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Subject: Re: [PATCH v2 1/2] media: imx: csi: Disable CSI immediately after
 last EOF
To:     Philipp Zabel <p.zabel@pengutronix.de>, linux-media@vger.kernel.org
Cc:     stable@vger.kernel.org, Mauro Carvalho Chehab <mchehab@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "open list:STAGING SUBSYSTEM" <devel@driverdev.osuosl.org>,
        open list <linux-kernel@vger.kernel.org>
References: <20190117204912.28456-1-slongerbeam@gmail.com>
 <20190117204912.28456-2-slongerbeam@gmail.com>
 <1547807043.3375.3.camel@pengutronix.de>
From:   Steve Longerbeam <slongerbeam@gmail.com>
Message-ID: <56b43909-136b-fce0-e743-26cd6afd0eea@gmail.com>
Date:   Fri, 18 Jan 2019 11:01:35 -0800
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On 1/18/19 2:24 AM, Philipp Zabel wrote:
> On Thu, 2019-01-17 at 12:49 -0800, Steve Longerbeam wrote:
>> Disable the CSI immediately after receiving the last EOF before stream
>> off (and thus before disabling the IDMA channel).
>>
>> This fixes a complete system hard lockup on the SabreAuto when streaming
>> from the ADV7180, by repeatedly sending a stream off immediately followed
>> by stream on:
>>
>> while true; do v4l2-ctl  -d4 --stream-mmap --stream-count=3; done
>>
>> Eventually this either causes the system lockup or EOF timeouts at all
>> subsequent stream on, until a system reset.
>>
>> The lockup occurs when disabling the IDMA channel at stream off. Disabling
>> the CSI before disabling the IDMA channel appears to be a reliable fix for
>> the hard lockup.
>>
>> Fixes: 4a34ec8e470cb ("[media] media: imx: Add CSI subdev driver")
>>
>> Reported-by: Gaël PORTAY <gael.portay@collabora.com>
>> Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
>> Cc: stable@vger.kernel.org
>> ---
>> Changes in v2:
>> - restore an empty line
>> - Add Fixes: and Cc: stable
>> ---
>>   drivers/staging/media/imx/imx-media-csi.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/media/imx/imx-media-csi.c b/drivers/staging/media/imx/imx-media-csi.c
>> index e18f58f56dfb..e0f6f88e2e70 100644
>> --- a/drivers/staging/media/imx/imx-media-csi.c
>> +++ b/drivers/staging/media/imx/imx-media-csi.c
>> @@ -681,6 +681,8 @@ static void csi_idmac_stop(struct csi_priv *priv)
>>   	if (ret == 0)
>>   		v4l2_warn(&priv->sd, "wait last EOF timeout\n");
>>   
>> +	ipu_csi_disable(priv->csi);
>> +
> Can you add a short comment why this call is here? Since now
> csi_idmac_stop is kind of a misnomer and symmetry with csi(_idmac)_start
> is broken, I think this is a bit un-obvious.

Yeah. I think a cleaner, more symmetric solution would be to split up 
csi_idmac_stop.

>
> Also note that now the error path of csi_start() will now call
> ipu_csi_disable() while the CSI is disabled. This happens to work
> because that just calls ipu_module_disable(), which is not refcounted.

Thanks for catching. Splitting up csi_idmac_stop will fix this. Working 
on that.

Steve

>
>>   	devm_free_irq(priv->dev, priv->eof_irq, priv);
>>   	devm_free_irq(priv->dev, priv->nfb4eof_irq, priv);
>>   
>> @@ -793,9 +795,9 @@ static void csi_stop(struct csi_priv *priv)
>>   		/* stop the frame interval monitor */
>>   		if (priv->fim)
>>   			imx_media_fim_set_stream(priv->fim, NULL, false);
>> +	} else {
>> +		ipu_csi_disable(priv->csi);
>>   	}
>> -
>> -	ipu_csi_disable(priv->csi);
> Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
>
> regards
> Philipp