| Message ID | 20191108213257.3097633-17-arnd@arndb.de |
|---|---|
| State | Accepted |
| Commit | b98c7518c5345ac5f930fd40ce9d8d2b8dc2ba06 |
| Headers | show |
| Series | [01/16] staging: exfat: use prandom_u32() for i_generation | expand |
On Nov 08 Arnd Bergmann wrote: > 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. > > Reviewed-by: Clemens Ladisch <clemens@ladisch.de> > Cc: Stefan Richter <stefanr@s5r6.in-berlin.de> > Link: https://lore.kernel.org/lkml/20180711124923.1205200-1-arnd@arndb.de/ > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Committed to linux1394.git:for-next. Thank you for the patch and your extraordinary patience. > --- > 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 522f3addb5bd..33269316f111 100644 > --- a/drivers/firewire/ohci.c > +++ b/drivers/firewire/ohci.c > @@ -1752,7 +1752,7 @@ 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; > } -- Stefan Richter -======---== =-== -==-= http://arcgraph.de/sr/
diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c index 522f3addb5bd..33269316f111 100644 --- a/drivers/firewire/ohci.c +++ b/drivers/firewire/ohci.c @@ -1752,7 +1752,7 @@ 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; }
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. Reviewed-by: Clemens Ladisch <clemens@ladisch.de> Cc: Stefan Richter <stefanr@s5r6.in-berlin.de> Link: https://lore.kernel.org/lkml/20180711124923.1205200-1-arnd@arndb.de/ Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/firewire/ohci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.20.0