On Thu, 2014-11-13 at 19:31 +0100, Wolfram Sang wrote: > > MTK I2C HW has some limitation. > > 1. If the i2c_msg number is more than one, STOP will be issued instead of > > RS(Repeat Start) between each message. > > > > 2. Mediatek I2C controller support WRRD(write then read) mode, in WRRD > > mode the Repeat Start will be issued between 2 messages. > > In this driver if 2 messages is first write then read, the driver will > > combine 2 messages using Write-Read mode so the RS will be issued between > > the 2 messages. > > Ex: W/R/R, driver will combine first W/R and then R. > > > > 3. Due to HW limitation, in this version the max transfer data length is 255 > > in one message. > > This looks to me more like an SMBUS controller instead of I2C. Maybe you > should populate smbus_xfer rather than master_xfer? This is the HW limitation, we will try to workaround this in the separate patch. > > > MT8135 and MT6589 can control I2C pins on PMIC(MT6397) by setting the i2c > > registers in MT8135 side. > > I still didn't get this, even after reading the mail thread of old > series. Can someone maybe draw me a nice ASCII picture showing the setup > which is going on here? > 1. The DIR_PATH register is in MT8135. 2. All the registers used in the driver are in MT8135. 3. If want I2C wave go/from PMIC need to set the DIR_PATH register bit^0 to 1 extra. >From the picture: If MT8135 connected to PMIC(MT6397), when set the DIR_PATH register bit^0 to 1, the HW will transfer the i2c wave from pins(SDA4_pmic & SCL4_pmic) on MT6397 side. If want use pins(SDA4 & SCL4) on 8135 side directly, we should set the DIR_PATH register bit^0 to 0. _______ ________ | |______| | | | | PMIC | | 8135 |______| (6397)|___SDA4_pmic | | | |___SCL4_pmic !______! !_______! | | SDA4 SCL4 Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
