From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: y2038@lists.linaro.org, linux-kernel@vger.kernel.org,
Clemens Ladisch <clemens@ladisch.de>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Richard Fontana <rfontana@redhat.com>,
linux1394-devel@lists.sourceforge.net
Subject: Re: [PATCH 16/16] firewire: ohci: stop using get_seconds() for BUS_TIME
Date: Wed, 13 Nov 2019 21:04:37 +0100 [thread overview]
Message-ID: <20191113210437.323f9acd@kant> (raw)
In-Reply-To: <20191108213257.3097633-17-arnd@arndb.de>
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/
prev parent reply other threads:[~2019-11-13 20:05 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-08 21:32 [PATCH 00/16] drivers: y2038 updates Arnd Bergmann
2019-11-08 21:32 ` [PATCH 01/16] staging: exfat: use prandom_u32() for i_generation Arnd Bergmann
2019-11-08 21:53 ` Valdis Klētnieks
2019-11-08 21:32 ` [PATCH 02/16] fat: " Arnd Bergmann
2019-11-08 21:32 ` [PATCH 03/16] net: sock: use __kernel_old_timespec instead of timespec Arnd Bergmann
2019-11-09 19:09 ` Deepa Dinamani
2019-11-08 21:32 ` [PATCH 04/16] dlm: use SO_SNDTIMEO_NEW instead of SO_SNDTIMEO_OLD Arnd Bergmann
2019-11-09 19:14 ` Deepa Dinamani
2019-11-08 21:32 ` [PATCH 05/16] xtensa: ISS: avoid struct timeval Arnd Bergmann
2019-11-08 21:38 ` Max Filippov
2019-11-08 21:32 ` [PATCH 06/16] um: ubd: use 64-bit time_t where possible Arnd Bergmann
2019-11-08 21:32 ` [PATCH 07/16] acct: stop using get_seconds() Arnd Bergmann
2019-11-08 21:32 ` [PATCH 08/16] tsacct: add 64-bit btime field Arnd Bergmann
2019-11-08 21:32 ` [PATCH 09/16] netfilter: nft_meta: use 64-bit time arithmetic Arnd Bergmann
2019-11-09 11:20 ` Phil Sutter
2019-11-15 22:44 ` Pablo Neira Ayuso
2019-11-08 21:32 ` [PATCH 10/16] packet: clarify timestamp overflow Arnd Bergmann
2019-11-08 21:32 ` [PATCH 11/16] quota: avoid time_t in v1_disk_dqblk definition Arnd Bergmann
2019-11-08 21:32 ` [PATCH 12/16] hostfs: pass 64-bit timestamps to/from user space Arnd Bergmann
2019-11-20 20:30 ` [Y2038] " Ben Hutchings
2019-11-20 20:35 ` Ben Hutchings
2019-11-08 21:32 ` [PATCH 13/16] hfs/hfsplus: use 64-bit inode timestamps Arnd Bergmann
2019-11-13 3:53 ` Ernesto A. Fernández
2019-11-13 5:59 ` Viacheslav Dubeyko
2019-11-13 8:06 ` [Y2038] " Arnd Bergmann
2019-11-13 17:03 ` Viacheslav Dubeyko
2019-11-08 21:32 ` [PATCH 14/16] drm/msm: avoid using 'timespec' Arnd Bergmann
2019-11-12 16:55 ` Jordan Crouse
2019-11-08 21:32 ` [PATCH 15/16] drm/etnaviv: use ktime_t for timeouts Arnd Bergmann
2019-11-08 23:03 ` Lucas Stach
2019-11-09 12:12 ` Arnd Bergmann
2019-11-11 9:55 ` Lucas Stach
2019-11-11 16:24 ` Arnd Bergmann
2019-11-08 21:32 ` [PATCH 16/16] firewire: ohci: stop using get_seconds() for BUS_TIME Arnd Bergmann
2019-11-13 20:04 ` Stefan Richter [this message]
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