Hi Miroslav,
Miroslav Lichvar writes:
> The PTP_SYS_OFFSET ioctl, which can be used to measure the offset
> between a PHC and the system clock, includes the total time that the
> gettime64 function of a driver needs to read the PHC timestamp.
>
> This typically involves reading of multiple PCI registers (sometimes in
> multiple iterations) and the register that contains the lowest bits of
> the timestamp is not read in the middle between the two readings of the
> system clock. This asymmetry causes the measured offset to have a
> significant error.
>
> Introduce a new ioctl, driver function, and helper functions, which
> allow the reading of the lowest register to be isolated from the other
> readings in order to reduce the asymmetry. The ioctl and driver function
> return three timestamps for each measurement:
> - system time right before reading the lowest bits of the PHC timestamp
> - PHC time
> - system time immediately after reading the lowest bits of the PHC
> timestamp
Cool stuff!
Just one little thing below. Feel free to add my ack to the series.
Acked-by: Vinicius Costa Gomes
>
> Cc: Richard Cochran
> Cc: Jacob Keller
> Signed-off-by: Miroslav Lichvar
> ---
> drivers/ptp/ptp_chardev.c| 39
> include/linux/ptp_clock_kernel.h | 26 +
> include/uapi/linux/ptp_clock.h | 12 ++
> 3 files changed, 77 insertions(+)
>
> diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
> index 2012551d93e0..1a04c437fd4f 100644
> --- a/drivers/ptp/ptp_chardev.c
> +++ b/drivers/ptp/ptp_chardev.c
> @@ -124,11 +124,13 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int
> cmd, unsigned long arg)
> struct ptp_clock_caps caps;
> struct ptp_clock_request req;
> struct ptp_sys_offset *sysoff = NULL;
> + struct ptp_sys_offset_extended *sysoff_extended = NULL;
> struct ptp_sys_offset_precise precise_offset;
> struct ptp_pin_desc pd;
> struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
> struct ptp_clock_info *ops = ptp->info;
> struct ptp_clock_time *pct;
> + struct ptp_system_timestamp sts;
> struct timespec64 ts;
> struct system_device_crosststamp xtstamp;
> int enable, err = 0;
> @@ -211,6 +213,43 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd,
> unsigned long arg)
> err = -EFAULT;
> break;
>
> + case PTP_SYS_OFFSET_EXTENDED:
> + if (!ptp->info->gettimex64) {
> + err = -EOPNOTSUPP;
> + break;
> + }
> + sysoff_extended = memdup_user((void __user *)arg,
> + sizeof(*sysoff_extended));
Looks like you forgot to free 'sysoff_extended', no?
--
Vinicius
