Date: Mon, 19 Aug 2019 08:26:42 -0600 From: Ian Lepore <ian@freebsd.org> To: "O'Connor, Daniel" <darius@dons.net.au> Cc: "usb@freebsd.org" <usb@FreeBSD.org>, "freebsd-arm@FreeBSD.org" <freebsd-arm@FreeBSD.org> Subject: Re: Is it a good idea to use a usb-serial adapter for PPS input? Yes, it is. Message-ID: <fc1ef92211cfc9aeff3b4bd4335d69ceda5e5223.camel@freebsd.org> In-Reply-To: <9E142F1A-5E8C-4410-91F5-7C80B3D0A15B@dons.net.au> References: <f1d765814f722fb2c99c9870b3cc2607b4eca2d7.camel@freebsd.org> <B9EFA4D4-C1AD-4181-B421-F6BD53434FA5@dons.net.au> <bfd784f6ac9c939dbe6a243336bc3b6eab02d4f5.camel@freebsd.org> <61B1AAF3-40F6-47BC-8F05-7491C13BF288@dons.net.au> <9E142F1A-5E8C-4410-91F5-7C80B3D0A15B@dons.net.au>
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On Mon, 2019-08-19 at 17:09 +0930, O'Connor, Daniel wrote:
> > On 12 Aug 2019, at 09:09, O'Connor, Daniel <darius@dons.net.au>
> > wrote:
> > > always get lost on single-core processors which are in cpu_idle()
> > > at
> > > the time the hardclock interrupt happens. (But that's fixable by
> > > just
> > > increasing the number of timehands, I think at least 4 are
> > > required.)
> >
> > OK, how do I increase the number of clock hands?
>
> I am going to try this diff but buildkernel is going to take a
> while...
>
> diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
> index 2656fb4d2..00440b6a2 100644
> --- a/sys/kern/kern_tc.c
> +++ b/sys/kern/kern_tc.c
> @@ -83,8 +83,48 @@ struct timehands {
> struct timehands *th_next;
> };
>
> -static struct timehands th0;
> +static struct timehands th2;
> static struct timehands th1 = {
> + .th_next = &th2
> +};
> +
> +static struct timehands th3;
> +static struct timehands th2 = {
> + .th_next = &th3
> +};
> +
> +static struct timehands th4;
> +static struct timehands th3 = {
> + .th_next = &th4
> +};
> +
> +static struct timehands th5;
> +static struct timehands th4 = {
> + .th_next = &th5
> +};
> +
> +static struct timehands th6;
> +static struct timehands th5 = {
> + .th_next = &th6
> +};
> +
> +static struct timehands th7;
> +static struct timehands th6 = {
> + .th_next = &th7
> +};
> +
> +static struct timehands th8;
> +static struct timehands th7 = {
> + .th_next = &th8
> +};
> +
> +static struct timehands th9;
> +static struct timehands th8 = {
> + .th_next = &th9
> +};
> +
> +static struct timehands th0;
> +static struct timehands th9 = {
> .th_next = &th0
> };
> static struct timehands th0 = {
>
Oh, I'm sorry, I forgot to respond about this. Yeah, that patch would
do it. I think a minimum of 4 sets of timehands are needed for pps
capture on a single-core system with a latching timecounter like
dmtpps.
-- Ian
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