Re: [REVIEW] ivtv, ir-kbd-i2c: Explicit IR support for the AVerTV M116 for newer kernels

["Aleksandr V. Piskunov" <aleksandr.v.piskunov@gmail.com>]

> > Basicly during the I2C operation that reads scancode, controller seems
> > to stop processing input from IR sensor, resulting a loss of keypress.
> > 
> > So the solution(?) I found was to decrease the udelay in
> > ivtv_i2c_algo_template from 10 to 5. Guess it just doubles the frequency
> > of ivtv i2c bus or something like that. Problem went away, IR controller
> > is now working as expected.
> 
> That's a long standing error in the ivtv driver.  It ran the I2C bus at
> 1/(2*10 usec) = 50 kHz instead of the standard 100 kHz.
> 
> Technically any I2C device should be able to handle clock rates down to
> about DC IIRC; so there must be a bug in the IR microcontroller
> implementation.
> 
> Also the CX23416 errantly marks its PCI register space as cacheable
> which is probably wrong (see lspci output).  This may also be
> interfering with proper I2C operation with i2c_algo_bit depedning on the
> PCI bridges in your system.
> 
> > 
> > So question is:
> > 1) Is it ok to decrease udelay for this board?
> 
> Sure, I think.  It would actually run the ivtv I2C bus at the nominal
> clock rate specified by the I2C specification.
> 
> I never had any reason to change it, as I feared causing regressions in
> many well tested boards.
> 
> 
> > 2) If yes, how to do it right?
> 
> Try:
> 
> # modprobe ivtv newi2c=1
> 
> to see if that works first. 
> 

udelay=10, newi2c=0  => BAD
udelay=10, newi2c=1  => BAD
udelay=5,  newi2c=0  => OK
udelay=5,  newi2c=1  => BAD


newi2c=1 also throws some log messages, not sure if its ok or not.

Oct  5 11:41:16 moon kernel: [45430.916449] ivtv: Start initialization, version 1.4.1
Oct  5 11:41:16 moon kernel: [45430.916618] ivtv0: Initializing card 0
Oct  5 11:41:16 moon kernel: [45430.916628] ivtv0: Autodetected AVerTV MCE 116 Plus card (cx23416 based)
Oct  5 11:41:16 moon kernel: [45430.918887] ivtv 0000:03:06.0: PCI INT A -> GSI 20 (level, low) -> IRQ 20
Oct  5 11:41:16 moon kernel: [45430.919229] ivtv0:  i2c: i2c init
Oct  5 11:41:16 moon kernel: [45430.919234] ivtv0:  i2c: setting scl and sda to 1
Oct  5 11:41:16 moon kernel: [45430.937745] cx25840 0-0044: cx25843-23 found @ 0x88 (ivtv i2c driver #0)
Oct  5 11:41:16 moon kernel: [45430.949145] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.951628] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.954191] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.956724] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.959211] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.961749] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.964236] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.966722] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.966786] ivtv0:  i2c: i2c write to 43 failed
Oct  5 11:41:16 moon kernel: [45430.971106] tuner 0-0061: chip found @ 0xc2 (ivtv i2c driver #0)
Oct  5 11:41:16 moon kernel: [45430.974404] wm8739 0-001a: chip found @ 0x34 (ivtv i2c driver #0)
Oct  5 11:41:16 moon kernel: [45430.986328] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.988871] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.991355] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.993904] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.996427] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45430.998938] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.001477] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.003968] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.004053] ivtv0:  i2c: i2c write to 18 failed
Oct  5 11:41:16 moon kernel: [45431.011333] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.013883] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.016418] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.018911] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.021463] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.023937] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.026478] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.028998] ivtv0:  i2c: Slave did not ack
Oct  5 11:41:16 moon kernel: [45431.029063] ivtv0:  i2c: i2c write to 71 failed
Oct  5 11:41:16 moon kernel: [45431.031468] ivtv0:  i2c: Slave did not ack
....