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Re: [PATCH] Added MIPS RM9K watchdog driver

To: Dave Jones <davej@redhat.com>
Subject: Re: [PATCH] Added MIPS RM9K watchdog driver
From: Thomas Koeller <thomas@koeller.dyndns.org>
Date: Sat, 12 Aug 2006 01:49:23 +0200
Cc: wim@iguana.be, linux-kernel@vger.kernel.org, Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org
In-reply-to: <20060811205639.GK26930@redhat.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200608102319.13679.thomas@koeller.dyndns.org> <20060811205639.GK26930@redhat.com>
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On Friday 11 August 2006 22:56, Dave Jones wrote:
> On Thu, Aug 10, 2006 at 11:19:13PM +0200, thomas@koeller.dyndns.org wrote:
>  > This is a driver for the on-chip watchdog device found on some
>  > MIPS RM9000 processors.
>  >
>  > Signed-off-by: Thomas Koeller <thomas.koeller@baslerweb.com>
>
> Mostly same nit-picking comments as your other driver..

Which one?

>
>  > +++ b/drivers/char/watchdog/rm9k_wdt.c
>  > ...
>  > +
>  > +#include <linux/config.h>
>
> not needed.

It is, otherwise I do not get CONFIG_WATCHDOG_NOWAYOUT.

>
>  > +/* Function prototypes */
>  > +static int __init wdt_gpi_probe(struct device *);
>  > +static int __exit wdt_gpi_remove(struct device *);
>  > +static void wdt_gpi_set_timeout(unsigned int);
>  > +static int wdt_gpi_open(struct inode *, struct file *);
>  > +static int wdt_gpi_release(struct inode *, struct file *);
>  > +static ssize_t wdt_gpi_write(struct file *, const char __user *,
>  > size_t, loff_t *);
>  > +static long wdt_gpi_ioctl(struct file *, unsigned int, unsigned long);
>  > +static const struct resource *wdt_gpi_get_resource(struct
>  > platform_device *, const char *, unsigned int);
>  > +static int wdt_gpi_notify(struct notifier_block *, unsigned long, void
>  > *); +static irqreturn_t wdt_gpi_irqhdl(int, void *, struct pt_regs *);
>
> Can probably (mostly?) go away with some creative reordering.

Probably, but should it? I always considered it good style to have
prototypes for all functions.

>
>  > +static int locked = 0;
>
> unneeded initialisation.

Not strictly needed, that's true, but does not do any harm either
and expresses the intention clearly.

>
>  > +static int nowayout =
>  > +#if defined(CONFIG_WATCHDOG_NOWAYOUT)
>  > +  1;
>  > +#else
>  > +  0;
>  > +#endif
>
> static int nowayout = CONFIG_WATCHDOG_NOWAYOUT;
>
> should work.

Does not work. If the option is not selected, CONFIG_WATCHDOG_NOWAYOUT
is undefined, not zero.

>
>  > +static void wdt_gpi_set_timeout(unsigned int to)
>  > +{
>  > +  u32 reg;
>  > +  const u32 wdval = (to * CLOCK) & ~0x0000000f;
>  > +
>  > +  lock_titan_regs();
>  > +  reg = titan_readl(CPCCR) & ~(0xf << (wd_ctr * 4));
>  > +  titan_writel(reg, CPCCR);
>  > +  wmb();
>  > +  __raw_writel(wdval, wd_regs + 0x0000);
>  > +  wmb();
>  > +  titan_writel(reg | (0x2 << (wd_ctr * 4)), CPCCR);
>  > +  wmb();
>  > +  titan_writel(reg | (0x5 << (wd_ctr * 4)), CPCCR);
>  > +  iob();
>  > +  unlock_titan_regs();
>  > +}
>
> As in the previous driver, are these barriers strong enough?
> Or do they need explicit reads of the written addresses to flush the write?

I think they are. Remember, the entire device is integrated in the
processor. No external buses involved.

>
>               Dave

Thanks for your comments!

Thomas

-- 
Thomas Koeller
thomas@koeller.dyndns.org

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