++ b/drivers/rtc/rtc-jz4740.c
>>>> @@ -0,0 +1,341 @@
>>>> +/*
>>>> + *  Copyright (C) 2009-2010, Lars-Peter Clausen <lars@...afoo.de>
>>>> + *    JZ4740 SoC RTC driver
>>>> + *
>>>> + *  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.
>>>> + *
>>>> + *  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., + *  675 Mass Ave, Cambridge, MA 02139, USA.
>>>> + *
>>>> + */
>>>> +
>>>> +#include <linux/kernel.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/rtc.h>
>>>> +#include <linux/slab.h>
>>>> +#include <linux/spinlock.h>
>>>> +
>>>> +#define JZ_REG_RTC_CTRL        0x00
>>>> +#define JZ_REG_RTC_SEC        0x04
>>>> +#define JZ_REG_RTC_SEC_ALARM    0x08
>>>> +#define JZ_REG_RTC_REGULATOR    0x0C
>>>> +#define JZ_REG_RTC_HIBERNATE    0x20
>>>> +#define JZ_REG_RTC_SCRATCHPAD    0x34
>>>> +
>>>> +#define JZ_RTC_CTRL_WRDY    BIT(7)
>>>> +#define JZ_RTC_CTRL_1HZ        BIT(6)
>>>> +#define JZ_RTC_CTRL_1HZ_IRQ    BIT(5)
>>>> +#define JZ_RTC_CTRL_AF        BIT(4)
>>>> +#define JZ_RTC_CTRL_AF_IRQ    BIT(3)
>>>> +#define JZ_RTC_CTRL_AE        BIT(2)
>>>> +#define JZ_RTC_CTRL_ENABLE    BIT(0)
>>>> +
>>>> +struct jz4740_rtc {
>>>> +    struct resource *mem;
>>>> +    void __iomem *base;
>>>> +
>>>> +    struct rtc_device *rtc;
>>>> +
>>>> +    unsigned int irq;
>>>> +
>>>> +    spinlock_t lock;
>>>> +};
>>>> +
>>>> +static inline uint32_t jz4740_rtc_reg_read(struct jz4740_rtc
>>>> *rtc, size_t
>>>> reg) +{
>>>> +    return readl(rtc->base + reg);
>>>> +}
>>>> +
>>>> +static inline void jz4740_rtc_wait_write_ready(struct jz4740_rtc
>>>> *rtc)
>>>> +{
>>>> +    uint32_t ctrl;
>>>> +    int timeout = 1000;
>>>> +
>>>> +    do {
>>>> +        ctrl = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_CTRL);
>>>> +    } while (!(ctrl & JZ_RTC_CTRL_WRDY) && --timeout);
>>>>    
>>> if (!timeout) {
>>>     scream_and_die_in_pain();
>>>     dev_err("I died");
>>> ... or something like that ... what if it times out, in this
>>> implementation, noone will know this failed.
>>>
>>> I haven't looked through the whole source code, but can't this be
>>> wrapped into the reg_write() ?
>>> }
>>>  
>> Well IF it will ever die, you'll notice cause your rtc clock won't
>> work
>> anymore.
>>
>> It could be wrapped into reg_write, but there is a different
>> version of
>> the SoC with the only difference of the RTC unit being that a
>> different
>> mechanism is used determine whether it is ok to write or not. So it
>> makes sense to keep it seperate.
>>>> +}
>>>> +
>>>> +static inline void jz4740_rtc_reg_write(struct jz4740_rtc *rtc,
>>>> size_t
>>>> reg, +    uint32_t val)
>>>> +{
>>>> +    jz4740_rtc_wait_write_ready(rtc);
>>>> +    writel(val, rtc->base + reg);
>>>> +}
>>>> +
>>>> +static void jz4740_rtc_ctrl_set_bits(struct jz4740_rtc *rtc,
>>>> uint32_t
>>>> mask, +    uint32_t val)
>>>> +{
>>>> +    unsigned long flags;
>>>> +    uint32_t ctrl;
>>>> +
>>>> +    spin_lock_irqsave(&rtc->lock, flags);
>>>>    
>>> Can't we use local_irq_save()/local_irq_restore() ?
>>>  
>> Why would that be preferable? In the non-debug, non-rt case this will
>> expand to local_irq_{save,restore} anyway, but you'll lose the
>> semantics
>> of an lock.
>
> Anyway,spin_lock_irqsave is most universal and secure lock function,
> it can
> apply to smp or single cpu, it can be ok here.
