[PATCH] NUC900/rtc: change the waiting for device ready implement

[akpm@linux-foundation.org (Andrew Morton)]

On Thu, 27 May 2010 14:59:31 +0800
Wan ZongShun <mcuos.com@gmail.com> wrote:

> Dear Andrew,
> 
> This patch is only to change the waiting for device ready implement
> for winbond nuc900 platform.
> 

It's not very helpful to only say "I changed it".  _why_ did you change
it?  What change did you make?  What was wrong with the old code and
what's better about the new code?

> --- a/drivers/rtc/rtc-nuc900.c
> +++ b/drivers/rtc/rtc-nuc900.c
> @@ -85,22 +85,21 @@ static irqreturn_t nuc900_rtc_interrupt(int irq, void *_rtc)
> 
>  static int *check_rtc_access_enable(struct nuc900_rtc *nuc900_rtc)
>  {
> -	unsigned int i;
> +	unsigned int i, timeout = 0x1000;
>  	__raw_writel(INIRRESET, nuc900_rtc->rtc_reg + REG_RTC_INIR);
> 
>  	mdelay(10);
> 
>  	__raw_writel(AERPOWERON, nuc900_rtc->rtc_reg + REG_RTC_AER);
> 
> -	for (i = 0; i < 1000; i++) {
> -		if (__raw_readl(nuc900_rtc->rtc_reg + REG_RTC_AER) & AERRWENB)
> -			return 0;
> -	}
> +	while (!(__raw_readl(nuc900_rtc->rtc_reg + REG_RTC_AER) & AERRWENB)
> +								&& timeout--)
> +		mdelay(1);
> 
> -	if ((__raw_readl(nuc900_rtc->rtc_reg + REG_RTC_AER) & AERRWENB) == 0x0)
> -		return ERR_PTR(-ENODEV);
> +	if (!timeout)
> +		return ERR_PTR(-EPERM);
> 
> -	return ERR_PTR(-EPERM);
> +	return 0;
> }

I can see that the patch makes two changes: it adds an mdelay(1) to the
polling loop and it changes the return value from ENODEV to EPERM if
the loop timed out.

But I don't have the faintest idea _why_ the changes were made!


So.  I merged the patch without a changelog.  Please send a changelog
for this patch which permits others to understand the change.