tree fff1c50e77544b0c9ee9e9573867eb2a3e05bd47
parent 1fbc5e95356a4600fab3a04a82dc8bb49591aedd
author Jason Gunthorpe <jgunthorpe@obsidianresearch.com> 1353532554 -0800
committer Kent Yoder <key@linux.vnet.ibm.com> 1360078704 -0600

TPM: Work around buggy TPMs that block during continue self test

We've been testing an alternative TPM for our embedded products and
found random kernel boot failures due to time outs after the continue
self test command.

This was happening randomly, and has been *very* hard to track down, but
it
looks like with this chip there is some kind of race with the
tpm_tis_status()
check of TPM_STS_COMMAND_READY. If things get there 'too fast' then
it sees the chip is ready, or tpm_tis_ready() works. Otherwise it takes
somewhere over 400ms before the chip will return TPM_STS_COMMAND_READY.

Adding some delay after tpm_continue_selftest() makes things reliably
hit the failure path, otherwise it is a crapshot.

The spec says it should be returning TPM_WARN_DOING_SELFTEST, not
holding
off on ready..

Boot log during this event looks like this:

tpm_tis 70030000.tpm_tis: 1.2 TPM (device-id 0x3204, rev-id 64)
tpm_tis 70030000.tpm_tis: Issuing TPM_STARTUP
tpm_tis 70030000.tpm_tis: tpm_transmit: tpm_send: error -62
tpm_tis 70030000.tpm_tis: [Hardware Error]: TPM command timed out during
continue self test
tpm_tis 70030000.tpm_tis: tpm_transmit: tpm_send: error -62
tpm_tis 70030000.tpm_tis: [Hardware Error]: TPM command timed out during
continue self test
tpm_tis 70030000.tpm_tis: tpm_transmit: tpm_send: error -62
tpm_tis 70030000.tpm_tis: [Hardware Error]: TPM command timed out during
continue self test
tpm_tis 70030000.tpm_tis: tpm_transmit: tpm_send: error -62
tpm_tis 70030000.tpm_tis: [Hardware Error]: TPM command timed out during
continue self test

The other TPM vendor we use doesn't show this wonky behaviour:
tpm_tis 70030000.tpm_tis: 1.2 TPM (device-id 0xFE, rev-id 70)

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com>