linux-kernel - Re: [PATCH 2/5] ARM: OMAP2+: DRA7: Add hwmod entries for PWMSS

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Date:	Tue, 2 Jun 2015 16:54:10 +0530
From:	Vignesh R <vigneshr@...com>
To:	Tero Kristo <t-kristo@...com>, Paul Walmsley <paul@...an.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Benoit Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>
CC:	<linux-pwm@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-clk@...r.kernel.org>
Subject: Re: [PATCH 2/5] ARM: OMAP2+: DRA7: Add hwmod entries for PWMSS

Hi Tero,

On Tuesday 02 June 2015 01:51 PM, Tero Kristo wrote:
> On 06/01/2015 02:53 PM, Vignesh R wrote:
>> Add hwmod entries for the PWMSS on DRA7.
> 
> Can you provide some documentation references for this data?
> 
> I was looking at the TRM and at least the main_clk selection is somewhat
> unclear to me.

As per AM57x TRM SPRUHZ6, October 2014, Section 29.1.3 Table 29-4.
source signal as L4PER2_L3_GICLK but it is actually equal to
L4PER2_L3_GICLK/2. l4_root_clock_div is fixed-factored clock equal to
L4PER2_L3_GICLK/2 (l3_iclk_div/2 in Linux clock dt). The TRM does'nt
show factor of by 2. I will forward you an internal documentation that
talks about this.

I also measured the frequencies of PWM waveforms using oscilloscope and
it matches above observation.

I will update the patch description in v2.

Regards
Vignesh

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