> On Jul 9, 2021, at 10:47 AM, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote:
>
> On Thu, Jul 08, 2021 at 09:40:28PM -0700, Hao Wu wrote:
>> The Atmel TPM 1.2 chips crash with error
>> `tpm_try_transmit: send(): error -62` since kernel 4.14.
>> It is observed from the kernel log after running `tpm_sealdata -z`.
>> The error thrown from the command is as follows
>> ```
>> $ tpm_sealdata -z
>> Tspi_Key_LoadKey failed: 0x00001087 - layer=tddl,
>> code=0087 (135), I/O error
>> ```
>>
>> The issue was reproduced with the following Atmel TPM chip:
>> ```
>> $ tpm_version
>> T0 TPM 1.2 Version Info:
>> Chip Version: 1.2.66.1
>> Spec Level: 2
>> Errata Revision: 3
>> TPM Vendor ID: ATML
>> TPM Version: 01010000
>> Manufacturer Info: 41544d4c
>> ```
>>
>> The root cause of the issue is due to the TPM calls to msleep()
>> were replaced with usleep_range() [1], which reduces
>> the actual timeout. Via experiments, it is observed that
>> the original msleep(5) actually sleeps for 15ms.
>> Because of a known timeout issue in Atmel TPM 1.2 chip,
>> the shorter timeout than 15ms can cause the error described above.
>>
>> A few further changes in kernel 4.16 [2] and 4.18 [3, 4] further
>> reduced the timeout to less than 1ms. With experiments,
>> the problematic timeout in the latest kernel is the one
>> for `wait_for_tpm_stat`.
>>
>> To fix it, the patch reverts the timeout of `wait_for_tpm_stat`
>> to 15ms for all Atmel TPM 1.2 chips, but leave it untouched
>> for Ateml TPM 2.0 chip, and chips from other vendors.
>> As explained above, the chosen 15ms timeout is
>> the actual timeout before this issue introduced,
>> thus the old value is used here.
>> Particularly, TPM_ATML_TIMEOUT_WAIT_STAT_MIN is set to 14700us,
>> TPM_ATML_TIMEOUT_WAIT_STAT_MIN is set to 15000us according to
>> the existing TPM_TIMEOUT_RANGE_US (300us).
>> The fixed has been tested in the system with the affected Atmel chip
>> with no issues observed after boot up.
>>
>> References:
>> [1] 9f3fc7bcddcb tpm: replace msleep() with usleep_range() in TPM
>> 1.2/2.0 generic drivers
>> [2] cf151a9a44d5 tpm: reduce tpm polling delay in tpm_tis_core
>> [3] 59f5a6b07f64 tpm: reduce poll sleep time in tpm_transmit()
>> [4] 424eaf910c32 tpm: reduce polling time to usecs for even finer
>> granularity
>>
>> Fixes: 9f3fc7bcddcb ("tpm: replace msleep() with usleep_range() in TPM 1.2/2.0 generic drivers")
>> Link: https://patchwork.kernel.org/project/linux-integrity/patch/20200926223150.109645-1-hao.wu@xxxxxxxxxx/
>> Signed-off-by: Hao Wu <hao.wu@xxxxxxxxxx>
>> ---
>> This version (v2) has following changes on top of the last (v1):
>> - follow the existing way to define two timeouts (min and max)
>> for ATMEL chip, thus keep the exact timeout logic for
>> non-ATEML chips.
>> - limit the timeout increase to only ATMEL TPM 1.2 chips,
>> because it is not an issue for TPM 2.0 chips yet.
>>
>> Test Plan:
>> - Run fixed kernel with ATMEL TPM chips and see crash has been fixed.
>> - Run fixed kernel with non-ATMEL TPM chips, and confirm
>> the timeout has not been changed.
>>
>> drivers/char/tpm/tpm.h | 6 ++++--
>> drivers/char/tpm/tpm_tis_core.c | 23 +++++++++++++++++++++--
>> include/linux/tpm.h | 3 +++
>> 3 files changed, 28 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>> index 283f78211c3a..6de1b44c4aab 100644
>> --- a/drivers/char/tpm/tpm.h
>> +++ b/drivers/char/tpm/tpm.h
>> @@ -41,8 +41,10 @@ enum tpm_timeout {
>> TPM_TIMEOUT_RETRY = 100, /* msecs */
>> TPM_TIMEOUT_RANGE_US = 300, /* usecs */
>> TPM_TIMEOUT_POLL = 1, /* msecs */
>> - TPM_TIMEOUT_USECS_MIN = 100, /* usecs */
>> - TPM_TIMEOUT_USECS_MAX = 500 /* usecs */
>> + TPM_TIMEOUT_USECS_MIN = 100, /* usecs */
>> + TPM_TIMEOUT_USECS_MAX = 500, /* usecs */
>> + TPM_ATML_TIMEOUT_WAIT_STAT_MIN = 14700, /* usecs */
>> + TPM_ATML_TIMEOUT_WAIT_STAT_MAX = 15000 /* usecs */
>> };
>>
>> /* TPM addresses */
>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
>> index 55b9d3965ae1..ae27d66fdd94 100644
>> --- a/drivers/char/tpm/tpm_tis_core.c
>> +++ b/drivers/char/tpm/tpm_tis_core.c
>> @@ -80,8 +80,17 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
>> }
>> } else {
>> do {
>> - usleep_range(TPM_TIMEOUT_USECS_MIN,
>> - TPM_TIMEOUT_USECS_MAX);
>> + /* this code path could be executed before
>> + * timeouts initialized in chip instance.
>> + */
>> + if (chip->timeout_wait_stat_min &&
>> + chip->timeout_wait_stat_max)
>> + usleep_range(chip->timeout_wait_stat_min,
>> + chip->timeout_wait_stat_max);
>> + else
>> + usleep_range(TPM_TIMEOUT_USECS_MIN,
>> + TPM_TIMEOUT_USECS_MAX);
>
> This starts to look otherwise fine but you don't need this condition.
> Just initialize variables to TPM_TIMEOUT_USECS_{MIN, MAX} for non-Atmel.
Not sure I got your point or not. We have discussed this question a few rounds before,
I answered you about this. This check is required because before the time of
Initialization in the code I added in `tpm_tis_core_init`
```
+ chip->timeout_wait_stat_min = TPM_TIMEOUT_USECS_MIN;
+ chip->timeout_wait_stat_max = TPM_TIMEOUT_USECS_MAX;
```
The func `wait_for_tpm_stat` runs, we need the condition to fall back to avoid system startup crash.
Let me know if this makes sense. If needed, I can do another confirm.
> /Jarkko
Hao
