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Date: Sun, 13 Jun 2010 19:44:56 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Wan ZongShun <mcuos.com@...il.com>
Cc: rtc-linux@...glegroups.com,
Andrew Morton <akpm@...ux-foundation.org>,
Alessandro Zummo <a.zummo@...ertech.it>,
"Linux/m68k" <linux-m68k@...r.kernel.org>,
Linux Kernel Development <linux-kernel@...r.kernel.org>
Subject: Re: [rtc-linux] [PATCH] rtc: rp5c01 - Add NVRAM support
On Sun, Jun 13, 2010 at 15:41, Wan ZongShun <mcuos.com@...il.com> wrote:
> Minior comment below:
>
> 2010/6/13 Geert Uytterhoeven <geert@...ux-m68k.org>:
>> The Ricoh RP5C01 RTC contains 26 x 4 bits of NVRAM.
>> Provide access to it via a sysfs "nvram" attribute file.
>>
>> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>> --
>> Question: Is a spinlock in priv the right kind of locking?
>> Should I use e.g. rtc-device.ops_lock instead?
>
> Firstly, this 'Question' text should not put here, please put all
> texts in front of '---'.
I explicitly put it there, as the question was meant for the reviewers only,
and I don't want it to be part of the final checkin comment.
> Secondly, You can not use rtc-device.ops_lock here, if so, it would
> arouse dead lock,
> before the ' rp5c01_read_time()' was called by RTC subsystem upper
> API, rtc-device.ops_lock
> has been required sucessfully, If continue to require the
> rtc-device.ops_lock in ' rp5c01_read_time()',
> the 'lock' will cannot be get, dead lock occurs.
Sorry, my question was not that correctly formulated...
I meant whether it's better to take rtc_device.ops_lock in the nvram
access functions
to synchronize with the RTC access functions (which already take that mutex),
instead of adding a spinlock to priv.
Thanks for your comments!
>> diff --git a/drivers/rtc/rtc-rp5c01.c b/drivers/rtc/rtc-rp5c01.c
>> index a95f733..36eb661 100644
>> --- a/drivers/rtc/rtc-rp5c01.c
>> +++ b/drivers/rtc/rtc-rp5c01.c
>> @@ -63,6 +63,8 @@ enum {
>> struct rp5c01_priv {
>> u32 __iomem *regs;
>> struct rtc_device *rtc;
>> + spinlock_t lock; /* against concurrent RTC/NVRAM access */
>> + struct bin_attribute nvram_attr;
>> };
>>
>> static inline unsigned int rp5c01_read(struct rp5c01_priv *priv,
>> @@ -92,6 +94,7 @@ static int rp5c01_read_time(struct device *dev, struct rtc_time *tm)
>> {
>> struct rp5c01_priv *priv = dev_get_drvdata(dev);
>>
>> + spin_lock_irq(&priv->lock);
>> rp5c01_lock(priv);
>>
>> tm->tm_sec = rp5c01_read(priv, RP5C01_10_SECOND) * 10 +
>> @@ -111,6 +114,7 @@ static int rp5c01_read_time(struct device *dev, struct rtc_time *tm)
>> tm->tm_year += 100;
>>
>> rp5c01_unlock(priv);
>> + spin_unlock_irq(&priv->lock);
>>
>> return rtc_valid_tm(tm);
>> }
>> @@ -119,6 +123,7 @@ static int rp5c01_set_time(struct device *dev, struct rtc_time *tm)
>> {
>> struct rp5c01_priv *priv = dev_get_drvdata(dev);
>>
>> + spin_lock_irq(&priv->lock);
>> rp5c01_lock(priv);
>>
>> rp5c01_write(priv, tm->tm_sec / 10, RP5C01_10_SECOND);
>> @@ -139,6 +144,7 @@ static int rp5c01_set_time(struct device *dev, struct rtc_time *tm)
>> rp5c01_write(priv, tm->tm_year % 10, RP5C01_1_YEAR);
>>
>> rp5c01_unlock(priv);
>> + spin_unlock_irq(&priv->lock);
>> return 0;
>> }
>>
>> @@ -147,6 +153,72 @@ static const struct rtc_class_ops rp5c01_rtc_ops = {
>> .set_time = rp5c01_set_time,
>> };
>>
>> +
>> +/*
>> + * The NVRAM is organized as 2 blocks of 13 nibbles of 4 bits.
>> + * We provide access to them like AmigaOS does: the high nibble of each 8-bit
>> + * byte is stored in BLOCK10, the low nibble in BLOCK11.
