OMAP3 DSP MMU fault + off mode issue

[venki kaps]

Venkii,
On Wed, Sep 15, 2010 at 9:12 PM, venki kaps <venkiece2005 at gmail.com> wrote:
> Venkii,
> On Wed, Sep 15, 2010 at 8:02 PM, Kevin Hilman
> <khilman at deeprootsystems.com> wrote:
>> venki kaps <venkiece2005 at gmail.com> writes:
>>
>>> On Tue, Sep 14, 2010 at 8:54 PM, venki kaps <venkiece2005 at gmail.com> wrote:
>>>> On Tue, Sep 14, 2010 at 1:28 AM, venki kaps <venkiece2005 at gmail.com> wrote:
>>>>> Dear all,
>>>>>
>>>>> I have been facing an issue with OMAP3 PM with DSP MMU Fault (Kernel 2.6.32).
>>>>>
>>>>> The issue is describing as below mentioned way,
>>>>>        1). The Device is getting DSP MMU Fault when playing MP4 video clip.
>>>>>
>>>>> The system is not hitting off mode in the below scenario,
>>>>>        2). System boot ->play mp4 clip ->DSP MMU Fault -> allow off
>>>>> mode -----------> Never hits off mode
>>>>>
>>>>> But surprisingly the system is hitting off mode in the below scenario,
>>>>>       3). System boot ->allow off mode ->play mp4 clip ->DSP MMU
>>>>> Fault -> allow off mode -----------> perfectly works
>>>>>
>>>>>
>>>>>  - Could you please describe the root cause about the above issues 1 & 2?
>>>>>  - How could solve the above issues?
>>>>
>>>> I have found the issue with UART3.
>>>> In System configuration register (SYSC),-
>>>>             IDLEMODE  - Smart idle -------> working scenario  ------>
>>>> system hits off mode.
>>>>             IDLEMODE  - No idle -------> Non working scenario
>>>> ------> system never hits off mode.
>>>>
>>>> Could you please explain why UART3 is not able to hit smart idle after
>>>> DSP MMU fault ( System boot ->play mp4 clip ->DSP MMU Fault -> allow
>>>> off -----------> Never hits off mode).,
>>>
>>> My problem is resolved.GPtimer7 was not reset during the MMU FAULT
>>> occurrence before the first power cycle.
>>> So this pending interrupt is preventing the system sleep entry.
>>> Now it works fine after resetting Gptimer7 in pm suspend path.
>>
>> Sounds like a patch is needed for DSPBridge who manages that timer.
>
> Patchwork DSPBRIDGE: MMU-Fault debugging enhancements,
> https://patchwork.kernel.org/patch/91577/
> From the above patch, please see the below comment
> /*
>  * Send a GP Timer interrupt to DSP
>  * The DSP expects a GP timer interrupt after an
>  * MMU-Fault Request GPTimer
>  */
>
> The above changes allow for DSP task information to be printed
> by the MPU dspbridge when DSP MMU fault ocurrs.
>
> This above changes will be required during development.
> In my scenario, it is not required so i have just commented.
>
> Index: android-2.6.32.9/drivers/dsp/bridge/wmd/ue_deh.c
> ===================================================================
> --- android-2.6.32.9.orig/drivers/dsp/bridge/wmd/ue_deh.c
> 2010-08-24 18:19:19.000000000 +0900
> +++ android-2.6.32.9/drivers/dsp/bridge/wmd/ue_deh.c    2010-09-16
> 00:28:52.000000000 +0900
> @@ -285,7 +285,8 @@
>                         * The DSP expects a GP timer interrupt after an
>                         * MMU-Fault Request GPTimer
>                         */
> -                       if (timer) {
> +                       if (0) {
>                                omap_dm_timer_enable(timer);
>                                /* Enable overflow interrupt */
>                                omap_dm_timer_set_int_enable(timer,
>

In latest kernels (Eg, linux-2.6.36-rc3),The MMU-Fault debugging
enhancements code is moved under CONFIG_TIDSPBRIDGE_BACKTRACE.

>> Kevin
>>
>