Em Wed, 06 Mar 2013 18:44:07 +0100 Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx> escreveu: > 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. There are some things there on the init sequence that can be cleaned/removed. Those sequences generally comes from observing what the original driver does. While it produces a working driver, in general, it is not optimized and part of the init sequence can be removed. Regards, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
