* Grygorii Strashko [off-list ref] [160412 11:31]:

On 04/12/2016 07:04 PM, Tony Lindgren wrote:

quoted

* Grygorii Strashko [off-list ref] [160412 03:44]:

quoted

The commit 55ee7017ee31 ("arm: omap2: board-generic: use
omap4_local_timer_init for AM437x") unintentionally changes the
clocksource devices for AM437x from OMAP GP Timer to SyncTimer32K.

Unfortunately, the SyncTimer32K is starving from frequency deviation
as mentioned in commit 5b5c01359152 ("ARM: OMAP2+: AM43x: Use gptimer
as clocksource") and, as reported by Franklin [1], even its monotonic
nature is under question (most probably there is a HW issue, but it's
still under investigation).

Taking into account above facts It's reasonable to rollback to the use
of omap3_gptimer_timer_init().

I thought only the ePOS EVM does not have the 32k clock available?
Maybe this is the the old sync timer autocorrection drift issue?

May be, as i mentioned in [1] it could be errata same as for Watchdog
Advisory 22 (or OMAP_TIMER_ERRATA_I103_I767).

But as per commit 5b5c01359152 ("ARM: OMAP2+: AM43x: Use gptimer
as clocksource") there is no reason to use SyncTimer32K as
clocksource any way (not only on epos):

commit 5b5c01359152f3ddaa1aa0e5d1141bc2b29ba2c5
Author: Rajendra Nayak [off-list ref]
Date:   Fri Feb 7 15:51:26 2014 +0530

    ARM: OMAP2+: AM43x: Use gptimer as clocksource
    
    The SyncTimer in AM43x is clocked using the following two sources:
    1) An inaccuarte 32k clock (CLK_32KHZ) derived from PER DPLL, causing system
       time to go slowly (~10% deviation).
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2) external 32KHz RTC clock, which may not always be available on board like
       in the case of ePOS EVM

This sounds similar to recent "ARM: dts: dra7: Correct clock tree for
sys_32k_ck", can you see if similar changes help for am43x?

Regards,

Tony