Messages in this thread | | | Date | Mon, 3 Jul 2023 11:32:05 +0200 | Subject | Re: [PATCH 1/5] pps: add pulse-width calculation in nsec | From | Rodolfo Giometti <> |
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On 02/07/23 14:20, Farber, Eliav wrote: > On 6/27/2023 5:27 PM, Rodolfo Giometti wrote: >> On 25/06/23 16:21, Eliav Farber wrote: >>> This change adds PPS pulse-width calculation in nano seconds. >>> Width time can be calculated for both assert time and reset time. >>> >>> Calculation can be done only if capture ASSERT and capture CLEAR modes >>> are both enabled. >>> >>> Assert width is calculated as: >>> clear-time - assert-time >>> and clear width is calculated as: >>> assert-time - clear-time >>> >>> Read-only sysfs were added to get the last pulse-width time and event >>> sequence. >>> Examples: >>> * cat /sys/class/pps/pps0/pulse_width_assert >>> 20001450#85 >>> * cat /sys/class/pps/pps1/pulse_width_clear >>> 979893314#16 >>> >>> Signed-off-by: Eliav Farber <farbere@amazon.com> >>> --- >>> drivers/pps/kapi.c | 49 ++++++++++++++++++++++++++++++++++++++ >>> drivers/pps/pps.c | 9 +++++++ >>> drivers/pps/sysfs.c | 30 +++++++++++++++++++++++ >>> include/linux/pps_kernel.h | 3 +++ >>> include/uapi/linux/pps.h | 19 +++++++++++++++ >>> 5 files changed, 110 insertions(+) >>> >>> diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c >>> index d9d566f70ed1..deeecfc0a3ee 100644 >>> --- a/drivers/pps/kapi.c >>> +++ b/drivers/pps/kapi.c >>> @@ -82,6 +82,14 @@ struct pps_device *pps_register_source(struct >>> pps_source_info *info, >>> goto pps_register_source_exit; >>> } >>> >>> + if ((info->mode & PPS_WIDTHBOTH) && >>> + ((info->mode & PPS_CAPTUREBOTH) != PPS_CAPTUREBOTH)) { >>> + pr_err("%s: width can't be calculated without both captures >>> (mode = 0x%x)\n", >>> + info->name, info->mode); >>> + err = -EINVAL; >>> + goto pps_register_source_exit; >>> + } >> >> See the comment below where you define PPS_WIDTHBOTH. >> >>> /* Allocate memory for the new PPS source struct */ >>> pps = kzalloc(sizeof(struct pps_device), GFP_KERNEL); >>> if (pps == NULL) { >>> @@ -143,6 +151,39 @@ void pps_unregister_source(struct pps_device *pps) >>> } >>> EXPORT_SYMBOL(pps_unregister_source); >>> >>> +static u64 pps_ktime_sub(struct pps_ktime *ts1, struct pps_ktime *ts2) >>> +{ >>> + if (ts1->sec == ts2->sec) >>> + return (ts1->nsec > ts2->nsec) ? (ts1->nsec - ts2->nsec) : >>> (ts2->nsec - ts1->nsec); >>> + >>> + if (ts1->sec > ts2->sec) >>> + return (ts1->sec - ts2->sec) * NSEC_PER_SEC + ts1->nsec - >>> ts2->nsec; >>> + >>> + return (ts2->sec - ts1->sec) * NSEC_PER_SEC + ts2->nsec - ts1->nsec; >>> +} >>> + >>> +static void pps_calc_clear_width(struct pps_device *pps) >>> +{ >>> + if (pps->clear_sequence == 0) >>> + return; >>> + >>> + pps->clear_width.sequence++; >> >> I don't understand the meaning of this field... regarding assert and clear it >> states the n-th sample but in this case...? Why do you need it? > > For assert and clear, the sequence parameter is basically the counter > of assert/clear events. > Similarly, I wanted to have a counter for the number of pulses which > there width was counted. > The sequence was used by me in the sysfs to show the pulse counter and > pulse width in nano-seconds. > Will counter make more sense instead of sequence? > Initially, I used the assert_sequence and clear_sequence as the pulse > counter, but there were few cases to handle. > In case first interrupt happened during a pulse, then > assert_sequence != clear_sequence, but if not then > assert_sequence == clear_sequence. > So I preferred to add an new independent value.
