Date:	Sat, 19 Jun 2010 15:05:18 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Marek Vasut <marek.vasut@...il.com>
CC:	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>,
	Wan ZongShun <mcuos.com@...il.com>, rtc-linux@...glegroups.com
Subject: Re: [PATCH v2 15/26] RTC: Add JZ4740 RTC driver

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.
>   
>> +
>> +	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.
>> +	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);
>> +	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);
>> +	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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