>
>
>>> 
>>>> +
>>>> +    ctrl = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_CTRL);
>>>> +
>>>> +    /* Don't clear interrupt flags by accident */
>>>> +    ctrl |= JZ_RTC_CTRL_1HZ | JZ_RTC_CTRL_AF;
>>>> +
>>>> +    ctrl &= ~mask;
>>>> +    ctrl |= val;
>>>> +
>>>> +    jz4740_rtc_reg_write(rtc, JZ_REG_RTC_CTRL, ctrl);
>>>> +
>>>> +    spin_unlock_irqrestore(&rtc->lock, flags);
>>>> +}
>>>> +
>>>> +static int jz4740_rtc_read_time(struct device *dev, struct
>>>> rtc_time *time)
>>>> +{
>>>> +    struct jz4740_rtc *rtc = dev_get_drvdata(dev);
>>>> +    uint32_t secs, secs2;
>>>> +    int timeout = 5;
>>>> +
>>>> +    /* If the seconds register is read while it is updated, it
>>>> can contain a
>>>> +     * bogus value. This can be avoided by making sure that two
>>>> consecutive
>>>> +     * reads have the same value.
>>>> +     */
>>>> +    secs = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SEC);
>>>> +    secs2 = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SEC);
>>>> +
>>>> +    while (secs != secs2 && --timeout) {
>>>> +        secs = secs2;
>>>> +        secs2 = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SEC);
>>>> +    }
>>>> +
>>>> +    if (timeout == 0)
>>>> +        return -EIO;
>>>> +
>>>> +    rtc_time_to_tm(secs, time);
>>>> +
>>>> +    return rtc_valid_tm(time);
>>>> +}
>>>> +
>>>> +static int jz4740_rtc_set_mmss(struct device *dev, unsigned long
>>>> secs)
>>>> +{
>>>> +    struct jz4740_rtc *rtc = dev_get_drvdata(dev);
>>>> +
>>>> +    if ((uint32_t)secs != secs)
>>>> +        return -EINVAL;
>>>>    
>>> Is the typecast here necessary ?
>>>  
>> Strictly speaking not.
>>> 
>>>> +
>>>> +    jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SEC, secs);
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static int jz4740_rtc_read_alarm(struct device *dev, struct
>>>> rtc_wkalrm
>>>> *alrm) +{
>>>> +    struct jz4740_rtc *rtc = dev_get_drvdata(dev);
>>>> +    uint32_t secs;
>>>> +    uint32_t ctrl;
>>>> +
>>>> +    secs = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SEC_ALARM);
>>>> +
>>>> +    ctrl = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_CTRL);
>>>> +
>>>> +    alrm->enabled = !!(ctrl & JZ_RTC_CTRL_AE);
>>>> +    alrm->pending = !!(ctrl & JZ_RTC_CTRL_AF);
>>>> +
>>>>    
>>> Is the double negation (!!) here necessary ?
>>>
>>>  
>> To quote rtc.h "/* 0 = alarm disabled, 1 = alarm enabled */", so yes.
>
> You are right, but it is not true reason.
>
> Please keep (!!) here, to make sure 'enabled' and 'pending'
> to be '0' or '1' is good habit, since they are 'unsigned char'
> variables.
>
> Thanks!
