Re: [PATCH 1/2] clk: tegra: remove USB from clk init table

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 01/28/2013 11:45 AM, Lucas Stach wrote:
> Am Montag, den 28.01.2013, 11:37 -0700 schrieb Stephen Warren:
>> On 01/27/2013 03:17 PM, Lucas Stach wrote:
>>> The USB clocks are just clock gates, so no need to set a specific clock.
>>> In fact trying to set a specific clock is just a NOP if the requested
>>> clockrate is the same as those of the parent (clk_m) or will trigger a
>>> WARN_ON() if rates don't match up.
>>>
>>> As we are not setting a specific rate, nor activating the clocks at
>>> init, there is no point in keeping the the usb entries in the clock init
>>> table.
>>
>> I'm not convinced here; aren't the USB clocks supposed to be driven by
>> PLL U?
>>
>> Prashant, Peter, Venu, can you please comment here.
>
> I was a bit confused at first, too. But what I am removing here is the
> clockgate init for the USB controllers. The clocks driven by PLL_U are
> the USB PHY clocks, which are a separate set of clocks.

I don't think these are always separate.

If you look at the USB driver drivers/usb/phy/tegra_usb_phy.c, you'll
see that for UTMI there's a clk_get_sys("utmip-pad"), which per
drivers/clk/tegra/clk-tegra20.c is an alias for clock "usbd" which is
the USB1 controller clock (it's also aliased to "tegra-ehci.0").
However, for ULPI, there's a clk_get_sys(ulpi_config->clk), which is
"cdev2", which is separate from any USB controller clock.