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

[Steve Longerbeam]

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