On Fri, Jun 19, 2020 at 02:20:01PM -0700, Douglas Anderson wrote:
> 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
>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
/Jarkko
