Re: [PATCH v1 4/5] media: rkvdec: Re-enable H.264 error detection

From: Alex Bee <knaerzche@gmail.com>
To: Nicolas Dufresne <nicolas.dufresne@collabora.com>,
	linux-media@vger.kernel.org,
	Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: kernel@collabora.com, linux-rockchip@lists.infradead.org,
	linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 4/5] media: rkvdec: Re-enable H.264 error detection
Date: Sat, 11 Jun 2022 14:08:05 +0200	[thread overview]
Message-ID: <8efa6811-ee17-4dd2-23a7-e0471af8c0a6@gmail.com> (raw)
In-Reply-To: <20220610125215.240539-5-nicolas.dufresne@collabora.com>

Am 10.06.22 um 14:52 schrieb Nicolas Dufresne:
> This re-enables H.264 error detection, but using the other error mode.
> In that mode, the decoder will skip over the error macro-block or
> slices and complete the decoding. As a side effect, the error status
> is not set in the interrupt status register, and instead errors are
> detected per format. Using this mode workaround the issue that the
> HW get stuck in error stated and allow reporting that some corruption
> may be present in the buffer returned to userland.
> 
> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
> ---
>  drivers/staging/media/rkvdec/rkvdec-h264.c | 23 +++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/media/rkvdec/rkvdec-h264.c b/drivers/staging/media/rkvdec/rkvdec-h264.c
> index 55596ce6bb6e..60a89918e2c1 100644
> --- a/drivers/staging/media/rkvdec/rkvdec-h264.c
> +++ b/drivers/staging/media/rkvdec/rkvdec-h264.c
> @@ -1175,14 +1175,15 @@ static int rkvdec_h264_run(struct rkvdec_ctx *ctx)
>  
>  	schedule_delayed_work(&rkvdec->watchdog_work, msecs_to_jiffies(2000));
>  
> -	writel(0, rkvdec->regs + RKVDEC_REG_STRMD_ERR_EN);
> -	writel(0, rkvdec->regs + RKVDEC_REG_H264_ERR_E);
> +	writel(0xffffffff, rkvdec->regs + RKVDEC_REG_STRMD_ERR_EN);
> +	writel(0xffffffff, rkvdec->regs + RKVDEC_REG_H264_ERR_E);
>  	writel(1, rkvdec->regs + RKVDEC_REG_PREF_LUMA_CACHE_COMMAND);
>  	writel(1, rkvdec->regs + RKVDEC_REG_PREF_CHR_CACHE_COMMAND);
>  
>  	/* Start decoding! */
>  	writel(RKVDEC_INTERRUPT_DEC_E | RKVDEC_CONFIG_DEC_CLK_GATE_E |
> -	       RKVDEC_TIMEOUT_E | RKVDEC_BUF_EMPTY_E,
> +	       RKVDEC_TIMEOUT_E | RKVDEC_BUF_EMPTY_E |
> +	       RKVDEC_H264ORVP9_ERR_MODE,
>  	       rkvdec->regs + RKVDEC_REG_INTERRUPT);
>  
>  	return 0;
> @@ -1196,10 +1197,26 @@ static int rkvdec_h264_try_ctrl(struct rkvdec_ctx *ctx, struct v4l2_ctrl *ctrl)
>  	return 0;
>  }
>  
> +static int rkvdec_h264_check_error_info(struct rkvdec_ctx *ctx)
> +{
> +	struct rkvdec_dev *rkvdec = ctx->dev;
> +	int err;
> +
> +	err = readl(rkvdec->regs + RKVDEC_REG_H264_ERRINFO_NUM);
> +	if (err & RKVDEC_STRMD_DECT_ERR_FLAG) {
> +		pr_debug("Decoded picture have %i/%i slices with errors.\n",
> +			 RKVDEC_ERR_PKT_NUM(err), RKVDEC_SLICEDEC_NUM(err));
> +		return VB2_BUF_STATE_ERROR;
> +	}
> +
> +	return VB2_BUF_STATE_DONE;
> +}
> +
>  const struct rkvdec_coded_fmt_ops rkvdec_h264_fmt_ops = {
>  	.adjust_fmt = rkvdec_h264_adjust_fmt,
>  	.start = rkvdec_h264_start,
>  	.stop = rkvdec_h264_stop,
>  	.run = rkvdec_h264_run,
>  	.try_ctrl = rkvdec_h264_try_ctrl,
> +	.check_error_info = rkvdec_h264_check_error_info,
>  };

Actually I'm not sure I fully understand what you are expecting the
userspace to do with the information that there was an (HW!) error,
which might or might not be bitstrean related. Resending the
corrupted(?) frame until the HW fully hangs?
As the interrupt reports an HW error it should (at least also) be
handled driver-side and the HW is known not to be able to fully reset
itself in case of an error.
I think this will make behavior worse than it is now (for real-life
users) where errors are eventually just ignored.

Alex