[PATCH v6 0/9] TPM IRQ fixes

Lino Sanfilippo
2022-06-21T13:34:59Z

This series enables IRQ support for the TPM TIS core. For this reason a
number of bugfixes around the interrupt handling are required (patches 1 to
4).

Patch 5 takes into account that according to the TPM Interface
Specification stsValid and commandRead interrupts might not be supported
by the hardware. For this reason the supported interrupts are first queried
and stored. Then wait_for_tpm_stat() is adjusted to not wait for status
changes that are not reported by interrupts.

Patch 6 addresses the issue with concurrent locality handling:
Since the interrupt handler writes the interrupt status registers it needs
to hold the locality. However it runs concurrently to the thread which
triggered the interrupt (e.g. by reading or writing data to the TPM). So
it must take care when claiming and releasing the locality itself,
because it may race with the concurrent running thread which also claims
and releases the locality.
To avoid that both interrupt and concurrent running thread interfere with
each other a locality counter is used which guarantees that at any time
the locality is held as long as it is required by one of both execution
paths.

Patch 7 implements the request of a threaded interrupt handler. This is
needed since SPI uses a mutex for data transmission and since we access the
interrupt status register via SPI in the irq handler we need a sleepable
context.

Patch 8 makes sure that writes to the interrupt register are effective if
done in the interrupt handler.

Patch 9 enables the test for interrupts by setting the required flag before
the test is executed.

Changes in v6:
- set TPM_TIS_IRQ_TESTED in flag member of the tpm_tis_data struct instead
in an own bitfield
- improve commit messages
- use int_mask instead of irqs_in_use as variable name
- use sts_mask instead of active_irqs as variable name
- squash patch 5 and 6
- prefix functions with tpm_tis_
- remove "fixes" tag

Changes in v5:
- improve commit message of patch 1 as requested by Jarko
- drop patch that makes locality handling simpler by only claiming it at
driver startup and releasing it at driver shutdown (requested by Jarko)
- drop patch that moves the interrupt test from tpm_tis_send()
to tmp_tis_probe_irq_single() as requested by Jarko
- add patch to make locality handling threadsafe so that it can also be
done by the irq handler
- separate logical changes into own patches
- always request threaded interrupt handler

Changes in v4:
- only request threaded irq in case of SPI as requested by Jarko.
- reimplement patch 2 to limit locality handling changes to the TIS core.
- separate fixes from cleanups as requested by Jarko.
- rephrase commit messages

Changes in v3:
- fixed compiler error reported by kernel test robot
- rephrased commit message as suggested by Jarko Sakkinen
- added Reviewed-by tag

Changes in v2:
- rebase against 5.12
- free irq on error path

Lino Sanfilippo (9):
tpm, tpm_tis: Avoid cache incoherency in test for interrupts
tpm, tpm_tis: Claim locality before writing TPM_INT_ENABLE register
tpm, tpm_tis: Disable interrupts if tpm_tis_probe_irq() failed
tpm, tmp_tis: Claim locality before writing interrupt registers
tpm, tpm_tis: Only handle supported interrupts
tmp, tmp_tis: Implement usage counter for locality
tpm, tpm_tis: Request threaded interrupt handler
tpm, tpm_tis: Claim locality in interrupt handler
tpm, tpm_tis: Enable interrupt test

drivers/char/tpm/tpm_tis.c | 2 +-
drivers/char/tpm/tpm_tis_core.c | 252 +++++++++++++++++++++-----------
drivers/char/tpm/tpm_tis_core.h | 5 +-
3 files changed, 171 insertions(+), 88 deletions(-)

base-commit: 78ca55889a549a9a194c6ec666836329b774ab6d
--
2.36.1