From: jon-hunter@ti•com (Jon Hunter)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 08/10] ARM: OMAP: Clean-up timer posted mode support
Date: Mon, 10 Sep 2012 16:59:36 -0500 [thread overview]
Message-ID: <504E62C8.8030100@ti.com> (raw)
In-Reply-To: <20120907222223.GQ1303@atomide.com>
On 09/07/2012 05:22 PM, Tony Lindgren wrote:
> * Jon Hunter <jon-hunter@ti•com> [120905 12:05]:
>> The dmtimer functions to read and write the dmtimer registers are currently
>> defined as follows ...
>>
>> static inline u32 __omap_dm_timer_read(struct omap_dm_timer *timer, u32 reg,
>> int posted);
>> static inline void __omap_dm_timer_write(struct omap_dm_timer *timer,
>> u32 reg, u32 val, int posted);
>>
>> The posted variable indicates if the timer is configured to use the posted mode
>> when performing register accesses. The posted mode configuration of the dmtimer
>> is stored in the omap_dm_timer structure that is also being passed to the above
>> functions and therefore we do not need to pass the posted variable separately.
>> Therefore, simplify the above functions by removing the posted variable as an
>> argument as this is not necessary.
>
> I believe the reason for passing the posted flag was to optimize out some
> functions from the timer code as that's being run all the time.
>
> Care to check the assembly before and after this patch for the timer
> functions with objdump -d to make sure it does not add tons of bloat
> there?
Hi Tony,
Thanks for the details here. I see that makes sense and that the
compiler could take advantage of this as the functions are inlined.
I have taken a look at the disassembled output using objdump as you
mentioned. What I see is ...
1. For dmtimer.c the impact appears negligible, the total number of
lines outputted by objdump only changed by 8 with (1215 lines) and
without (1207 lines) the patch applied.
2. For timer.c the impact is greater. I see that
omap2_gp_timer_set_next_event() increased by 6 instructions from 29
to 35. clocksource_read_cycles() increased by 2 instructions 15 to
17 instructions. dmtimer_read_sched_clock() increased by 2
instructions from 17 to 19. omap2_gp_timer_set_mode() increased by
21 instructions from 102 to 123.
I imagine that we are mainly concerned about
omap2_gp_timer_set_next_event(), clocksource_read_cycles() and
dmtimer_read_sched_clock() as these will be called often. Therefore, I
am not sure if you wish to drop this patch.
By the way, if we do drop this patch, I would then need to fix the
setting of the posted variable in mach-omap2/timer.c for clock-source in
the case where a dmtimer is used. Today the code assumes that for
clock-source and clock-events posted mode is always used. However, with
the errata i103/i767 we will disable posted mode for clock-source on
omap2/3/4/5/am33xx devices.
Cheers
Jon
next prev parent reply other threads:[~2012-09-10 21:59 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-05 19:04 [PATCH 00/10] ARM: OMAP: DMTIMER fixes and clean-up Jon Hunter
2012-09-05 19:04 ` [PATCH 01/10] ARM: OMAP3+: Implement timer workaround for errata i103 and i767 Jon Hunter
2012-09-06 5:07 ` Vaibhav Hiremath
2012-09-06 14:06 ` Jon Hunter
2012-09-06 14:42 ` Jon Hunter
2012-09-06 15:20 ` Jon Hunter
2012-09-13 10:26 ` Hiremath, Vaibhav
2012-09-13 10:24 ` Hiremath, Vaibhav
2012-09-05 19:04 ` [PATCH 02/10] ARM: OMAP: Fix timer posted mode support Jon Hunter
2012-09-06 12:57 ` Vaibhav Hiremath
2012-09-06 14:20 ` Jon Hunter
2012-09-06 16:01 ` Jon Hunter
2012-09-13 10:24 ` Hiremath, Vaibhav
2012-09-05 19:04 ` [PATCH 03/10] ARM: OMAP3: Correct HWMOD DMTIMER SYSC register declarations Jon Hunter
2012-09-05 19:04 ` [PATCH 04/10] ARM: OMAP2/3: Define HWMOD software reset status for DMTIMERs Jon Hunter
2012-09-05 19:04 ` [PATCH 05/10] ARM: OMAP2+: Don't use __omap_dm_timer_reset() Jon Hunter
2012-09-05 19:04 ` [PATCH 06/10] ARM: OMAP: Fix dmtimer reset for timer1 Jon Hunter
2012-09-05 19:04 ` [PATCH 07/10] ARM: OMAP: Clean-up dmtimer reset code Jon Hunter
2012-09-05 19:04 ` [PATCH 08/10] ARM: OMAP: Clean-up timer posted mode support Jon Hunter
2012-09-07 22:22 ` Tony Lindgren
2012-09-10 21:59 ` Jon Hunter [this message]
2012-09-11 0:58 ` Tony Lindgren
2012-09-11 16:26 ` Jon Hunter
2012-09-11 16:34 ` Tony Lindgren
2012-09-13 3:26 ` Jon Hunter
2012-09-05 19:04 ` [PATCH 09/10] ARM: OMAP: Add dmtimer interrupt disable function Jon Hunter
2012-09-06 12:58 ` Vaibhav Hiremath
2012-09-06 14:26 ` Jon Hunter
2012-09-05 19:04 ` [PATCH 10/10] ARM: OMAP: Remove unnecessary call to clk_get() Jon Hunter
2012-09-06 12:58 ` [PATCH 00/10] ARM: OMAP: DMTIMER fixes and clean-up Vaibhav Hiremath
2012-09-06 14:30 ` Jon Hunter
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=504E62C8.8030100@ti.com \
--to=jon-hunter@ti$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox