linux-kernel - Re: [PATCH RFC 2/2] tpm: tpm_tis: Provide error messages in tpm_tis_core

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Message-ID: <357a8f1d-033c-4d55-a6d3-05703cc7e0b0@gmx.net>
Date: Fri, 6 Sep 2024 16:42:31 +0200
From: Stefan Wahren <wahrenst@....net>
To: Jarkko Sakkinen <jarkko@...nel.org>, Peter Huewe <peterhuewe@....de>,
 Jason Gunthorpe <jgg@...pe.ca>
Cc: linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
 Stefan Berger <stefanb@...ux.ibm.com>
Subject: Re: [PATCH RFC 2/2] tpm: tpm_tis: Provide error messages in
 tpm_tis_core_init

Am 06.09.24 um 11:50 schrieb Jarkko Sakkinen:
> On Fri Sep 6, 2024 at 9:09 AM EEST, Stefan Wahren wrote:
>> In case of SPI wiring issues (e.g. MISO pin permanent high) the
>> core init won't provide any error message on failure. Add some
>> helpful error messages to tpm_tis_core_init(), which helps
>> to better understand why the driver won't probe.
>>
>> Signed-off-by: Stefan Wahren <wahrenst@....net>
>> ---
>>   drivers/char/tpm/tpm_tis_core.c | 15 ++++++++++++---
>>   1 file changed, 12 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
>> index fdef214b9f6b..830e331fcebe 100644
>> --- a/drivers/char/tpm/tpm_tis_core.c
>> +++ b/drivers/char/tpm/tpm_tis_core.c
>> @@ -1133,8 +1133,10 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>>   	dev_set_drvdata(&chip->dev, priv);
>>
>>   	rc = tpm_tis_read32(priv, TPM_DID_VID(0), &vendor);
>> -	if (rc < 0)
>> +	if (rc < 0) {
>> +		dev_err(dev, "Failed to read TPM_DID_VID register: %d\n", rc);
>>   		return rc;
>> +	}
>>
>>   	priv->manufacturer_id = vendor;
>>
>> @@ -1162,19 +1164,25 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>>   		chip->ops->clk_enable(chip, true);
>>
>>   	if (wait_startup(chip, 0) != 0) {
>> +		dev_err(dev, "TPM device not accessible (0x%0x)\n",
>> +			vendor);
>>   		rc = -ENODEV;
>>   		goto out_err;
>>   	}
>>
>>   	/* Take control of the TPM's interrupt hardware and shut it off */
>>   	rc = tpm_tis_read32(priv, TPM_INT_ENABLE(priv->locality), &intmask);
>> -	if (rc < 0)
>> +	if (rc < 0) {
>> +		dev_err(dev, "Failed to read TPM_INT_ENABLE register: %d\n", rc);
>>   		goto out_err;
>> +	}
>>
>>   	/* Figure out the capabilities */
>>   	rc = tpm_tis_read32(priv, TPM_INTF_CAPS(priv->locality), &intfcaps);
>> -	if (rc < 0)
>> +	if (rc < 0) {
>> +		dev_err(dev, "Failed to read TPM_INTF_CAPS register: %d\n", rc);
>>   		goto out_err;
>> +	}
>>
>>   	dev_dbg(dev, "TPM interface capabilities (0x%x):\n",
>>   		intfcaps);
>> @@ -1209,6 +1217,7 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>>
>>   	rc = tpm_tis_request_locality(chip, 0);
>>   	if (rc < 0) {
>> +		dev_err(dev, "Failed to request locality (0x%0x)\n", vendor);
>>   		rc = -ENODEV;
>>   		goto out_err;
>>   	}
>> --
>> 2.34.1
> No thanks. It not only adds helpful messages but has potential to add
> unwanted merge conflicts.
So this is a general NAK?

So with every setup where the driver exits without an error message, the
developer should add its own debug?
>
> BR, Jarkko