linux-kernel - RE: [PATCH v2 2/7] media: chips-media: wave5: Improve performance of decoder

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Message-ID:
 <SE1P216MB1303BED1AD4E7C782BA14E66ED6BA@SE1P216MB1303.KORP216.PROD.OUTLOOK.COM>
Date: Mon, 9 Jun 2025 08:47:53 +0000
From: jackson.lee <jackson.lee@...psnmedia.com>
To: Nicolas Dufresne <nicolas.dufresne@...labora.com>, "mchehab@...nel.org"
	<mchehab@...nel.org>, "hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>,
	"bob.beckett@...labora.com" <bob.beckett@...labora.com>
CC: "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, lafley.kim
	<lafley.kim@...psnmedia.com>, "b-brnich@...com" <b-brnich@...com>,
	"hverkuil@...all.nl" <hverkuil@...all.nl>, Nas Chung
	<nas.chung@...psnmedia.com>
Subject: RE: [PATCH v2 2/7] media: chips-media: wave5: Improve performance of
 decoder

Hi Nicolas

I will find the way to reduce overhead after receiving the STOP_CMD.

thanks

> -----Original Message-----
> From: Nicolas Dufresne <nicolas.dufresne@...labora.com>
> Sent: Thursday, June 5, 2025 10:29 PM
> To: jackson.lee <jackson.lee@...psnmedia.com>; mchehab@...nel.org;
> hverkuil-cisco@...all.nl; bob.beckett@...labora.com
> Cc: linux-media@...r.kernel.org; linux-kernel@...r.kernel.org; lafley.kim
> <lafley.kim@...psnmedia.com>; b-brnich@...com; hverkuil@...all.nl; Nas
> Chung <nas.chung@...psnmedia.com>
> Subject: Re: [PATCH v2 2/7] media: chips-media: wave5: Improve performance
> of decoder
> 
> Hi,
> 
> Le jeudi 05 juin 2025 à 04:50 +0000, jackson.lee a écrit :
> > > So my question is, is there a way to know, at CMD_STOP call, that
> > > the HW has gone idle, and that no more events will allow handling the
> EOS case?
> > >
> > > Nicolas
> >
> >
> > Thanks for your reply.
> >
> > Now there is only one thing to know if there is more events or not to
> handle the EOS case.
> > It is that driver sends DEC_PIC command to VPU continuously until
> display index is -2(it means EOS) from VPU.
> > VPU should trigger interrupts to get display index from the
> finish_decode function.
> > So we have to run device_run to send DEC_PIC command.
> 
> What don't want to see is a loop where we do:
> 
> 	device_run()
> 		finish_job()
> 			device_run()
> 				finish_job()
> 					....
> 
> What I see now, is that we simply bang on the trigger until it completes,
> which is very wasteful in power and CPU time. In your next version, make
> sure to find a mitigation to that active loop, and document it please.
> 
> Nicolas