linux-kernel - Re: [PATCH 2/3] hwmon: Add support for SPD5118 compliant temperature sensors

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Date: Thu, 30 May 2024 19:41:00 +0200
From: Armin Wolf <W_Armin@....de>
To: Guenter Roeck <linux@...ck-us.net>, linux-hwmon@...r.kernel.org
Cc: Hristo Venev <hristo@...ev.name>, René Rebe
 <rene@...ctcode.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Radu Sabau <radu.sabau@...log.com>
Subject: Re: [PATCH 2/3] hwmon: Add support for SPD5118 compliant temperature
 sensors

Am 30.05.24 um 19:33 schrieb Guenter Roeck:

> On 5/30/24 10:03, Armin Wolf wrote:
>> Am 29.05.24 um 22:52 schrieb Guenter Roeck:
>>
> [ ... ]
>
>>> +
>>> +temp1_lcrit_alarm    Temperature low critical alarm
>>> +temp1_min_alarm        Temperature low alarm
>>> +temp1_max_alarm        Temperature high alarm
>>> +temp1_crit_alarm    Temperature critical alarm
>>
>> Maybe it would be a good idea to tell users that the alarm attributes
>> are sticky.
>>
>
> The driver auto-clears them after read, so they are only sticky in the
> sense
> that they will remain active until read. This is quite common for
> hardware
> monitoring devices. However, sure, I'll add a note.
>
> [ ... ]
>
>>> +static int spd5118_write_enable(struct regmap *regmap, u32 attr,
>>> long val)
>>> +{
>>> +    if (val && val != 1)
>>> +        return -EINVAL;
>>> +
>>> +    return regmap_update_bits(regmap, SPD5118_REG_TEMP_CONFIG,
>>> +                  SPD5118_TS_DISABLE,
>>> +                  val ? 0 : SPD5118_TS_DISABLE);
>>
>> The spd5118 spec says that we have to wait 10ms after enabling the
>> sensors before
>> we start reading temperature values, maybe we need a delay + locking
>> here?
>>
>
> I don't think that would add much if any value but a lot of complexity
> for little gain. I find it acceptable that the sensor returns 0 for a
> few ms
> after enabling it. Pretty much all chips have the same problem, so I am
> really not concerned about it.
>
>>> +
>>> +static struct i2c_driver spd5118_driver = {
>>> +    .class        = I2C_CLASS_HWMON,
>>> +    .driver = {
>>> +        .name    = "spd5118",
>>> +        .of_match_table = spd5118_of_ids,
>>
>> The driver is missing suspend support, without it hibernation/S4
>> sleep will cause the
>> limit and config registers to be out of sync with the regmap cache.
>>
>
> Good point. Do you have a means to test this if I add suspend support ?
> I have not been able to figure out how to put my system into suspend.
>
> Thanks,
> Guenter
>
I think so, at least i can verify if S3 sleep works, but S4 sleep should work fine too.

Thanks,
Armin Wolf