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

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Date: Wed, 19 Jun 2024 23:56:51 +0000
From: jackson.lee <jackson.lee@...psnmedia.com>
To: Devarsh Thakkar <devarsht@...com>, "mchehab@...nel.org"
	<mchehab@...nel.org>, "nicolas@...fresne.ca" <nicolas@...fresne.ca>,
	"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>, Nicolas Dufresne
	<nicolas.dufresne@...labora.com>
Subject: RE: [RESEND PATCH v6 2/4] media: chips-media: wave5: Support runtime
 suspend/resume

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.

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