linux-kernel - Re: [PATCH v2 12/23] media: rkvdec: Stop overclocking the decoder

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Date:   Sat, 2 Apr 2022 08:05:46 -0300
From:   Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:     Nicolas Dufresne <nicolas.dufresne@...labora.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kernel@...labora.com,
        Sebastian Fricke <sebastian.fricke@...labora.com>,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 12/23] media: rkvdec: Stop overclocking the decoder

On Thu, Mar 31, 2022 at 03:37:14PM -0400, Nicolas Dufresne wrote:
> While this overclock hack seems to work on some implementations
> (some ChromeBooks, RockPi4) it also causes instability on other
> implementations (notably LibreComputer Renegade, but there were more
> reports in the LibreELEC project, where this has been removed). While
> performance is indeed affected (tested with GStreamer), 4K playback
> still works as long as you don't operate in lock step and keep at
> least 1 frame ahead of time in the decode queue.
> 
> After discussion with ChromeOS members, it would seem that their
> implementation indeed used to synchronously decode each frames, so
> this hack was simply compensating for their code being less
> efficient. In my opinion, this hack should not have been included
> upstream.
> 
> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
> Reviewed-by: Sebastian Fricke <sebastian.fricke@...labora.com>

Fixes: cd33c830448ba ("media: rkvdec: Add the rkvdec driver")
Reviewed-by: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>

Thanks,
Ezequiel

> ---
>  drivers/staging/media/rkvdec/rkvdec.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/drivers/staging/media/rkvdec/rkvdec.c b/drivers/staging/media/rkvdec/rkvdec.c
> index c0cf3488f970..2df8cf4883e2 100644
> --- a/drivers/staging/media/rkvdec/rkvdec.c
> +++ b/drivers/staging/media/rkvdec/rkvdec.c
> @@ -1027,12 +1027,6 @@ static int rkvdec_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> -	/*
> -	 * Bump ACLK to max. possible freq. (500 MHz) to improve performance
> -	 * When 4k video playback.
> -	 */
> -	clk_set_rate(rkvdec->clocks[0].clk, 500 * 1000 * 1000);
> -
>  	rkvdec->regs = devm_platform_ioremap_resource(pdev, 0);
>  	if (IS_ERR(rkvdec->regs))
>  		return PTR_ERR(rkvdec->regs);
> -- 
> 2.34.1
>