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 18:30:07 +0530
From: Devarsh Thakkar <devarsht@...com>
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@...psnmedia.com>,
        <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