From: Anton Vorontsov <avorontsov@ru•mvista.com>
To: Scott Wood <scottwood@freescale•com>
Cc: linuxppc-dev@ozlabs•org
Subject: Re: [PATCH 6/8] [POWERPC] sysdev,qe_lib: implement FSL GTM support
Date: Thu, 17 Apr 2008 19:07:55 +0400 [thread overview]
Message-ID: <20080417150755.GA29239@polina.dev.rtsoft.ru> (raw)
In-Reply-To: <20080417141903.GB21793@ld0162-tx32.am.freescale.net>
On Thu, Apr 17, 2008 at 09:19:03AM -0500, Scott Wood wrote:
> On Thu, Apr 17, 2008 at 04:52:35PM +0400, Anton Vorontsov wrote:
> > Heh. Scott, think about it. You have single 16bit timer with variable
> > frequency. To use it, you'd better know what exactly precision you need.
>
> Why? I know the timeout I need.
>
> > Then you limited to u16 for the interval for this chosen precision.
> >
> > Yes, you can implement this:
> >
> > #define MAX_PRESCALER (256 * 256 * 16)
> >
> > int gtm_reset_weird_behaving_utimer16(struct gtm_timer *tmr,
> > unsigned long long usec,
> > bool free_run)
> > {
> > int freq = 1000000;
> > int min_hz2 = (tmr->gtm->freq / MAX_PRESCALER) << 1;
> >
> > while (!(freq & 1) && !(usec & 1) && freq >= min_hz2) {
> > freq >>= 1;
> > usec >>= 1;
> > }
> >
> > if (usec > 0xffff)
> > return -EINVAL;
> >
> > return gtm_reset_ref_timer16(tmr, freq, (u16)usec, free_run);
> > }
>
> Try something like this:
>
> int gtm_reset_sane_behaving_timer(struct gtm_timer *tmr,
> u64 usec, bool free_run)
> {
> int freq = 1000000;
> int min_hz2 = (tmr->gtm->freq / MAX_PRESCALER) << 1;
>
> while (usec > 0xffff && freq >= min_hz2) {
This isn't a timer with usec precision! This is a timer that silently
crops precision as it wants to. Ahh, I see you dropped "u" prefix.
Well. I'm not going to use it anyway, so just give it some name you
prefer and I'll wrap it into the patch. Preferably, drop a line here with
kerneldoc for it, so I'll not have to document its drawbacks. :-)
> freq >>= 1;
> usec >>= 1;
> }
>
> if (usec > 0xffff)
> return -EINVAL;
>
> return gtm_reset_ref_timer16(tmr, freq, usec, free_run);
> }
>
> It could be made faster using cntlzw.
No need to cntlzw, there is fls() already. Though, here you'll need
two because of u64.
Btw, I hope you aware that single GTM timer running at 166MHz will give you
6 minutes of sleep, maximum. With cascaded timer you'll get much better
result of 310 days. Is that possible to use cascaded timer as a wakeup
event on 8313? If so, I'd suggest you to implement cascading firstly.
--
Anton Vorontsov
email: cbouatmailru@gmail•com
irc://irc.freenode.net/bd2
next prev parent reply other threads:[~2008-04-17 15:07 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-11 17:21 [PATCH 0/8] A bit of new code and sparse cleanups along the way Anton Vorontsov
2008-03-11 17:23 ` [PATCH 1/8] [POWERPC] fsl_elbc_nand: factor out localbus defines Anton Vorontsov
2008-04-11 14:06 ` Kumar Gala
2008-04-13 12:53 ` David Woodhouse
2008-04-14 15:10 ` Kumar Gala
2008-03-11 17:24 ` [PATCH 2/8] [POWERPC] fsl_lbc: implement few routines to manage FSL UPMs Anton Vorontsov
2008-04-11 14:09 ` Kumar Gala
2008-04-11 16:13 ` Anton Vorontsov
2008-04-11 16:18 ` Scott Wood
2008-04-11 17:03 ` Anton Vorontsov
2008-04-12 4:09 ` Paul Mackerras
2008-04-14 15:11 ` Kumar Gala
2008-03-11 17:24 ` [PATCH 3/8] [POWERPC] qe_lib: implement qe_muram_offset Anton Vorontsov
2008-03-18 17:48 ` Scott Wood
2008-04-14 15:11 ` Kumar Gala
2008-03-11 17:24 ` [PATCH 4/8] [POWERPC] immap_qe.h should include asm/io.h Anton Vorontsov
2008-04-14 15:11 ` Kumar Gala
2008-03-11 17:24 ` [PATCH 5/8] [POWERPC] qe_lib: export qe_get_brg_clk() Anton Vorontsov
2008-03-11 18:36 ` Kumar Gala
2008-03-11 18:44 ` Anton Vorontsov
2008-04-14 15:11 ` Kumar Gala
2008-03-11 17:24 ` [PATCH 6/8] [POWERPC] sysdev,qe_lib: implement FSL GTM support Anton Vorontsov
2008-03-18 17:43 ` Scott Wood
2008-03-18 19:21 ` Anton Vorontsov
2008-03-18 19:55 ` Scott Wood
2008-03-18 20:27 ` Anton Vorontsov
2008-03-18 20:48 ` Scott Wood
2008-04-16 18:39 ` Anton Vorontsov
2008-04-16 18:44 ` Scott Wood
2008-04-16 21:00 ` Anton Vorontsov
2008-04-16 21:58 ` Scott Wood
2008-04-17 12:52 ` Anton Vorontsov
2008-04-17 14:19 ` Scott Wood
2008-04-17 15:07 ` Anton Vorontsov [this message]
2008-04-17 16:14 ` Scott Wood
2008-04-17 16:43 ` Anton Vorontsov
2008-04-17 14:23 ` Laurent Pinchart
2008-04-17 15:13 ` Anton Vorontsov
2008-04-17 16:12 ` Anton Vorontsov
2008-04-08 9:01 ` Laurent Pinchart
2008-04-08 11:48 ` Anton Vorontsov
2008-03-11 17:24 ` [PATCH 7/8] [POWERPC] qe_lib: add support for QE USB Anton Vorontsov
2008-04-14 20:29 ` Kumar Gala
2008-03-11 17:24 ` [PATCH 8/8] [POWERPC] qe_io: fix sparse warnings Anton Vorontsov
2008-04-14 15:12 ` Kumar Gala
2008-04-14 15:14 ` [PATCH 0/8] A bit of new code and sparse cleanups along the way Kumar Gala
2008-04-14 17:49 ` Anton Vorontsov
-- strict thread matches above, loose matches on Subject: below --
2008-04-17 16:22 [PATCH 6/8] [POWERPC] sysdev,qe_lib: implement FSL GTM support Scott Wood
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