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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c7c90be3-8dcd-4737-9fce-01343da01855@seco.com>
Date: Thu, 25 Jan 2024 12:14:55 -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 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