On Tue, Jul 13, 2010 at 01:00:51PM +0200, Linus Walleij wrote:

In the U300 (maybe the U8500 as well, I don't know OTOH) the
APB pclk and e.g. SSPCLK is simply just wired together and
connected to the same clock terminal. This means that currently
the PCLK is toggled on/off in unison with the SSPCLK all the time
already, and it's working.

That means you want to alias the device specific apb_pclk to the same
struct clk as (eg) the device's sspclk - which means that when the
driver wants either PCLK or SSPCLK to be on, the bit to enable them
will be turned on.

Since that works, it means that we can likely insert
amba_bus_clk_[disable|enable] at the same sites that we have
this in the current code for the external clocks at the same time,
atleast for pl011, pl022 and pl180.

Almost - but there's a few corner cases.  Basically, what I think you'll
need for pl011 is:
1. add an amba_bus_clk_disable() at the end of the successful probe
   function
2. add amba_bus_clk_enable() at the beginning of the remove function.
3. add amba_bus_clk_enable()/amba_bus_clk_disable() around each of the
   suspend(), resume(), pl011_console_write(), and
   pl011_console_get_options() functions.
4. amba_bus_clk_enable() at the start of the startup method.
5. amba_bus_clk_disable() at the end of the shutdown method.

Most of these do tie up with existing clk_enable()s, but there are some
additional places you'd need to enable the pclk because of register
accesses.