Re: [PATCH] OMAPDSS: Check if RPM enabled before trying to change state

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On 25 June 2012 15:00, Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote:
> On Mon, 2012-06-25 at 14:19 +0530, Jassi Brar wrote:
>> On 25 June 2012 11:50, Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote:
>> > On Sat, 2012-06-23 at 13:36 +0530, jaswinder.singh@xxxxxxxxxx wrote:
>> ....
>> >>  Currenlty HDMI fails to come up in the suspend-resume path.
>> >> This patch helps that real-world scenario.
>> >
>> > What is the problem there? It'd be good to explain the problem in the
>> > patch description. Does the pm_runtime_get return -EACCES?
>> >
>> Yes, it returns -EACCESS because RPM on devices is disabled during the
>> period from suspend-start to resume-finished.
>
> So... You didn't answer my first comment, how can the code work?
>
Sorry, don't know why I thought I didn't miss anything.

> The driver needs to enable the HW and the call to pm_runtime_get() is
> skipped. Won't this lead to crash as the DSS registers are accessed
> without the HW in enabled state?
>
Hmm...  how does the extant code in hdmi driver ensures DSS is up and running ?
While it does sound important even to my limited knowledge of OMAPDSS,
I see rpm of HDMI, VENC and RFBI only dependent on DISPC, not DSS.

And for DISPC these drivers already hold a reference in their display
enable/resume and keep it until disable/suspend. So we don't lose
DISPC anytime it is really required.

> And what happens if the pm_runtime_get() call is skipped, but pm_runtime_put() is not?
>
Not sure in what newly introduced scenario by this patch, because
get/put both check for pm_enabled before proceeding. Am I overlooking
something?

thnx
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