linux-kernel - RE: [PATCH v3 03/10] ARM: OMAP: AM33xx hwmod: Add parent-child relationship for PWM subsystem

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Date:	Tue, 27 Nov 2012 06:24:03 +0000
From:	"Philip, Avinash" <avinashphilip@...com>
To:	"Bedia, Vaibhav" <vaibhav.bedia@...com>,
	"Cousson, Benoit" <b-cousson@...com>
CC:	"thierry.reding@...onic-design.de" <thierry.reding@...onic-design.de>,
	"paul@...an.com" <paul@...an.com>,
	"tony@...mide.com" <tony@...mide.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"Hiremath, Vaibhav" <hvaibhav@...com>,
	"AnilKumar, Chimata" <anilkumar@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"Nori, Sekhar" <nsekhar@...com>,
	"Hebbar, Gururaja" <gururaja.hebbar@...com>
Subject: RE: [PATCH v3 03/10] ARM: OMAP: AM33xx hwmod: Add parent-child
 relationship for PWM subsystem

On Mon, Nov 26, 2012 at 16:37:36, Bedia, Vaibhav wrote:
> Hi Benoit,
> 
> On Mon, Nov 26, 2012 at 14:32:59, Cousson, Benoit wrote:
> > Hi Vaibhav,
> > 
> > On 11/26/2012 06:19 AM, Bedia, Vaibhav wrote:
> > > On Fri, Nov 23, 2012 at 16:36:06, Philip, Avinash wrote:
> > >> On Tue, Nov 20, 2012 at 10:33:44, Philip, Avinash wrote:
> > >>> As part of PWM subsystem integration, PWM subsystem are sharing
> > >>> resources like clock across submodules (ECAP, EQEP & EHRPWM).
> > >>> To handle resource sharing & IP integration
> > >>> 1. Rework on parent child relation between PWMSS and
> > >>>    ECAP, EQEP & EHRPWM child devices to support runtime PM.
> > >>> 2. Add support for opt_clks in EHRPWM HWMOD entry to handle additional
> > >>>    clock gating from control module.
> > >>> 3. Add HWMOD entries for EQEP PWM submodule.
> > >>>
> > >>
> > >> Is there any review on this patch?
> > >> This patch depends on ECAP & EHRPWM to work in am335x.
> > > 
> > > First of all, I think you should break up this patch as per the 3 points
> > > that you mentioned above.

I will split the patches into 2.
1. One for correcting hwmod entries  plus adding EQEP HWMOD entry
2. Adding parent child relation in hwmod entry.

> > > 
> > > The usage of opt_clks for this does not look right to me. Based on your
> > > description this clock is necessary and not optional on AM335x and on 
> > > Davinci platforms this clock does not exist.
> 
> I checked the DA830 TRM and looks like TBCLK for eHRPWM is an always on clock
> there. So, the only difference in AM335x is an additional enable bit.
> 
> Instead of adding this as opt_clk in hwmod, we could add an always on clock node
> in Davinci clock data and have the driver always do a clk_enable() on the tbclk
> as part of the probe sequence. On AM335x, with the right clock node this will enable
> the clock in hardware and on DA830 it turns into a NOP. This way we can avoid adding
> the opt_clk entry in hwmod of eHRPWM.

I will remove opt_clk in HWMOD and made tbclk is a mandatory clock in EHRPWM driver.

Thanks
Avinash
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