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    SubjectRe: [rtc-linux] [PATCH] rtc: rp5c01 - Add NVRAM support
    From
    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
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