linux-kernel - Re: [PATCH v3] rtc: abx80x: Don't warn about oscillator failure after PoR

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Date: Fri, 21 Jun 2024 11:23:58 -0400
From: Sean Anderson <sean.anderson@...o.com>
To: Alessandro Zummo <a.zummo@...ertech.it>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>, linux-rtc@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
 Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH v3] rtc: abx80x: Don't warn about oscillator failure after
 PoR

On 1/25/24 12:14, Sean Anderson wrote:
> On 1/8/24 17:05, Sean Anderson wrote:
>> On 12/11/23 11:03, Sean Anderson wrote:
>>> On 10/19/23 12:39, Sean Anderson wrote:
>>>> According to the datasheet, the "oscillator failure" bit is set
>>>> 
>>>>> ...on a power on reset, when both the system and battery voltages have
>>>>> dropped below acceptable levels. It is also set if an Oscillator Failure
>>>>> occurs....
>>>> 
>>>> From testing, this bit is also set if a software reset is initiated.
>>>> 
>>>> This bit has a confusing name; it really tells us whether the time data
>>>> is valid. We clear it when writing the time. If it is still set, that
>>>> means there is a persistent issue (such as an oscillator failure),
>>>> instead of a transient one (such as power loss).
>>>> 
>>>> Because there are several other reasons which might cause this bit
>>>> to be set (including booting for the first time or a battery failure),
>>>> do not warn about oscillator failures willy-nilly. This may cause system
>>>> integrators to waste time looking into the wrong line of investigation.
>>>> 
>>>> We continue printing a message about invalid time data or an oscillator
>>>> failure. There is no voltimeter in this RTC, so this is the best
>>>> indication that the battery is dead (or dying) and reeds replacement.
>>>> 
>>>> Signed-off-by: Sean Anderson <sean.anderson@...o.com>
>>>> ---
>>>> Note that the following drivers all warn when they detect a problem with
>>>> the oscillator:
>>>> 
>>>> drivers/rtc/rtc-ds1672.c
>>>> drivers/rtc/rtc-pcf*.c
>>>> drivers/rtc/rtc-rs5c*.c
>>>> drivers/rtc/rtc-sc27xx.c
>>>> 
>>>> So warning about such an error has good precedent.
>>>> 
>>>> Changes in v3:
>>>> - Use info since this is a good indication of a battery failure
>>>> 
>>>> Changes in v2:
>>>> - Use debug instead of info in the typical case (no battery)
>>>> 
>>>>  drivers/rtc/rtc-abx80x.c | 17 ++++++++++++++++-
>>>>  1 file changed, 16 insertions(+), 1 deletion(-)
>>>> 
>>>> diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
>>>> index fde2b8054c2e..f463a58a240b 100644
>>>> --- a/drivers/rtc/rtc-abx80x.c
>>>> +++ b/drivers/rtc/rtc-abx80x.c
>>>> @@ -127,6 +127,7 @@ struct abx80x_priv {
>>>>  	struct rtc_device *rtc;
>>>>  	struct i2c_client *client;
>>>>  	struct watchdog_device wdog;
>>>> +	bool wrote_time;
>>>>  };
>>>>  
>>>>  static int abx80x_write_config_key(struct i2c_client *client, u8 key)
>>>> @@ -179,6 +180,7 @@ static int abx80x_enable_trickle_charger(struct i2c_client *client,
>>>>  static int abx80x_rtc_read_time(struct device *dev, struct rtc_time *tm)
>>>>  {
>>>>  	struct i2c_client *client = to_i2c_client(dev);
>>>> +	struct abx80x_priv *priv = i2c_get_clientdata(client);
>>>>  	unsigned char buf[8];
>>>>  	int err, flags, rc_mode = 0;
>>>>  
>>>> @@ -193,7 +195,18 @@ static int abx80x_rtc_read_time(struct device *dev, struct rtc_time *tm)
>>>>  			return flags;
>>>>  
>>>>  		if (flags & ABX8XX_OSS_OF) {
>>>> -			dev_err(dev, "Oscillator failure, data is invalid.\n");
>>>> +			/*
>>>> +			 * The OF bit can be set either because of a reset
>>>> +			 * (PoR/Software reset) or because of an oscillator
>>>> +			 * failure. Effectively, it indicates that the stored
>>>> +			 * time is invalid. When we write the time, we clear
>>>> +			 * this bit. If it stays set, then this indicates an
>>>> +			 * oscillator failure.
>>>> +			 */
>>>> +			if (priv->wrote_time)
>>>> +				dev_err(dev, "Oscillator failure\n");
>>>> +			else
>>>> +				dev_info(dev, "Time data invalid\n");
>>>>  			return -EINVAL;
>>>>  		}
>>>>  	}
>>>> @@ -219,6 +232,7 @@ static int abx80x_rtc_read_time(struct device *dev, struct rtc_time *tm)
>>>>  static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
>>>>  {
>>>>  	struct i2c_client *client = to_i2c_client(dev);
>>>> +	struct abx80x_priv *priv = i2c_get_clientdata(client);
>>>>  	unsigned char buf[8];
>>>>  	int err, flags;
>>>>  
>>>> @@ -252,6 +266,7 @@ static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
>>>>  		dev_err(&client->dev, "Unable to write oscillator status register\n");
>>>>  		return err;
>>>>  	}
>>>> +	priv->wrote_time = true;
>>>>  
>>>>  	return 0;
>>>>  }
>>> 
>>> ping?
>> 
>> ping again?
> 
> Does anyone read this list? This patch has gone unreviewed since December of 2022!
> 
> --Sean

ping again