diff options
| author | Kyösti Mälkki <kyosti.malkki@gmail.com> | 2023-07-06 06:20:31 +0300 |
|---|---|---|
| committer | Martin L Roth <gaumless@gmail.com> | 2024-10-14 15:25:57 +0000 |
| commit | 71c8dac9ca9915b7f954c33e128b022f0381dd10 (patch) | |
| tree | 492d917f14ceb1ec34bd0a30f497038eb09d10a1 /src/drivers/pc80/tpm/tis.c | |
| parent | 910f706bbd9aa50fbd168de4ba197547ab00a0dc (diff) | |
drivers/pc80/tpm: Fix tis_readresponse()
TPM_RDRESP_NEED_DELAY was introduced in 2018 in CB:25322 after
observing errors with SLB9635 by Infineon. It has been confirmed
also SLB9670 and SLB9672 require a fix or delay here.
Presumably, prior to CB:4388 SLB9635 did not have this problem,
as this particular TPM shipped with samsung/lumpy Chromebook since
2011. In CB:4388 the code changed from polling the status register
(+burst_count) using a 32bit read to separated 8bit reads.
So far, experiments on samsung/lumpy and SLB9635 indicate that
it would be sufficient to add a single tpm_read_status() call
to see TIS_STS_DATA_AVAILABLE as set at the time of evaluating
the loop exit condition.
Change-Id: If5c3e93c7946ebf8226f7bba47b38253f6920c61
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Co-authored-by: Bill XIE <persmule@hardenedlinux.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76315
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Bill XIE <persmule@hardenedlinux.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Diffstat (limited to 'src/drivers/pc80/tpm/tis.c')
| -rw-r--r-- | src/drivers/pc80/tpm/tis.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/src/drivers/pc80/tpm/tis.c b/src/drivers/pc80/tpm/tis.c index 3f863a36da..93cb2a6163 100644 --- a/src/drivers/pc80/tpm/tis.c +++ b/src/drivers/pc80/tpm/tis.c @@ -286,6 +286,14 @@ static inline tpm_result_t tis_wait_valid_data(int locality) static inline int tis_has_valid_data(int locality) { const u8 has_data = TIS_STS_DATA_AVAILABLE | TIS_STS_VALID; + + /* + * Certain TPMs require a small delay here, as they have set + * TIS_STS_VALID first and TIS_STS_DATA_AVAILABLE few clocks later. + */ + if ((tpm_read_status(locality) & has_data) == has_data) + return 1; + return (tpm_read_status(locality) & has_data) == has_data; } @@ -635,14 +643,6 @@ static tpm_result_t tis_readresponse(u8 *buffer, size_t *len) if (offset == expected_count) break; /* We got all we need */ - /* - * Certain TPMs seem to need some delay between tis_wait_valid() - * and tis_has_valid_data(), or some race-condition-related - * issue will occur. - */ - if (CONFIG(TPM_RDRESP_NEED_DELAY)) - udelay(10); - } while (tis_has_valid_data(locality)); /* * Make sure we indeed read all there was. */ |