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

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Date: Thu, 30 May 2024 06:27:27 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Thomas Weißschuh <thomas@...ch.de>
Cc: linux-hwmon@...r.kernel.org, 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

On 5/30/24 02:08, Thomas Weißschuh wrote:
> On 2024-05-29 13:52:03+0000, Guenter Roeck wrote:
>> Add support for SPD5118 (Jedec JESD300-5B.01) compliant temperature
>> sensors. Such sensors are typically found on DDR5 memory modules.
>>
>> Cc: René Rebe <rene@...ctcode.de>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
> 
> <snip>
> 
>> +/* Return 0 if detection is successful, -ENODEV otherwise */
>> +static int spd5118_detect(struct i2c_client *client, struct i2c_board_info *info)
>> +{
>> +	struct i2c_adapter *adapter = client->adapter;
>> +	int regval;
>> +
>> +	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
>> +				     I2C_FUNC_SMBUS_WORD_DATA))
>> +		return -ENODEV;
>> +
>> +	regval = i2c_smbus_read_word_swapped(client, SPD5118_REG_TYPE);
>> +	if (regval != 0x5118)
>> +		return -ENODEV;
>> +
>> +	regval = i2c_smbus_read_word_data(client, SPD5118_REG_VENDOR);
>> +	if (regval < 0 || !spd5118_vendor_valid(regval & 0xff, regval >> 8))
>> +		return -ENODEV;
>> +
>> +	regval = i2c_smbus_read_byte_data(client, SPD5118_REG_CAPABILITY);
>> +	if (regval < 0)
>> +		return -ENODEV;
>> +
>> +	regval = i2c_smbus_read_byte_data(client, SPD5118_REG_TEMP_CLR);
>> +	if (regval)
>> +		return -ENODEV;
>> +	regval = i2c_smbus_read_byte_data(client, SPD5118_REG_ERROR_CLR);
>> +	if (regval)
>> +		return -ENODEV;
>> +
>> +	if (!(regval & SPD5118_CAP_TS_SUPPORT) || (regval & 0xfc))
>> +		return -ENODEV;
> 
> This breaks automatic detection for me.
> 
> I think the test should after the read of SPD5118_REG_CAPABILITY and
> test that register, similar on how it is done in _probe().
> 

Yes, that got messed up when I added reading SPD5118_REG_TEMP_CLR and
SPD5118_REG_ERROR_CLR in the last minute. Thanks!

Thanks,
Guenter