xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

ptp: add PTP_SYS_OFFSET_EXTENDED ioctl

Browse Source 
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
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 returns 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

Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Jacob Keller <jacob.e.keller@intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Miroslav Lichvar
2018-11-09 11:14:44 +01:00
committed by David S. Miller
parent 83d0bdc739
commit 361800876f
3 changed files with 76 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
include/uapi/linux/ptp_clock.h
View File

@@ -84,6 +84,16 @@ struct ptp_sys_offset {
struct ptp_clock_time ts[2 * PTP_MAX_SAMPLES + 1];
};
struct ptp_sys_offset_extended {
unsigned int n_samples; /* Desired number of measurements. */
unsigned int rsv[3]; /* Reserved for future use. */
/*
* Array of [system, phc, system] time stamps. The kernel will provide
* 3*n_samples time stamps.
*/
struct ptp_clock_time ts[PTP_MAX_SAMPLES][3];
};
struct ptp_sys_offset_precise {
struct ptp_clock_time device;
struct ptp_clock_time sys_realtime;
@@ -136,6 +146,8 @@ struct ptp_pin_desc {
#define PTP_PIN_SETFUNC _IOW(PTP_CLK_MAGIC, 7, struct ptp_pin_desc)
#define PTP_SYS_OFFSET_PRECISE \
_IOWR(PTP_CLK_MAGIC, 8, struct ptp_sys_offset_precise)
#define PTP_SYS_OFFSET_EXTENDED \
_IOW(PTP_CLK_MAGIC, 9, struct ptp_sys_offset_extended)
struct ptp_extts_event {
struct ptp_clock_time t; /* Time event occured. */