Messages in this thread | | | Date | Sun, 13 Jun 2010 19:44:56 +0200 | Subject | Re: [rtc-linux] [PATCH] rtc: rp5c01 - Add NVRAM support | From | Geert Uytterhoeven <> |
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On Sun, Jun 13, 2010 at 15:41, Wan ZongShun <mcuos.com@gmail.com> wrote: > Minior comment below: > > 2010/6/13 Geert Uytterhoeven <geert@linux-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@linux-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@linux-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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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