Am 18.03.2013 22:22, schrieb Mauro Carvalho Chehab: > 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. Ok, I finally had the chance to test with a HVR-930C, but it seems my device () is different. It has no slave device at i2c address 0x82, so I can't test this part. Btw, which slave device is this ? Removing the temporary switches to bus A makes no difference (as expected). > 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. Do you want me to send patches to remove these writes ? Which i2c speed settings do you suggest for the HVR-930C and the HTC-Stick (board settings: EM28XX_I2C_FREQ_400_KHZ, code overwrites it with EM28XX_I2C_FREQ_100_KHZ) ? Regards, Frank -- 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
