Re: [PATCH v5 02/14] ARM: OMAP2+: gpmc: Adapt to HWMOD

[Jon Hunter <jon-hunter@ti.com>]

Hi Afzal,

On 06/13/2012 12:20 AM, Mohammed, Afzal wrote:
> Hi Jon,
> 
> On Tue, Jun 12, 2012 at 23:10:01, Hunter, Jon wrote:
>> On 06/12/2012 01:53 AM, Mohammed, Afzal wrote:
>>> On Tue, Jun 12, 2012 at 01:26:29, Hunter, Jon wrote:
> 
>>>> My preference would be to store gpmc_l3_clk in the pdata and pass to
>>>> probe via the pdata. The aim would be to remove the global gpmc_l3_clk
>>>> altogether.
>>>
>>> For timing calculation by platform outside of driver, we need clk rate
>>
>> Right but potentially, this could be done by the driver.
> 
> I do not think it is practically possible. Please see timing calculations
> in arch/arm/mach-omap2/gpmc-*, the way it is done for different
> peripherals are different, and we cannot expect gpmc driver to do those as
> that would require gpmc driver being aware of type of peripheral connected.
> 
> And all those gpmc-* timing calculation needs to be done before driver
> is ready, they rely on functions like gpmc_get_fclk_rate(), which in turn
> requires the clk rate to be available before driver is probed.

So I see that the various gpmc-*.c files have some form of _retime()
function. However, at the end of the day they all call
gpmc_cs_set_timings() to convert time into gpmc clocks. Converting time
to gpmc clocks is completely independent of the actual device and so
this can be performed by the driver. We just need to populate the
gpmc_timings struct and pass to the driver to convert to clocks and
program into the registers.

If the clk handle for the gpmc is passed to the gpmc driver, then there
is no reason why the driver cannot do this.

Obviously, I could be missing something fundamental here, but my
assumption is that if the driver has the handle the fclk (and hence can
query the clock rate) and has then gpmc_timings struct (with timings in
time), then that is all it needs.

Cheers
Jon