platform/chrome: cros_ec_spi: Set PROBE_PREFER_ASYNCHRONOUS

This driver often takes on the order of 10ms to start, but in some cases
as much as 600ms [1]. It shouldn't have many cross-device dependencies
to race with, nor racy access to shared state with other drivers, so
this should be a relatively low risk change.

This driver was pinpointed as part of a survey of top slowest initcalls
(i.e., are built in, and probing synchronously) on a lab of ChromeOS
systems.

[1] 600ms was especially surprising to me, so I checked a little deeper.
This driver is used to interface with Embedded Controllers besides just
the traditional laptop power-state controller -- it also interfaces with
some fingerprint readers, which may start up in parallel with the
kernel, or which may not even be present on some SKUs, despite having a
node for it. Thus, our time is wasted just timing out talking to it. At
least we can do that without blocking everyone else.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20221101152132.v2.5.Ia458a69e1d592bfa4f04cde7018bbc7486f91a23@changeid

diff --git a/drivers/platform/chrome/cros_ec_spi.c b/drivers/platform/chrome/cros_ec_spi.c
index 7360b3ff6e4fc8f5f48821aa15c9b99a48947f14..21143dba8970472890cee4f91f305035552952a5 100644 (file)
--- a/drivers/platform/chrome/cros_ec_spi.c
+++ b/drivers/platform/chrome/cros_ec_spi.c
@@ -834,6 +834,7 @@ static struct spi_driver cros_ec_driver_spi = {
                .name   = "cros-ec-spi",
                .of_match_table = cros_ec_spi_of_match,
                .pm     = &cros_ec_spi_pm_ops,
+               .probe_type = PROBE_PREFER_ASYNCHRONOUS,
        },
        .probe          = cros_ec_spi_probe,
        .remove         = cros_ec_spi_remove,