Subject: Re: [PATCH v5 00/39] i.MX Media Driver
To: Russell King - ARM Linux <linux@armlinux.org.uk>
References: <1489121599-23206-1-git-send-email-steve_longerbeam@mentor.com>
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Cc: mark.rutland@arm.com, andrew-ct.chen@mediatek.com,
        minghsiu.tsai@mediatek.com, nick@shmanahar.org,
        songjun.wu@microchip.com, hverkuil@xs4all.nl, pavel@ucw.cz,
        shuah@kernel.org, devel@driverdev.osuosl.org,
        markus.heiser@darmarIT.de,
        Steve Longerbeam <steve_longerbeam@mentor.com>, robert.jarzmik@free.fr,
        geert@linux-m68k.org, p.zabel@pengutronix.de,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        kernel@pengutronix.de, arnd@arndb.de, tiffany.lin@mediatek.com,
        bparrot@ti.com, robh+dt@kernel.org, horms+renesas@verge.net.au,
        mchehab@kernel.org, laurent.pinchart+renesas@ideasonboard.com,
        linux-arm-kernel@lists.infradead.org,
        niklas.soderlund+renesas@ragnatech.se, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org, jean-christophe.trotin@st.com,
        sakari.ailus@linux.intel.com, fabio.estevam@nxp.com,
        shawnguo@kernel.org, sudipm.mukherjee@gmail.com
From: Steve Longerbeam <slongerbeam@gmail.com>
Message-ID: <b8c7bdeb-ed34-4d08-39e5-4256c3671ab1@gmail.com>
Date: Tue, 14 Mar 2017 10:29:07 -0700
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On 03/12/2017 02:09 PM, Russell King - ARM Linux wrote:
> On Sun, Mar 12, 2017 at 08:40:37PM +0000, Russell King - ARM Linux wrote:
>> On Sun, Mar 12, 2017 at 01:36:32PM -0700, Steve Longerbeam wrote:
>>> But hold on, if my logic is correct, then why did the CSI power-off
>>> get reached in your case, multiple times? Yes I think there is a bug,
>>> link_notify() is not checking if the link has already been disabled.
>>> I will fix this. But I'm surprised media core's link_notify handling
>>> doesn't do this.
>> Well, I think there's something incredibly fishy going on here.  I
>> turned that dev_dbg() at the top of the function into a dev_info(),
>> and I get:
>>
>> root@hbi2ex:~# dmesg |grep -A2 imx-ipuv3-csi
>> [   53.370949] imx-ipuv3-csi imx-ipuv3-csi.0: power OFF
>> [   53.371015] ------------[ cut here ]------------
>> [   53.371075] WARNING: CPU: 0 PID: 1515 at drivers/staging/media/imx/imx-media-csi.c:806 csi_s_power+0xb8/0xd0 [imx_media_csi]
>> --
>> [   53.372624] imx-ipuv3-csi imx-ipuv3-csi.0: power OFF
>> [   53.372637] ------------[ cut here ]------------
>> [   53.372663] WARNING: CPU: 0 PID: 1515 at drivers/staging/media/imx/imx-media-csi.c:806 csi_s_power+0xb8/0xd0 [imx_media_csi]
>>
>> There isn't a power on event being generated before these two power
>> off events.  I don't see a power on event even when I attempt to
>> start streaming either (which fails due to the lack of bayer
>> support.)
> Found it - my imx219 driver returns '1' from its s_power function when
> powering up, which triggers a bug in your code - when imx_media_set_power()
> fails to power up, you call imx_media_set_power() telling it to power
> everything off - including devices that are already powered off.

Yep, there's a bug in the error cleanup in imx_media_pipeline_set_power().
On error, it needs to backout by calling s_power(off) as it is doing, 
but not
through the whole pipeline, but needs to stop at the subdev encountered
just before the subdev that failed. This was causing the s_power() 
imbalance.
I will fix.


>
> This is really bad news - s_power() may be called via other paths,
> such as when the subdev is opened.

I don't think that is a problem, as long as power_count is working
as it should, and the caller from the other paths has not created an
imbalance.

Steve