Re: tvp5150 regression after commit 9f924169c035

[Wolfram Sang <wsa@the-dreams.de>]

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On Wed, Feb 03, 2016 at 10:46:51AM -0300, Javier Martinez Canillas wrote:
> Hello Wolfram,
> 
> I've a issue with a I2C video decoder driver (drivers/media/i2c/tvp5150.c).
> 
> In v4.5-rc1, the driver gets I2C read / writes timeouts when accessing the
> device I2C registers:
> 
> tvp5150 1-005c: i2c i/o error: rc == -110
> tvp5150: probe of 1-005c failed with error -110
> 
> The driver used to work up to v4.4 so this is a regression in v4.5-rc1:
> 
> tvp5150 1-005c: tvp5151 (1.0) chip found @ 0xb8 (OMAP I2C adapter)
> tvp5150 1-005c: tvp5151 detected.
> 
> I tracked down to commit 9f924169c035 ("i2c: always enable RuntimePM for
> the adapter device") and reverting that commit makes things to work again.
> 
> The tvp5150 driver doesn't have runtime PM support but the I2C controller
> driver does (drivers/i2c/busses/i2c-omap.c) FWIW.
> 
> I tried adding runtime PM support to tvp5150 (basically calling pm_runtime
> enable/get on probe before the first I2C read to resume the controller) but
> that it did not work.
> 
> Not filling the OMAP I2C driver's runtime PM callbacks does not help either.
> 
> Any hints about the proper way to fix this issue?

Asking linux-pm for help:

The commit in question enables RuntimePM for the logical adapter device
which sits between the HW I2C controller and the I2C client device. This
adapter device has been used with pm_runtime_no_callbacks before
enabling RPM. Now, Alan explained to me that "suspend events will
propagate from the I2C clients all the way up to the adapter's parent."
with RPM enabled for the adapter device. Which should be a no-op if the
client doesn't do any PM at all? What do I miss?

Thanks,

   Wolfram


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