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    ARM: OMAP4: Workaround the OCP synchronisation issue with 32K synctimer. · 68523f42
    Santosh Shilimkar 提交于
    On OMAP4, recently a synchronisation bug is discovered by hardware
    team, which leads to incorrect timer value read from 32K sync timer
    IP when the IP is comming out of idle.
    
    The issue is due to the synchronization methodology used in the SYNCTIMER IP.
    The value of the counter register in 32kHz domain is synchronized to the OCP
    domain register only at count up event, and if the OCP clock is switched off,
    the OCP register gets out of synch until the first count up event after the
    clock is switched back -at the next falling edge of the 32kHz clock.
    
    Further investigation revealed that it applies to gptimer1 and watchdog timer2
    as well which may run on 32KHz. This patch fixes the issue for all the
    applicable modules.
    
    The BUG has not made it yet to the OMAP errata list and it is applicable to
    OMAP1/2/3/4/5. OMAP1/2/3 it is taken care indirectly by autodeps.
    
    By enabling static depedency of wakeup clockdomain with MPU, as soon as MPU
    is woken up from lowpower state(idle) or whenever MPU is active, PRCM forces
    the OCP clock to be running and allow the counter value to be updated properly
    in the OCP clock domain.
    
    The bug is going to fixed in future OMAP versions.
    
    Reported-Tested-by: dave.long@linaro.org
    [dave.long@linaro.org: Reported the oprofile time stamp issue with synctimer
    and helped to test this patch]
    Signed-off-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
    Signed-off-by: NKevin Hilman <khilman@ti.com>
    68523f42
pm44xx.c 6.9 KB