From: George Cherian <george.cherian@ti.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
linux-omap@vger.kernel.org, davem@davemloft.net,
jeffrey.t.kirsher@intel.com, dborkman@redhat.com,
ast@plumgrid.com, tklauser@distanz.ch, mpa@pengutronix.de,
bhutchings@solarflare.com, zonque@gmail.com, balbi@ti.com,
mugunthanvnm@ti.com, t-kristo@ti.com, mturquette@linaro.org,
linux@arm.linux.org.uk, galak@codeaurora.org,
ijc+devicetree@hellion.org.uk, mark.rutland@arm.com,
pawel.moll@arm.com, robh+dt@kernel.org, tony@atomide.com,
bcousson@baylibre.com
Subject: Re: [PATCH 5/6] ARM: AM43xx: clk: Change the cpts ref clock source to dpll_core_m5 clk
Date: Mon, 28 Apr 2014 18:25:56 +0530 [thread overview]
Message-ID: <535E4FDC.70306@ti.com> (raw)
In-Reply-To: <20140428071034.GB4380@netboy>
On 4/28/2014 12:40 PM, Richard Cochran wrote:
> On Mon, Apr 28, 2014 at 09:40:24AM +0530, George Cherian wrote:
>> cpsw_cpts_rft_clk has got the choice of 3 clocksources
>> -dpll_core_m4_ck
>> -dpll_core_m5_ck
>> -dpll_disp_m2_ck
>>
>> By default dpll_core_m4_ck is selected, witn this as clock
>> source the CPTS doesnot work properly. It gives clockcheck errors
>> while running PTP.
>>
>> clockcheck: clock jumped backward or running slower than expected!
> It is strange that I have never seen this error, since I have often
> tested linuxptp on a beagle bone white.
In beagle bone white (AM335x) CPTS has a choice of 2 clocksource
-dpll_core_m5_ck
-dpll_core_m4_ck
and by default dpll_core_m5_ck is used. Where as in AM437x the default
clocksource used is dpll_core_m4_ck .
You can change the clocksource in beagle bone white by writing 1 to
0x44e00520 (By default its 0).
>
> Can you please explain why this clock doesn't work correctly?
>
>> By selecting dpll_core_m5_ck as the clocksource fixes this issue.
>> In AM335x dpll_core_m5_ck is the default clocksource.
> The choice of clock source in the CPTS driver originally came from
> TI. It would be nice to know why that was the wrong choice.
>
> Thanks,
> Richard
--
-George
next prev parent reply other threads:[~2014-04-28 12:55 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-28 4:10 [PATCH 0/6] Add CPTS support for AM437x George Cherian
2014-04-28 4:10 ` [PATCH 1/6] drivers: net: cpts: Remove hardcoded clock name for CPTS George Cherian
[not found] ` <1398658225-25873-2-git-send-email-george.cherian-l0cyMroinI0@public.gmane.org>
2014-04-28 6:55 ` Richard Cochran
2014-04-28 14:31 ` Felipe Balbi
2014-04-28 14:45 ` George Cherian
2014-04-28 4:10 ` [PATCH 2/6] ARM: dts: am33xx: Add clock names for cpsw and cpts George Cherian
2014-04-28 4:10 ` [PATCH 3/6] drivers: net: cpsw: Enable CPTS for DRA7xx and AM4372 George Cherian
2014-04-28 4:10 ` [PATCH 4/6] drivers: net: cpsw: Enable Annexe F Time sync George Cherian
[not found] ` <1398658225-25873-5-git-send-email-george.cherian-l0cyMroinI0@public.gmane.org>
2014-04-28 7:55 ` Richard Cochran
2014-04-28 12:58 ` George Cherian
2014-04-28 4:10 ` [PATCH 5/6] ARM: AM43xx: clk: Change the cpts ref clock source to dpll_core_m5 clk George Cherian
2014-04-28 7:10 ` Richard Cochran
2014-04-28 12:55 ` George Cherian [this message]
2014-04-28 16:18 ` Richard Cochran
2014-04-29 4:28 ` George Cherian
[not found] ` <1398658225-25873-1-git-send-email-george.cherian-l0cyMroinI0@public.gmane.org>
2014-04-28 4:10 ` [PATCH 6/6] ARM: dts: am4372: Add clock names for cpsw and cpts George Cherian
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