linux-kernel - Re: [PATCH 2/2] ARM: omap5/dra7xx: Fix counter frequency drift for AM572x errata i856.

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Date:	Wed, 17 Dec 2014 17:56:40 +0200
From:	Tero Kristo <t-kristo@...com>
To:	Nishanth Menon <nm@...com>
CC:	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>,
	Lokesh Vutla <lokeshvutla@...com>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Sekhar Nori <nsekhar@...com>
Subject: Re: [PATCH 2/2] ARM: omap5/dra7xx: Fix counter frequency drift for
 AM572x errata i856.

On 12/17/2014 05:53 PM, Nishanth Menon wrote:
> On 17:45-20141217, Tero Kristo wrote:
>> On 12/17/2014 05:27 PM, Lennart Sorensen wrote:
>>> On Wed, Dec 17, 2014 at 09:22:25AM -0600, Nishanth Menon wrote:
>>>> A clock mux might do the job?
>>>>
>>>> value 1, 2 , 3 will imply sysclk1 / 610
>>>> value of 0 implies fixed 32768
>>>>
>>>> soemthing like
>>>> sys_clk32_crystal {
>>>>                 compatible = "fixed-clock";
>>>>                 clock-frequency = <32768>;
>>>> }
>>>>
>>>> sys_clk32_pseudo {
>>>>                 compatible = "fixed-clock";
>>>>                 compatible = "fixed-factor-clock";
>>>>                 clocks = <&sys_clkin1>;
>>>>                 clock-mult = <1>;
>>>>                 clock-div = <610>;
>>>> }
>>>>
>>>> sys_32k_ck: sys_32k_ck {
>>>> 	compatible = "ti,mux-clock";
>>>> 	clocks = <&sys_clk32_crystal>, <&sys_clk32_pseudo>, <&sys_clk32_pseudo>, <&sys_clk32_pseudo>;
>>>> };
>>>>
>>>> I think... The only issue is that the BOOTSTRAP register is not around
>>>> the usual CM1,2 address region...
>>>
>>> OK, I like where that idea is headed.  That looks promising.
>>>
>>
>> Yea clock mux can be used. However, we don't have support for DRA7
>> control module clocks in the DT yet. I have posted patches with
>> support towards this a couple of weeks back, but they need some
>> revising.
>>
>> Thus, we maybe need to apply the timer patches as is for now, and
>> fix the clock tree a bit later.
>
> Sounds good to me, could you propose a patch in list?

Yea, I can add a patch for this to the PRCM cleanup set once I get to 
update that.

-Tero

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