Re: [PATCH 3/5] [media]: OMAP_VOUT: Fix VSYNC IRQ handling in omap_vout_isr

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Hi Vaibhav,
>>
>> On Mon, Sep 26, 2011 at 3:49 PM, Hiremath, Vaibhav <hvaibhav@xxxxxx> wrote:
>>>
>>> > -----Original Message-----
>>> > From: Taneja, Archit
>>> > Sent: Thursday, September 22, 2011 11:46 AM
>>> > To: Hiremath, Vaibhav
>>> > Cc: Valkeinen, Tomi; linux-omap@xxxxxxxxxxxxxxx; Semwal, Sumit; linux-
>>> > media@xxxxxxxxxxxxxxx
>>> > Subject: Re: [PATCH 3/5] [media]: OMAP_VOUT: Fix VSYNC IRQ handling in
>>> > omap_vout_isr
>>> >
>>> > Hi,
>
>   <snip>
>>>
>>> > >> -          if (!(irqstatus&  (DISPC_IRQ_VSYNC | DISPC_IRQ_VSYNC2)))
>>> > >> +          if (mgr_id == OMAP_DSS_CHANNEL_LCD)
>>> > >> +                  irq = DISPC_IRQ_VSYNC;
>>> > >> +          else if (mgr_id == OMAP_DSS_CHANNEL_LCD2)
>>> > >> +                  irq = DISPC_IRQ_VSYNC2;
>>> > >> +          else
>>> > >> +                  goto vout_isr_err;
>>> > >> +
>>> > >> +          if (!(irqstatus&  irq))
>>> > >>                    goto vout_isr_err;
>>> > >>            break;
>>> > > I understand what this patch meant for, but I am more curious to know
>>> > > What is value addition of this patch?
>>> > >
>>> > > if (!(irqstatus&  (DISPC_IRQ_VSYNC | DISPC_IRQ_VSYNC2)))
>>> > >
>>> > > Vs
>>> > >
>>> > > if (mgr_id == OMAP_DSS_CHANNEL_LCD)
>>> > >     irq = DISPC_IRQ_VSYNC;
>>> > > else if (mgr_id == OMAP_DSS_CHANNEL_LCD2)
>>> > >     irq = DISPC_IRQ_VSYNC2;
>>> > >
>>> > > Isn't this same, because we are not doing anything separate and special
>>> > > for VSYNC and VSYNC2?
>>> >
>>> > Consider a use case where the primary LCD panel(connected to LCD
>>> > manager) is configured at a 60 Hz refresh rate, and the secondary
>>> > panel(connected to LCD2) refreshes at 30 Hz. Let the overlay
>>> > configuration be something like this:
>>> >
>>> > /dev/video1----->overlay1----->LCD manager----->Primary panel(60 Hz)
>>> >
>>> >
>>> > /dev/video2----->overlay2----->LCD2 manager----->Secondary Panel(30 Hz)
>>> >
>>> >
>>> > Now if we are doing streaming on both video1 and video2, since we deque
>>> > on either VSYNC or VSYNC2, video2 buffers will deque faster than the
>>> > panels refresh, which is incorrect. So for video2, we should only deque
>>> > when we get a VSYNC2 interrupt. Thats why there is a need to correlate
>>> > the interrupt and the overlay manager.
>>> >
>>>
>>> Archit,
>>>
>>> I think I am still not understood or convinced with your description above,
>>>
>>> The code snippet which we are referring here, does check whether the
>>> interrupt is either VSYNC or VSYNC2, else fall back to "vout_isr_err".
>
>
I am not quite sure I understand what is the confusing part here -
below is my understanding; please correct me if you think otherwise.
As I understand, this patch creates a (missing) correlation between a
manager and the corresponding ISR. The earlier code would accept a
VSYNC2 for LCD1 manager, which is not the correct thing to do.
That is why the check of 'if ((mgr==LCD) && (IRQ==VSYNC))' kind of
thing is needed; Which part of this do you think the above patch
doesn't do? Or, do you think it is not needed / done correctly?
>>>
>>> For me both are doing same thing, the original code is optimized way of implementation. Can you please review it again?
>>>
>>> Thanks,
>>> Vaibhav
>
>
Thanks and best regards,
~Sumit.
>>>
>>> <snip>
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