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

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Message-ID: <CAAe_U6+JpyLrK9v3uae+yN1zCigMQc=JaEMAOZgupurCzuWDcA@mail.gmail.com>
Date:	Wed, 12 Sep 2012 12:06:16 +0530
From:	"ABRAHAM, KISHON VIJAY" <kishon@...com>
To:	Paul Walmsley <paul@...an.com>
Cc:	b-cousson@...com, 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,

On Wed, Sep 12, 2012 at 3:58 AM, Paul Walmsley <paul@...an.com> wrote:
> 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

It should be added in omap-usb2 driver rather.
> 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_*() ?

We have omap-usb2 driver that is used for both omap4 and omap5. But
this 48m clock is used only in omap4. And we dint have any *main_clk*
in the ocp2scp_usb_phy_hwmod. So in order avoid some checks in the
omap-usb2 driver, we added 48m clk as the main clock of
ocp2scp_usb_phy_hwmod.

Thanks
Kishon
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