>> + */
>> +
>> +static ssize_t rp5c01_nvram_read(struct file *filp, struct kobject *kobj,
>> + struct bin_attribute *bin_attr,
>> + char *buf, loff_t pos, size_t size)
>> +{
>> + struct device *dev = container_of(kobj, struct device, kobj);
>> + struct rp5c01_priv *priv = dev_get_drvdata(dev);
>> + ssize_t count;
>> +
>> + spin_lock_irq(&priv->lock);
>> +
>> + for (count = 0; size > 0 && pos < RP5C01_MODE; count++, size--) {
>> + u8 data;
>> +
>> + rp5c01_write(priv,
>> + RP5C01_MODE_TIMER_EN | RP5C01_MODE_RAM_BLOCK10,
>> + RP5C01_MODE);
>> + data = rp5c01_read(priv, pos) << 4;
>> + rp5c01_write(priv,
>> + RP5C01_MODE_TIMER_EN | RP5C01_MODE_RAM_BLOCK11,
>> + RP5C01_MODE);
>> + data |= rp5c01_read(priv, pos++);
>> + rp5c01_write(priv, RP5C01_MODE_TIMER_EN | RP5C01_MODE_MODE01,
>> + RP5C01_MODE);
>> + *buf++ = data;
>> + }
>> +
>> + spin_unlock_irq(&priv->lock);
>> + return count;
>> +}
>> +
>> +static ssize_t rp5c01_nvram_write(struct file *filp, struct kobject *kobj,
>> + struct bin_attribute *bin_attr,
>> + char *buf, loff_t pos, size_t size)
>> +{
>> + struct device *dev = container_of(kobj, struct device, kobj);
>> + struct rp5c01_priv *priv = dev_get_drvdata(dev);
>> + ssize_t count;
>> +
>> + spin_lock_irq(&priv->lock);
>> +
>> + for (count = 0; size > 0 && pos < RP5C01_MODE; count++, size--) {
>> + u8 data = *buf++;
>> +
>> + rp5c01_write(priv,
>> + RP5C01_MODE_TIMER_EN | RP5C01_MODE_RAM_BLOCK10,
>> + RP5C01_MODE);
>> + rp5c01_write(priv, data >> 4, pos);
>> + rp5c01_write(priv,
>> + RP5C01_MODE_TIMER_EN | RP5C01_MODE_RAM_BLOCK11,
>> + RP5C01_MODE);
>> + rp5c01_write(priv, data & 0xf, pos++);
>> + rp5c01_write(priv, RP5C01_MODE_TIMER_EN | RP5C01_MODE_MODE01,
>> + RP5C01_MODE);
>> + }
>> +
>> + spin_unlock_irq(&priv->lock);
>> + return count;
>> +}
>> +
>> static int __init rp5c01_rtc_probe(struct platform_device *dev)
>> {
>> struct resource *res;
>> @@ -168,6 +240,15 @@ static int __init rp5c01_rtc_probe(struct platform_device *dev)
>> goto out_free_priv;
>> }
>>
>> + sysfs_bin_attr_init(&priv->nvram_attr);
>> + priv->nvram_attr.attr.name = "nvram";
>> + priv->nvram_attr.attr.mode = S_IRUGO | S_IWUSR;
>> + priv->nvram_attr.read = rp5c01_nvram_read;
>> + priv->nvram_attr.write = rp5c01_nvram_write;
>> + priv->nvram_attr.size = RP5C01_MODE;
>> +
>> + spin_lock_init(&priv->lock);
>> +
>> rtc = rtc_device_register("rtc-rp5c01", &dev->dev, &rp5c01_rtc_ops,
>> THIS_MODULE);
>> if (IS_ERR(rtc)) {
>> @@ -177,8 +258,15 @@ static int __init rp5c01_rtc_probe(struct platform_device *dev)
>>
>> priv->rtc = rtc;
>> platform_set_drvdata(dev, priv);
>> +
>> + error = sysfs_create_bin_file(&dev->dev.kobj, &priv->nvram_attr);
>> + if (error)
>> + goto out_unregister;
>> +
>> return 0;
>>
>> +out_unregister:
>> + rtc_device_unregister(rtc);
>> out_unmap:
>> iounmap(priv->regs);
>> out_free_priv:
>> @@ -190,6 +278,7 @@ static int __exit rp5c01_rtc_remove(struct platform_device *dev)
>> {
>> struct rp5c01_priv *priv = platform_get_drvdata(dev);
>>
>> + sysfs_remove_bin_file(&dev->dev.kobj, &priv->nvram_attr);
>> rtc_device_unregister(priv->rtc);
>> iounmap(priv->regs);
>> kfree(priv);
>> --
>> 1.7.0.4
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
--
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