linux-kernel - Re: [PATCH v5 00/39] i.MX Media Driver

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Date:   Tue, 14 Mar 2017 10:29:07 -0700
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     mark.rutland@....com, andrew-ct.chen@...iatek.com,
        minghsiu.tsai@...iatek.com, nick@...anahar.org,
        songjun.wu@...rochip.com, hverkuil@...all.nl, pavel@....cz,
        shuah@...nel.org, devel@...verdev.osuosl.org,
        markus.heiser@...marIT.de,
        Steve Longerbeam <steve_longerbeam@...tor.com>,
        robert.jarzmik@...e.fr, geert@...ux-m68k.org,
        p.zabel@...gutronix.de, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, kernel@...gutronix.de, arnd@...db.de,
        tiffany.lin@...iatek.com, bparrot@...com, robh+dt@...nel.org,
        horms+renesas@...ge.net.au, mchehab@...nel.org,
        laurent.pinchart+renesas@...asonboard.com,
        linux-arm-kernel@...ts.infradead.org,
        niklas.soderlund+renesas@...natech.se, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, jean-christophe.trotin@...com,
        sakari.ailus@...ux.intel.com, fabio.estevam@....com,
        shawnguo@...nel.org, sudipm.mukherjee@...il.com
Subject: Re: [PATCH v5 00/39] i.MX Media Driver



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@...2ex:~# 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