Re: Problem with DSS clocks & accessing registers

["Cousson, Benoit" <b-cousson@ti.com>]

On 3/7/2011 3:05 PM, Shilimkar, Santosh wrote:
>> From: linux-omap-owner@vger.kernel.org [mailto:linux-omap-
>> owner@vger.kernel.org] On Behalf Of Cousson, Benoit
>>
>> + Rajendra
>>
>> Hi Tomi,
>>
>> On 3/7/2011 9:22 AM, Valkeinen, Tomi wrote:
>>> Hi Kevin, Paul,
>>>
>>> We currently have a small problem with OMAP4 DSS. When we enable
>> the DSS
>>> clocks, it seems that the DSS registers are not always accessible
>> right
>>> after the clock enable.
>>
>> What clocks are you talking about? As you know, the DSS has a bunch
>> of functional clocks available depending of the use case.
>>
>>> I understood that on OMAP4 the clock framework doesn't guarantee
>> that
>>> the registers are accessible after enabling clocks, and pm_runtime
>> will handle this. Is this correct?
>>
>
> This seems to the question about a so called optional clock (DSS_CLK)
> which really not an optional clock :)
> This clock needs to be enabled and disabled along with interface and
> functional clock for the registers access to work.

To be more accurate, this clock is one of the functional clock available 
for the DSS (the other being the SYS_CLK).

You can use dss_clk or sys_clk (through dsi pll) to generate the 
functional clock of the DSS. The issue, as I said is that the 
availability status of the DSS is bound to the DSS module mode, not to 
any of this DSS clock.

Benoit