>
>>>> +    rtc_time_to_tm(secs, &alrm->time);
>>>> +
>>>> +    return rtc_valid_tm(&alrm->time);
>>>> +}
>>>> +
>>>> +static int jz4740_rtc_set_alarm(struct device *dev, struct
>>>> rtc_wkalrm
>>>> *alrm) +{
>>>> +    struct jz4740_rtc *rtc = dev_get_drvdata(dev);
>>>> +    unsigned long secs;
>>>> +
>>>> +    rtc_tm_to_time(&alrm->time, &secs);
>>>> +
>>>> +    if ((uint32_t)secs != secs)
>>>> +        return -EINVAL;
>>>>    
>>> DTTO above
>>>
>>> 
>>>> +
>>>> +    jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SEC_ALARM,
>>>> (uint32_t)secs);
>>>>    
>>> DTTO
>>>
>>> 
>>>> +    jz4740_rtc_ctrl_set_bits(rtc, JZ_RTC_CTRL_AE,
>>>> +                    alrm->enabled ? JZ_RTC_CTRL_AE : 0);
>>>>    
>>> Possibly the double negation above wasn't necessary
>>>
>>> 
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static inline int jz4740_irq_enable(struct device *dev, int irq,
>>>> +    unsigned int enable)
>>>> +{
>>>> +    struct jz4740_rtc *rtc = dev_get_drvdata(dev);
>>>> +    jz4740_rtc_ctrl_set_bits(rtc, irq, enable ? irq : 0);
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static int jz4740_rtc_update_irq_enable(struct device *dev,
>>>> unsigned int
>>>> enable) +{
>>>> +    return jz4740_irq_enable(dev, JZ_RTC_CTRL_1HZ_IRQ, enable);
>>>> +}
>>>> +
>>>> +static int jz4740_rtc_alarm_irq_enable(struct device *dev,
>>>> unsigned int
>>>> enable) +{
>>>> +    return jz4740_irq_enable(dev, JZ_RTC_CTRL_AF_IRQ, enable);
>>>> +}
>>>> +
>>>> +static struct rtc_class_ops jz4740_rtc_ops = {
>>>> +    .read_time    = jz4740_rtc_read_time,
>>>> +    .set_mmss    = jz4740_rtc_set_mmss,
>>>> +    .read_alarm    = jz4740_rtc_read_alarm,
>>>> +    .set_alarm    = jz4740_rtc_set_alarm,
>>>> +    .update_irq_enable = jz4740_rtc_update_irq_enable,
>>>> +    .alarm_irq_enable = jz4740_rtc_alarm_irq_enable,
>>>> +};
>>>> +
>>>> +static irqreturn_t jz4740_rtc_irq(int irq, void *data)
>>>> +{
>>>> +    struct jz4740_rtc *rtc = data;
>>>> +    uint32_t ctrl;
>>>> +    unsigned long events = 0;
>>>> +    ctrl = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_CTRL);
>>>> +
>>>> +    if (ctrl & JZ_RTC_CTRL_1HZ)
>>>> +        events |= (RTC_UF | RTC_IRQF);
>>>> +
>>>> +    if (ctrl & JZ_RTC_CTRL_AF)
>>>> +        events |= (RTC_AF | RTC_IRQF);
>>>> +
>>>> +    rtc_update_irq(rtc->rtc, 1, events);
>>>> +
>>>> +    jz4740_rtc_ctrl_set_bits(rtc, JZ_RTC_CTRL_1HZ |
>>>> JZ_RTC_CTRL_AF, 0);
>>>> +
>>>> +    return IRQ_HANDLED;
>>>> +}
>>>> +
>>>> +void jz4740_rtc_poweroff(struct device *dev)
>>>> +{
>>>> +    struct jz4740_rtc *rtc = dev_get_drvdata(dev);
>>>> +    jz4740_rtc_reg_write(rtc, JZ_REG_RTC_HIBERNATE, 1);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(jz4740_rtc_poweroff);
>>>> +
>>>> +static int __devinit jz4740_rtc_probe(struct platform_device *pdev)
>>>> +{
>>>> +    int ret;
>>>> +    struct jz4740_rtc *rtc;
>>>> +    uint32_t scratchpad;
>>>> +
>>>> +    rtc = kmalloc(sizeof(*rtc), GFP_KERNEL);
>
> Please use kzalloc or kmalloc plus memset, but you forget to add
> memset,
> I prefer kzalloc, of course, you can use latter.
>
All fields of the struct are initialized in probe function, so kzalloc
is unnecessary overhead(small though).
>>>> +    if (!rtc)
>>>> +        return -ENOMEM;
>>>> +
>>>> +    rtc->irq = platform_get_irq(pdev, 0);
>>>> +    if (rtc->irq < 0) {
>>>> +        ret = -ENOENT;
>>>> +        dev_err(&pdev->dev, "Failed to get platform irq\n");
>>>> +        goto err_free;
>>>> +    }
>>>> +
>>>> +    rtc->mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>> +    if (!rtc->mem) {
>>>> +        ret = -ENOENT;
>>>> +        dev_err(&pdev->dev, "Failed to get platform mmio
>>>> memory\n");
>>>> +        goto err_free;
>>>> +    }
>>>> +
>>>> +    rtc->mem = request_mem_region(rtc->mem->start,
>>>> resource_size(rtc->mem),
>>>> +                    pdev->name);
>>>> +    if (!rtc->mem) {
>>>> +        ret = -EBUSY;
>>>> +        dev_err(&pdev->dev, "Failed to request mmio memory
>>>> region\n");
>>>> +        goto err_free;
>>>> +    }
>>>> +
>>>> +    rtc->base = ioremap_nocache(rtc->mem->start,
>>>> resource_size(rtc->mem));
>>>> +    if (!rtc->base) {
>>>> +        ret = -EBUSY;
>>>> +        dev_err(&pdev->dev, "Failed to ioremap mmio memory\n");
>>>> +        goto err_release_mem_region;
>>>> +    }
>>>> +
>>>> +    spin_lock_init(&rtc->lock);
>>>> +
>>>> +    platform_set_drvdata(pdev, rtc);
>>>>    
>>> dev_set_drvdata()?
