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    Subject[PATCH] firewire: ohci: stop using get_seconds() for BUS_TIME
    Date
    The ohci driver uses the get_seconds() function to implement the 32-bit
    CSR_BUS_TIME register. This was added in 2010 commit a48777e03ad5
    ("firewire: add CSR BUS_TIME support").

    As get_seconds() returns a 32-bit value (on 32-bit architectures), it
    seems like a good fit for that register, but it is also deprecated because
    of the y2038/y2106 overflow problem, and should be replaced throughout
    the kernel with either ktime_get_real_seconds() or ktime_get_seconds().

    I'm using the latter here, which uses monotonic time. This has the
    advantage of behaving better during concurrent settimeofday() updates
    or leap second adjustments and won't overflow a 32-bit integer, but
    the downside of using CLOCK_MONOTONIC instead of CLOCK_REALTIME is
    that the observed values are not related to external clocks.

    If we instead need UTC but can live with clock jumps or overflows,
    then we should use ktime_get_real_seconds() instead, retaining the
    existing behavior.

    Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    ---
    drivers/firewire/ohci.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
    index 45c048751f3b..5125841ea338 100644
    --- a/drivers/firewire/ohci.c
    +++ b/drivers/firewire/ohci.c
    @@ -1765,7 +1765,7 @@ static u32 update_bus_time(struct fw_ohci *ohci)

    if (unlikely(!ohci->bus_time_running)) {
    reg_write(ohci, OHCI1394_IntMaskSet, OHCI1394_cycle64Seconds);
    - ohci->bus_time = (lower_32_bits(get_seconds()) & ~0x7f) |
    + ohci->bus_time = (lower_32_bits(ktime_get_seconds()) & ~0x7f) |
    (cycle_time_seconds & 0x40);
    ohci->bus_time_running = true;
    }
    --
    2.9.0
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