OK.
>>> + pps->clear_width.nsec = pps_ktime_sub(&pps->assert_tu, &pps->clear_tu); >>> + dev_dbg(pps->dev, "PPS clear width = %llu#%u\n", >>> + pps->clear_width.nsec, pps->clear_width.sequence); >>> +} >>> + >>> +static void pps_calc_assert_width(struct pps_device *pps) >>> +{ >>> + if (pps->assert_sequence == 0) >>> + return; >>> + >>> + pps->assert_width.sequence++; >> >> Ditto. >> >>> + pps->assert_width.nsec = pps_ktime_sub(&pps->clear_tu, &pps->assert_tu); >>> + dev_dbg(pps->dev, "PPS assert width = %llu#%u\n", >>> + pps->assert_width.nsec, pps->assert_width.sequence); >>> +} >>> + >>> /* pps_event - register a PPS event into the system >>> * @pps: the PPS device >>> * @ts: the event timestamp >>> @@ -191,6 +232,10 @@ void pps_event(struct pps_device *pps, struct >>> pps_event_time *ts, int event, >>> dev_dbg(pps->dev, "capture assert seq #%u\n", >>> pps->assert_sequence); >>> >>> + /* Calculate clear pulse-width */ >>> + if (pps->params.mode & PPS_WIDTHCLEAR) >>> + pps_calc_clear_width(pps); >>> + >>> captured = ~0; >>> } >>> if (event & pps->params.mode & PPS_CAPTURECLEAR) { >>> @@ -205,6 +250,10 @@ void pps_event(struct pps_device *pps, struct >>> pps_event_time *ts, int event, >>> dev_dbg(pps->dev, "capture clear seq #%u\n", >>> pps->clear_sequence); >>> >>> + /* Calculate assert pulse-width */ >>> + if (pps->params.mode & PPS_WIDTHASSERT) >>> + pps_calc_assert_width(pps); >>> + >>> captured = ~0; >>> } >>> >>> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c >>> index 5d19baae6a38..8299a272af11 100644 >>> --- a/drivers/pps/pps.c >>> +++ b/drivers/pps/pps.c >>> @@ -195,6 +195,11 @@ static long pps_cdev_ioctl(struct file *file, >>> fdata.info.clear_tu = pps->clear_tu; >>> fdata.info.current_mode = pps->current_mode; >>> >>> + memcpy(&fdata.info.assert_width, &pps->assert_width, >>> + sizeof(struct pps_kwidth)); >>> + memcpy(&fdata.info.clear_width, &pps->clear_width, >>> + sizeof(struct pps_kwidth)); >>> + >>> spin_unlock_irq(&pps->lock); >>> >>> err = copy_to_user(uarg, &fdata, sizeof(struct pps_fdata)); >>> @@ -283,6 +288,10 @@ static long pps_cdev_compat_ioctl(struct file *file, >>> sizeof(struct pps_ktime_compat)); >>> memcpy(&compat.info.clear_tu, &pps->clear_tu, >>> sizeof(struct pps_ktime_compat)); >>> + memcpy(&compat.info.assert_width, &pps->assert_width, >>> + sizeof(struct pps_kwidth_compat)); >>> + memcpy(&compat.info.clear_width, &pps->clear_width, >>> + sizeof(struct pps_kwidth_compat)); >>> >>> spin_unlock_irq(&pps->lock); >>> >>> diff --git a/drivers/pps/sysfs.c b/drivers/pps/sysfs.c >>> index 134bc33f6ad0..3e34de77dba6 100644 >>> --- a/drivers/pps/sysfs.c >>> +++ b/drivers/pps/sysfs.c >>> @@ -79,6 +79,34 @@ static ssize_t path_show(struct device *dev, struct >>> device_attribute *attr, >>> } >>> static DEVICE_ATTR_RO(path); >>> >>> +static ssize_t pulse_width_assert_show(struct device *dev, >>> + struct device_attribute *attr, >>> + char *buf) >>> +{ >>> + struct pps_device *pps = dev_get_drvdata(dev); >>> + >>> + if (!