linux-kernel - Re: [PATCH v2] arm: omap: hwmod: make *phy_48m* as the main

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Date:	Tue, 11 Sep 2012 22:28:22 +0000 (UTC)
From:	Paul Walmsley <paul@...an.com>
To:	Kishon Vijay Abraham I <kishon@...com>, b-cousson@...com
cc:	balbi@...com, tony@...mide.com, linux@....linux.org.uk,
	arnd@...db.de, gregkh@...uxfoundation.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm: omap: hwmod: make *phy_48m* as the main_clk of
 ocp2scp

Hi Kishon, Benoît,

On Fri, 7 Sep 2012, Kishon Vijay Abraham I wrote:

> Made *ocp2scp_usb_phy_phy_48m* as the main_clk for ocp2scp. Since this 
> ocp2scp module does not have any fck but does have a single opt_clock, 
> it is added as the main_clk for ocp2scp. Also removed phy_48m as the 
> optional clock since it is now made as the main clock. By this the 
> driver need not enable/disable phy_48m clk separately and 
> runtime_get/runtime_put will take care of that.

Looking at this patch, it doesn't seem to make sense from a hardware point 
of view.  If you look at the OMAP4430 TRM Rev. AE, Table 23-1166 "Clocks 
and Resets", the 48MHz clock input is listed as an "Optional functional 
clock".  The main functional clock is listed as "INIT_960M_FCLK", which 
according to the same TRM, Section 3.6.3.9.1 "Overview", is an alias for 
the clock we call "dpll_usb_clkdcoldo_ck".

So if any clock should be the main functional clock in the hwmod data, 
shouldn't it be dpll_usb_clkdcoldo_ck?  The goal with the hwmod data 
is/was to have it match the hardware.

...

More to the point, I guess I don't see what the problem is with 
adding a few lines to the ocp2scp driver to control the "phy_48m" optional 
clock via the clock framework.  Is there some reason why you 
couldn't prepare & enable it after the pm_runtime_get_*(), 
and disable and unprepare it before the pm_runtime_put_*() ?

- Paul