tree 8b31c9d7f234be010c3102981f88afbba40e067d
parent 54e28fed8ac029b884da1cf652ad24601eee2d8e
author Mark Salyzyn <salyzyn@google.com> 1589398752 -0700
committer Mark Salyzyn <salyzyn@google.com> 1589574558 -0700

recovery: fastbootd: retry opening graphics

Recovery and fastbootd hardening.

With GKI we find in certain situations the timing of the drivers
loading is delayed as compared to a monolithic kernel.  This
exasperates an existing race where during second stage init, the
graphics driver might not have completely instantiated by the time
fastboot or recovery menu ui is being set up.

To address this, we call gr_init() every 10ms until either 5 seconds
timeout or success.  If we timeout, there will be no TUI (minui), but
this is better than if we just tried once and dropped the TUI and was
effectively running headless.  5 seconds timeout is arbitrary, based
on the default in init for wait for file; but makes sense as any
longer will impact flashstation and fastboot flashall enough to be
a cause for consternation.

It should be noted that both recovery and fastbootd can still service
adb or fastboot gadgets headless.  For instance if the device tree is
misconfigured as a permanent issue that would head for the timeout.
Prefering to give up after a timeout so that device can be flashed by
fastbootd, or rebooted by recovery adbd, over the protocol is
advantageous for tool stability.

Architectural Concern:

The graphics driver, if not well written, may panic the kernel if we
try to access it too soon while it is probing.  On such devices it
will be necessary to hold off in 'on init' or 'on early-init' phases
until the graphics drivers have completely probed.  Or better yet,
fix the driver.  This problem would happen in any case occasionally
even without this adjustments, but could conceivably be amplified by
the loop trying to open the graphics device.

Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 151950334
Test: make sure user space fastbootd comes up reliably for a GKI kernel
Change-Id: I1ce31a01544a58cdf7b9d657c1146bee77894e46