On a Chromebook I'm working on I noticed a big (~1 second) delay
during bootup where nothing was happening. Right around this big
delay there were messages about the TPM:
[ 2.311352] tpm_tis_spi spi0.0: TPM ready IRQ confirmed on attempt 2
[ 3.332790] tpm_tis_spi spi0.0: Cr50 firmware version: ...
I put a few printouts in and saw that tpm_tis_spi_init() (specifically
tpm_chip_register() in that function) was taking the lion's share of
this time, though ~115 ms of the time was in cr50_print_fw_version().
Let's make a one-line change to prefer async probe for tpm_tis_spi.
There's no reason we need to block other drivers from probing while we
load.
NOTES:
* It's possible that other hardware runs through the init sequence
faster than Cr50 and this isn't such a big problem for them.
However, even if they are faster they are still doing _some_
transfers over a SPI bus so this should benefit everyone even if to
a lesser extent.
* It's possible that there are extra delays in the code that could be
optimized out. I didn't dig since once I enabled async probe they
no longer impacted me.
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
drivers/char/tpm/tpm_tis_spi_main.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/char/tpm/tpm_tis_spi_main.c b/drivers/char/tpm/tpm_tis_spi_main.c
index d96755935529..422766445373 100644
--- a/drivers/char/tpm/tpm_tis_spi_main.c
+++ b/drivers/char/tpm/tpm_tis_spi_main.c
@@ -288,6 +288,7 @@ static struct spi_driver tpm_tis_spi_driver = {
.pm = &tpm_tis_pm,
.of_match_table = of_match_ptr(of_tis_spi_match),
.acpi_match_table = ACPI_PTR(acpi_tis_spi_match),
+ .probe_type = PROBE_PREFER_ASYNCHRONOUS,
},
.probe = tpm_tis_spi_driver_probe,
.remove = tpm_tis_spi_remove,
--
2.27.0.111.gc72c7da667-goog
