linux-kernel - Re: [RESEND PATCH v6 2/4] media: chips-media: wave5: Support runtime suspend/resume

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Date: Thu, 20 Jun 2024 10:03:15 -0400
From: Nicolas Dufresne <nicolas.dufresne@...labora.com>
To: "jackson.lee" <jackson.lee@...psnmedia.com>, Devarsh Thakkar
	 <devarsht@...com>, "mchehab@...nel.org" <mchehab@...nel.org>, 
 "sebastian.fricke@...labora.com"
	 <sebastian.fricke@...labora.com>
Cc: "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>, 
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "hverkuil@...all.nl" <hverkuil@...all.nl>,  Nas Chung
 <nas.chung@...psnmedia.com>, "lafley.kim" <lafley.kim@...psnmedia.com>,
 "b-brnich@...com" <b-brnich@...com>
Subject: Re: [RESEND PATCH v6 2/4] media: chips-media: wave5: Support
 runtime suspend/resume

Hi Jackson, Devarsh,

Le mercredi 19 juin 2024 à 23:56 +0000, jackson.lee a écrit :
> Hi Devarsh
> 
> If there is no feeding bitstreams during encoding and decoding frames, then driver's status is switched to suspended automatically by autosuspend.
> And if we don’t use autosuspend, it is very difficult for us to catch if there is feeding or not while working a pipeline.
> So it is very efficient for managing power status.
> 
> If the delay is very great value, we can adjust it.

One way to resolve this, would be if someone share measurement of the suspend /
resume cycle duration. With firmware (third party OS) like this, the cost and
duration is few order of magnitude higher then with more basic ASIC like Hantro
and other single function HW.

Yet, 5s might be to much (but clearly safe), but getting two low may means that
we suspect "between two frames", and if that happens, we may endup with various
range of side effect, like reduce throughput due to suspend collisions, or even
worse power footprint. Some lab testing to adjust the value will be needed, we
have very little of that happening at the moment as I understood.

Nicolas

> 
> Thanks
> Jackson
> 
> > -----Original Message-----
> > From: Devarsh Thakkar <devarsht@...com>
> > Sent: Wednesday, June 19, 2024 10:00 PM
> > To: jackson.lee <jackson.lee@...psnmedia.com>; mchehab@...nel.org;
> > nicolas@...fresne.ca; sebastian.fricke@...labora.com
> > Cc: linux-media@...r.kernel.org; linux-kernel@...r.kernel.org;
> > hverkuil@...all.nl; Nas Chung <nas.chung@...psnmedia.com>; lafley.kim
> > <lafley.kim@...psnmedia.com>; b-brnich@...com; Nicolas Dufresne
> > <nicolas.dufresne@...labora.com>
> > Subject: Re: [RESEND PATCH v6 2/4] media: chips-media: wave5: Support runtime
> > suspend/resume
> > 
> > Hi Jackson,
> > 
> > Thanks for the patch.
> > On 17/06/24 16:18, Jackson.lee wrote:
> > > From: "jackson.lee" <jackson.lee@...psnmedia.com>
> > > 
> > > Add support for runtime suspend/resume in the encoder and decoder.
> > > This is achieved by saving the VPU state and powering it off while the VPU
> > idle.
> > > 
> > > Signed-off-by: Jackson.lee <jackson.lee@...psnmedia.com>
> > > Signed-off-by: Nas Chung <nas.chung@...psnmedia.com>
> > > Reviewed-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
> > 
> > [..]
> > >  static int wave5_vpu_probe(struct platform_device *pdev)  {
> > >  	int ret;
> > > @@ -268,6 +301,12 @@ static int wave5_vpu_probe(struct platform_device
> > *pdev)
> > >  		 (match_data->flags & WAVE5_IS_DEC) ? "'DECODE'" : "");
> > >  	dev_info(&pdev->dev, "Product Code:      0x%x\n", dev->product_code);
> > >  	dev_info(&pdev->dev, "Firmware Revision: %u\n", fw_revision);
> > > +
> > > +	pm_runtime_set_autosuspend_delay(&pdev->dev, 5000);
> > 
> > Why are we putting 5s delay for autosuspend ? Without using auto-suspend
> > delay too, we can directly go to suspended state when last instance is closed
> > and resume back when first instance is open.
> > 
> > I don't think having an autosuspend delay (especially of 5s) bodes well with
> > low power-centric devices such as AM62A where we would prefer to go to
> > suspend state as soon as possible when the last instance is closed.
> > 
> > Also apologies for the delay in review, this didn't caught my eye earlier as
> > commit message did not mention it either.
> > 
> > Regards
> > Devarsh