ARM: OMAP5: Fix warm reset with USB cable connected
Warm reset on OMAP5 freezes when USB cable is connected.
Fix requires PRM_RSTTIME.RSTTIME1 to be programmed
with the time for which reset should be held low for the
voltages and the oscillator to reach stable state.
There are 3 parameters to be considered for calculating
the time, which are mostly board and PMIC dependent.
-1- Time taken by the Oscillator to shut + restart
-2- PMIC OTP times
-3- Voltage rail ramp times, which inturn depends on the
PMIC slew rate and value of the voltage ramp needed.
In order to keep the code in u-boot simple, have a way
for boards to specify a pre computed time directly using
the 'CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC'
option. If boards fail to specify the time, use a default
as specified by 'CONFIG_DEFAULT_OMAP_RESET_TIME_MAX_USEC' instead.
Using the default value translates into some ~22ms and should work in
all cases.
However in order to avoid this large delay hiding other bugs,
its recommended that all boards look at their respective data
sheets and specify a pre computed and optimal value using
'CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC'
In order to help future board additions to compute this
config option value, add a README at doc/README.omap-reset-time
which explains how to compute the value. Also update the toplevel
README with the additional option and pointers to
doc/README.omap-reset-time.
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
[rnayak@ti.com: Updated changelog and added the README]
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
diff --git a/README b/README
index 0bc0af5..4531891 100644
--- a/README
+++ b/README
@@ -3323,6 +3323,10 @@
offset _bss_start_ofs from CONFIG_SYS_TEXT_BASE, rather than
directly. You should not need to touch this setting.
+- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
+ This is set by OMAP boards for the max time that reset should
+ be asserted. See doc/README.omap-reset-time for details on how
+ the value can be calulated on a given board.
The following definitions that deal with the placement and management
of environment data (variable area); in general, we support the