>>>
>>>  
>> No.
>>>> +
>>>> +    rtc->rtc = rtc_device_register(pdev->name, &pdev->dev,
>>>> &jz4740_rtc_ops,
>>>> +                    THIS_MODULE);
>>>> +    if (IS_ERR(rtc->rtc)) {
>>>> +        ret = PTR_ERR(rtc->rtc);
>>>> +        dev_err(&pdev->dev, "Failed to register rtc device:
>>>> %d\n", ret);
>>>> +        goto err_iounmap;
>>>> +    }
>>>> +
>>>> +    ret = request_irq(rtc->irq, jz4740_rtc_irq, 0,
>>>> +                pdev->name, rtc);
> In fact, I prefer you can use this IRQ flags, such as IRQF_DISABLED,
> IRQF_SHARED.
IRQF_DISABLED is deprecated and IRQF_SHARED doesn't make any sense
here. In fact not requesting with IRQF_SHARED might help to spot
errors if another driver requested the IRQ by accident (Or this driver
requested the wrong irq).
>
>>>> +    if (ret) {
>>>> +        dev_err(&pdev->dev, "Failed to request rtc irq: %d\n",
>>>> ret);
>>>> +        goto err_unregister_rtc;
>>>> +    }
>>>> +
>>>> +    scratchpad = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD);
>>>> +    if (scratchpad != 0x12345678) {
>>>> +        jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD,
>>>> 0x12345678);
>>>> +        jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SEC, 0);
>>>> +    }
>>>> +
>>>> +    return 0;
>>>> +
>>>> +err_unregister_rtc:
>>>> +    rtc_device_unregister(rtc->rtc);
>>>> +err_iounmap:
>>>> +    platform_set_drvdata(pdev, NULL);
>>>> +    iounmap(rtc->base);
>>>> +err_release_mem_region:
>>>> +    release_mem_region(rtc->mem->start, resource_size(rtc->mem));
>>>> +err_free:
>>>> +    kfree(rtc);
>>>> +
>>>> +    return ret;
>>>> +}
>>>> +
>>>> +static int __devexit jz4740_rtc_remove(struct platform_device
>>>> *pdev)
>>>> +{
>>>> +    struct jz4740_rtc *rtc = platform_get_drvdata(pdev);
>>>>    
>>> dev_get_drvdata();
>>>
>>> 
>>>> +
>>>> +    free_irq(rtc->irq, rtc);
>>>> +
>>>> +    rtc_device_unregister(rtc->rtc);
>>>> +
>>>> +    iounmap(rtc->base);
>>>> +    release_mem_region(rtc->mem->start, resource_size(rtc->mem));
>>>> +
>>>> +    kfree(rtc);
>>>> +
>>>> +    platform_set_drvdata(pdev, NULL);
>>>>    
>>> DTTO
>>>
>>> 
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +struct platform_driver jz4740_rtc_driver = {
>>>> +    .probe = jz4740_rtc_probe,
>>>> +    .remove = __devexit_p(jz4740_rtc_remove),
>>>> +    .driver = {
>>>> +        .name = "jz4740-rtc",
>>>> +        .owner = THIS_MODULE,
>>>> +    },
>>>> +};
>>>> +
>>>> +static int __init jz4740_rtc_init(void)
>>>> +{
>>>> +    return platform_driver_register(&jz4740_rtc_driver);
>>>> +}
>>>> +module_init(jz4740_rtc_init);
>>>> +
>>>> +static void __exit jz4740_rtc_exit(void)
>>>> +{
>>>> +    platform_driver_unregister(&jz4740_rtc_driver);
>>>> +}
>>>> +module_exit(jz4740_rtc_exit);
>>>> +
>>>> +MODULE_AUTHOR("Lars-Peter Clausen <lars@...afoo.de>");
>>>> +MODULE_LICENSE("GPL");
>>>> +MODULE_DESCRIPTION("RTC driver for the JZ4740 SoC\n");
>>>> +MODULE_ALIAS("platform:jz4740-rtc");
>>>>    
>>> Cheers
>>>  
Thanks for reviewing
- - Lars


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