Re: [PATCH] AVerTV MCE 116 Plus radio

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

On Tue, Oct 06, 2009 at 11:11:59AM +0300, Aleksandr V. Piskunov wrote:
> On Tue, Oct 06, 2009 at 11:04:06AM +0300, Aleksandr V. Piskunov wrote:
> > Added FM radio support to Avermedia AVerTV MCE 116 Plus card
> > 
> 
> What leaves me puzzled, radio only works ok with ivtv newi2c=1
> 
> With default newi2c audio is tinny, metallic, with some strange static.
> Similar problem with pvr-150 was reported years ago, guess issue is still
> unresolved, perhaps something with cx25840..

This particular "tinny" audio problem is definitely I2C speed related, to be
more precise, audio only goes bad if i2c-algo-bit is being run with udelay
less than 15, i.e. i2c bus frequency is higher than 30 KHz.

So with default udelay=10 or udelay=5 (optimal for IR reciever on that board)
radio goes bad. Running with newi2c=1 is ok, but again it isn't optimal for IR
reciever on AVerTV M116.

I2C reads/writes to cx25840 themself are ok, verified using register readback
after each write/write4. Problem seems to be that with cx25840 register writes
coming too fast on higher i2c bus speed, switching register 0x808 _from_ 
TV standard autodetection mode (0xff) _to_ FM radio mode (0xf9) leaves chip 
audio detection routine in inconsistent state.

The only solution I found is to do standard routine (assert_reset + write +
deassert_reset) followed by 50ms delay and another reset.

Following patch works_for_me, can be improved to only delay/doublereset when
really needed, etc. Andy, could you comment/review?

diff --git a/linux/drivers/media/video/cx25840/cx25840-core.c b/linux/drivers/media/video/cx25840/cx25840-core.c
--- a/linux/drivers/media/video/cx25840/cx25840-core.c
+++ b/linux/drivers/media/video/cx25840/cx25840-core.c
@@ -626,7 +642,13 @@
 	if (state->radio) {
 		cx25840_write(client, 0x808, 0xf9);
 		cx25840_write(client, 0x80b, 0x00);
-	}
+		/* Double reset cx2384x after setting FM radio mode, helps to
+		   avoid "tinny" audio when ivtv I2C bus is being run on
+		   frequency higher than 30 KHz */
+		cx25840_and_or(client, 0x810, ~0x01, 0);
+		msleep(50);
+		cx25840_and_or(client, 0x810, ~0x01, 1);
+	}	
 	else if (std & V4L2_STD_525_60) {
 		/* Certain Hauppauge PVR150 models have a hardware bug
 		   that causes audio to drop out. For these models the