(pps->info.mode & PPS_WIDTHASSERT)) >>> + return 0; >>> + >>> + return sprintf(buf, "%llu#%u\n", >>> + pps->assert_width.nsec, pps->assert_width.sequence); >>> +} >>> +static DEVICE_ATTR_RO(pulse_width_assert); >>> + >>> +static ssize_t pulse_width_clear_show(struct device *dev, >>> + struct device_attribute *attr, >>> + char *buf) >>> +{ >>> + struct pps_device *pps = dev_get_drvdata(dev); >>> + >>> + if (!(pps->info.mode & PPS_WIDTHCLEAR)) >>> + return 0; >>> + >>> + return sprintf(buf, "%llu#%u\n", >>> + pps->clear_width.nsec, pps->clear_width.sequence); >>> +} >>> +static DEVICE_ATTR_RO(pulse_width_clear); >>> + >>> static struct attribute *pps_attrs[] = { >>> &dev_attr_assert.attr, >>> &dev_attr_clear.attr, >>> @@ -86,6 +114,8 @@ static struct attribute *pps_attrs[] = { >>> &dev_attr_echo.attr, >>> &dev_attr_name.attr, >>> &dev_attr_path.attr, >>> + &dev_attr_pulse_width_assert.attr, >>> + &dev_attr_pulse_width_clear.attr, >>> NULL, >>> }; >>> >>> diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h >>> index 78c8ac4951b5..15f2338095c6 100644 >>> --- a/include/linux/pps_kernel.h >>> +++ b/include/linux/pps_kernel.h >>> @@ -51,6 +51,9 @@ struct pps_device { >>> struct pps_ktime clear_tu; >>> int current_mode; /* PPS mode at event time */ >>> >>> + struct pps_kwidth assert_width; /* PPS assert pulse-width time >>> and event seq # */ >>> + struct pps_kwidth clear_width; /* PPS clear pulse-width time >>> and event seq # */ >>> + >>> unsigned int last_ev; /* last PPS event id */ >>> wait_queue_head_t queue; /* PPS event queue */ >>> >>> diff --git a/include/uapi/linux/pps.h b/include/uapi/linux/pps.h >>> index 009ebcd8ced5..dd93dac0afc1 100644 >>> --- a/include/uapi/linux/pps.h >>> +++ b/include/uapi/linux/pps.h >>> @@ -64,12 +64,24 @@ struct pps_ktime_compat { >>> } __attribute__((packed, aligned(4))); >>> #define PPS_TIME_INVALID (1<<0) /* used to specify timeout==NULL */ >>> >>> +struct pps_kwidth { >>> + __u64 nsec; >>> + __u32 sequence; >>> +}; >>> + >>> +struct pps_kwidth_compat { >>> + __u64 nsec; >>> + __u32 sequence; >>> +} __attribute__((packed, aligned(4))); >> >> Why do you need a new type? Since both assert_width and clear_width are time >> quantities as far as assert_tu and clear_tu, they can be of the same type, can't >> they? Or, at least they can simply be __u64 since having an assert_width or >> clear_width longer than 1 second is a non-sense... > > For each pulse I wanted to save width in nsec (without sec) and > counter. > I need it twice for both assert and clear, hence I added a new > structure for it.
I see, but I prefere you do as in struct pps_kinfo where times are times and sequence numbers are numbers, and not mixing them.
