Am 05.03.2013 16:43, schrieb Devin Heitmueller:
> 2013/3/5 Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>:
>> The em2874 chips and upper have 2 buses. On all known devices, bus 0 is
>> currently used only by eeprom, and bus 1 for the rest. Add support to
>> register both buses.
> Did you add a mutex to ensure that both buses cannot be used at the
> same time? Because using the bus requires you to toggle a register
> (thus you cannot be using both busses at the same time), you cannot
> rely on the existing i2c adapter lock anymore.
>
> You don't want a situation where something is actively talking on bus
> 0, and then something else tries to talk on bus 1, flips the register
> bit and then the thread talking on bus 0 starts failing.
>
> Devin
Hmm... there are several writes to EM28XX_R06_I2C_CLK in em28xx-dvb...
See hauppauge_hvr930c_init(), terratec_h5_init() and
terratec_htc_stick_init().
These functions are called from em28xx_dvb_init() at module init.
Module init is async, so yes, this is (or could at least become) a
problem...
I wonder if we can't simply remove all those writes to
EM28XX_R06_I2C_CLK from em28xx-dvb.
This is what the functions are doing:
hauppauge_hvr930c_init()
...
em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x40);
msleep(10);
em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x44);
msleep(10);
... [init sequence for slave at address 0x82]
em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x44);
msleep(30);
em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x45);
msleep(10);
terratec_h5_init():
...
em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x40);
msleep(10);
em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x45);
msleep(10);
...
terratec_htc_stick_init()
...
em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x40);
msleep(10);
em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x44);
msleep(10);
...
All three boards are using the following settings:
.i2c_speed = EM2874_I2C_SECONDARY_BUS_SELECT |
EM28XX_I2C_CLK_WAIT_ENABLE | EM28XX_I2C_FREQ_400_KHZ = 0x45
So what these functions are doing is
- switch to bus A and do nothing fo 10ms
- overwrite board settings for reg 0x06 with a local value (clears
EM28XX_I2C_FREQ_400_KHZ permanently for the HTC-Stick !).
I can test the HVR-930C next week.
Regards,
Frank
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