linux-kernel - Re: [PATCH 2/2] rtc: bq32k: Fix handling of oscillator failure flag

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Date:	Thu, 11 Aug 2016 12:15:20 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Daniel Romell <danielromell@...il.com>
Cc:	a.zummo@...ertech.it, rtc-linux@...glegroups.com,
	linux-kernel@...r.kernel.org, daro@....se, jao@....se, mago@....se
Subject: Re: [PATCH 2/2] rtc: bq32k: Fix handling of oscillator failure flag

On 11/08/2016 at 11:59:15 +0200, Daniel Romell wrote :
> From: Jan Östlund <jao@....se>
> 
> While the oscillator failure flag is set, the RTC registers
> should be considered invalid. bq32k_rtc_read_time() now
> returns an error instead of an invalid time.
> 
> The failure flag is cleared the next time the clock is set.
> 
> Signed-off-by: Daniel Romell <daro@....se>
> ---
>  drivers/rtc/rtc-bq32k.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-bq32k.c b/drivers/rtc/rtc-bq32k.c
> index 5a0c137..3fc6f7c 100644
> --- a/drivers/rtc/rtc-bq32k.c
> +++ b/drivers/rtc/rtc-bq32k.c
> @@ -93,6 +93,13 @@ static int bq32k_rtc_read_time(struct device *dev, struct rtc_time *tm)
>  	if (error)
>  		return error;
>  
> +	/*
> +	 * In case of oscillator failure, the register contents should be
> +	 * considered invalid. The flag is cleared the next time the RTC is set.
> +	 */
> +	if (regs.minutes & BQ32K_OF)
> +		return -EIO;

The other drivers return -EINVAL in that case. Else, the change is fine.

> +
>  	tm->tm_sec = bcd2bin(regs.seconds & BQ32K_SECONDS_MASK);
>  	tm->tm_min = bcd2bin(regs.minutes & BQ32K_MINUTES_MASK);
>  	tm->tm_hour = bcd2bin(regs.cent_hours & BQ32K_HOURS_MASK);
> @@ -204,13 +211,10 @@ static int bq32k_probe(struct i2c_client *client,
>  
>  	/* Check Oscillator Failure flag */
>  	error = bq32k_read(dev, &reg, BQ32K_MINUTES, 1);
> -	if (!error && (reg & BQ32K_OF)) {
> -		dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
> -		reg &= ~BQ32K_OF;
> -		error = bq32k_write(dev, &reg, BQ32K_MINUTES, 1);
> -	}
>  	if (error)
>  		return error;
> +	if (reg & BQ32K_OF)
> +		dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
>  
>  	if (client->dev.of_node)
>  		trickle_charger_of_init(dev, client->dev.of_node);
> -- 
> 2.7.4
> 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com