[PATCH 09/19] drivers: serial: add support for Samsung S5PC110 SoC uart

[jassi brar]

On Thu, Nov 19, 2009 at 8:48 PM, Mark Brown
<broonie at opensource.wolfsonmicro.com> wrote:
> On Thu, Nov 19, 2009 at 11:38:41AM +0000, Russell King - ARM Linux wrote:
>
>> I'm not sure what you're commenting on precisely, but the Samsung code as
>> a whole doesn't use the clk API very well, and I suspect that is starting
>> to cause people to have to pass clock names around.
>
> That's what I'd thought originally but it's not quite the problem here.
> The issue is that Samsung serial port clock is chosen from a mux and the
> logic to select which of the inputs to that mux should be used is in the
> serial driver.  This means that if the set of parent clocks changes then
> the serial driver needs to be told what they are.
just to add to the info: unlike system clocks and mux'es which are controlled
by registers of a dedicated clock/system controller, this uart mux is
managed by bits of some register of the UART controller.

> My suggestion was to push this logic down into the clock API so the
> serial driver just requests a rate and then clock API picks the best
> option from the mux.  As well as being nicer from the clock API point of
> view this would also allow other drivers to use the same logic since
> these muxes are a standard idiom for Samsung SoCs.
how transparently could we add this 'uart-mux' into the clock API, provided
that the register space ioremap'ing is done in the uart driver, is to be seen.