> -----Original Message----- > From: D, Lakshmi Sowjanya <lakshmi.sowjanya.d@xxxxxxxxx> > Sent: Wednesday, June 12, 2024 9:24 AM > To: tglx@xxxxxxxxxxxxx; giometti@xxxxxxxxxxxx; corbet@xxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; andriy.shevchenko@xxxxxxxxxxxxxxx; Dong, > Eddie <eddie.dong@xxxxxxxxx>; Hall, Christopher S > <christopher.s.hall@xxxxxxxxx>; N, Pandith <pandith.n@xxxxxxxxx>; Mohan, > Subramanian <subramanian.mohan@xxxxxxxxx>; T R, Thejesh Reddy > <thejesh.reddy.t.r@xxxxxxxxx>; D, Lakshmi Sowjanya > <lakshmi.sowjanya.d@xxxxxxxxx> > Subject: [PATCH v10 0/3] Add support for Intel PPS Generator > > From: Lakshmi Sowjanya D <lakshmi.sowjanya.d@xxxxxxxxx> > > The goal of the PPS (Pulse Per Second) hardware/software is to generate a > signal from the system on a wire so that some third-party hardware can observe > that signal and judge how close the system's time is to another system or piece > of hardware. > > Existing methods (like parallel ports) require software to flip a bit at just the right > time to create a PPS signal. Many things can prevent software from doing this > precisely. This (Timed I/O) method is better because software only "arms" the > hardware in advance and then depends on the hardware to "fire" and flip the > signal at just the right time. > > To generate a PPS signal with this new hardware, the kernel wakes up twice a > second, once for 1->0 edge and other for the 0->1 edge. It does this shortly > (~10ms) before the actual change in the signal needs to be made. It computes > the TSC value at which edge will happen, convert to a value hardware > understands and program this value to Timed I/O hardware. > The actual edge transition happens without any further action from the kernel. > > The result here is a signal coming out of the system that is roughly > 1,000 times more accurate than the old methods. If the system is heavily loaded, > the difference in accuracy is larger in old methods. > > Application Interface: > The API to use Timed I/O is very simple. It is enabled and disabled by writing a '1' > or '0' value to the sysfs enable attribute associated with the Timed I/O PPS > device. Each Timed I/O pin is represented by a PPS device. When enabled, a > pulse-per-second (PPS) synchronized with the system clock is continuously > produced on the Timed I/O pin, otherwise it is pulled low. > > The Timed I/O signal on the motherboard is enabled in the BIOS setup. > Intel Advanced Menu -> PCH IO Configuration -> Timed I/O <Enable> > > References: > https://en.wikipedia.org/wiki/Pulse-per-second_signal > https://drive.google.com/file/d/1vkBRRDuELmY8I3FlfOZaEBp-DxLW6t_V/view > https://youtu.be/JLUTT-lrDqw > > Patch 1 adds the pps(pulse per second) generator tio driver to the pps > subsystem. > Patch 2 documentation and usage of the pps tio generator module. > Patch 3 includes documentation for sysfs interface. > > These patches are based on the timers/core branch: > [1] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/?h=timers/core > These changes are dependent on patches that are merged in [1]. > > Please help to review the changes. > > Thanks in advance, > Sowjanya > > Changes from v2: > - Split patch 1 to remove the functions in later stages. > - Include required headers in pps_gen_tio. > > Changes from v3: > - Corrections in Documentation. > - Introducing non-RFC version of the patch series. > > Changes from v4: > - Setting id in ice_ptp > - Modified conversion logic in convert_base_to_cs. > - Included the usage of the APIs in the commit message of 2nd patch. > > Changes from v5: > - Change nsecs variable to use_nsecs. > - Change order of 1&2 patches and modify the commit message. > - Add sysfs abi file entry in MAINTAINERS file. > - Add check to find if any event is missed and disable hardware > accordingly. > > Changes from v6: > - Split patch 1 into 1&2 patches. > - Add check for overflow in convert_ns_to_cs(). > - Refine commit messages. > > Changes from v7: > - Split the if condition and return error if current time exceeds > expire time. > - Update kernel version and month in ABI file. > > Changes from v8: > - Add function to enable Timed I/O. > - Changed the updating of tio->enabled to a centralized place in > disable and enable functions. > > Changes from v9: > - use tio->enabled instead of reading ctrl register. > - change error code in enable_store to -ENODEV. > > Lakshmi Sowjanya D (3): > pps: generators: Add PPS Generator TIO Driver > Documentation: driver-api: pps: Add Intel Timed I/O PPS generator > ABI: pps: Add ABI documentation for Intel TIO > > .../ABI/testing/sysfs-platform-pps-tio | 7 + > Documentation/driver-api/pps.rst | 24 ++ > MAINTAINERS | 1 + > drivers/pps/generators/Kconfig | 16 ++ > drivers/pps/generators/Makefile | 1 + > drivers/pps/generators/pps_gen_tio.c | 264 ++++++++++++++++++ > 6 files changed, 313 insertions(+) > create mode 100644 Documentation/ABI/testing/sysfs-platform-pps-tio > create mode 100644 drivers/pps/generators/pps_gen_tio.c > > -- > 2.35.3 Hi, A gentle reminder for the review of the pps patchset. Regards Sowjanya
