Re: [PATCH] af9013: fix i2c failures for dual-tuner devices

[Antti Palosaari <crope@iki.fi>]

On 01/20/2012 11:18 PM, Gordon Hecker wrote:
> This patch fixes the following error messages with a
> Terratec Cinergy T Stick Dual RC DVB-T device.
>
> af9013: i2c wr failed=-1 reg=d607 len=1
> af9015: command failed:2
> af9013: i2c rd failed=-1 reg=d607 len=1
> af9015: command failed:1
>
> It implements exclusive access to i2c for only one frontend at a time
> through a use-counter that is increased for each af9013_i2c_gate_ctrl-enable
> or i2c-read/write and decreased accordingly. The use-counter remains
> incremented after af9013_i2c_gate_ctrl-enable until the corresponding
> disable.
>
> Debug output was added.
>
> ToDo:
>   * Replace frontend by adapter (the dual-tuner devices do actually
>     provide two adapters with one frontend each)
>   * move af9013_i2c_gate_mutex, locked_fe, af9013_i2c_gate_ctrl_usecnt
>     to the usb device

Again that same issue. But after af9013 rewrote those should not be very 
significant problem... If you looked, as I can guess, AF9015 code you 
can see callbacks lock that are for resolving same issue. Almost all 
callbacks are locked, but I left few rarely called callbacks without 
lock due to performance point of view. You can guess it causes always 
latency to wait other thread finish callback...

I think you may resolve that just adding one or two callback lock more, 
likely for tuner init() and sleep().

I don't like that you are adding such code for the demod driver - 
problem is USB-bridge, its I2C adapter and firmware. Due to that such 
code should be in AF9015 driver. There has been originally two I2C 
adapters in af9015 but I removed those. And there is actually only one 
I2C adapter in AF9015.
See these for more info about I2C bus connections:
http://palosaari.fi/linux/v4l-dvb/controlling_tuner_af9015_dual_demod.txt
http://palosaari.fi/linux/v4l-dvb/controlling_tuner.txt

I think that piece of code is not very important and I dont like to see 
it in current af9013 driver. Do needed changes for af9015 instead.

regards
Antti

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