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

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Message-ID: <ff40a221-38b5-40d7-a0fc-cf617853a096@seco.com>
Date: Mon, 8 Jan 2024 17:05:47 -0500
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
Subject: Re: [PATCH v3] rtc: abx80x: Don't warn about oscillator failure after
 PoR

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?