>>> struct pps_kinfo { >>> __u32 assert_sequence; /* seq. num. of assert event */ >>> __u32 clear_sequence; /* seq. num. of clear event */ >>> struct pps_ktime assert_tu; /* time of assert event */ >>> struct pps_ktime clear_tu; /* time of clear event */ >>> int current_mode; /* current mode bits */ >>> + struct pps_kwidth assert_width; /* assert pulse-width time and seq. >>> num. */ >>> + struct pps_kwidth clear_width; /* clear pulse-width time and seq. num. */ >>> }; >> >> Altering this structure may break userspace code... also rfc2783 at section-3.2 >> states that: >> >> The API defines these new data structures: >> >> typedef struct { >> pps_seq_t assert_sequence; /* assert event seq # */ >> pps_seq_t clear_sequence; /* clear event seq # */ >> pps_timeu_t assert_tu; >> pps_timeu_t clear_tu; >> int current_mode; /* current mode bits */ >> } pps_info_t; >> >> So, I'm not willing to change this structure just to add this new data that I >> don't even know where it's used... >> >> If you just read these information via sysfs, please drop these part. > > ACK. I'll drop this part. > >>> struct pps_kinfo_compat { >>> @@ -78,6 +90,8 @@ struct pps_kinfo_compat { >>> struct pps_ktime_compat assert_tu; /* time of assert event */ >>> struct pps_ktime_compat clear_tu; /* time of clear event */ >>> int current_mode; /* current mode bits */ >>> + struct pps_kwidth_compat assert_width; /* assert pulse-width time and >>> seq. num. */ >>> + struct pps_kwidth_compat clear_width; /* clear pulse-width time and >>> seq. num. */ >>> }; >>> >>> struct pps_kparams { >>> @@ -96,6 +110,11 @@ struct pps_kparams { >>> #define PPS_CAPTURECLEAR 0x02 /* capture clear events */ >>> #define PPS_CAPTUREBOTH 0x03 /* capture assert and clear >>> events */ >>> >>> +/* Pulse-width calculation */ >>> +#define PPS_WIDTHASSERT 0x04 /* calculate assert width */ >>> +#define PPS_WIDTHCLEAR 0x08 /* calculate clear width */ >>> +#define PPS_WIDTHBOTH 0x0c /* calculate assert and clear >>> width */ >>> + >> >> I don't understand why a process should ask for just PPS_WIDTHASSERT or >> PPS_WIDTHCLEAR... I think you can avoid defining these values and just enabling >> pulse width calculation when both assert and clear events are available. > > ACK. I'll drop the new defines and enable width calculation when > PPS_CAPTUREASSERT and PPS_CAPTURECLEAR are both defined. > >>> #define PPS_OFFSETASSERT 0x10 /* apply compensation for assert event */ >>> #define PPS_OFFSETCLEAR 0x20 /* apply compensation for clear >>> event */ >> >> However, the real point is: since an userpsace program can retrieve the time of >> assert and clear events, why it cannot compute the pulses width by itself? :) > > The userpsace program can retrieve the time of assert and clear events, > but it is not always clear how to compute it. > Initially that was how I did it: > Read both times, make sure sequence of both times was identical, and > then compute: clear_time – assert_time. > But as I mentioned, when using wide pulses, it might be that when > driver starts, it is a the middle of a pulse. > In that case clear_time will be captured first (seq #1). > Then assert_time is captured (seq #1). > However, assert pulse width can only be calculated for the second > clear-time sequence and first assert-time sequence. > So to simplify this for the user, I added the calculation to the > driver. > Hope this was clear. > Please let me know if this satisfies you, and then I’ll share a second > version of patches which fixes all the other comments you gave.
Mmm... kernel drivers should implement mechanisms and not policies and since RFC2783 doesn't state this computation I think you are implementing a policy.
Let me suggest to add this piece of code to the pps-utils (maybe within the ppstest.c utility).
Ciao,
Rodolfo
-- GNU/Linux Solutions e-mail: giometti@enneenne.com Linux Device Driver giometti@linux.it Embedded Systems phone: +39 349 2432127 UNIX programming skype: rodolfo.giometti
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