Hi Sascha, On Mon, 2015-03-30 at 19:23 +0200, Sascha Hauer wrote: > On Mon, Mar 30, 2015 at 04:14:12PM +0800, Eddie Huang wrote: > > Hi Sascha, > > > > > > > > [...] > > > > > > > + if (i2c->speed_hz > 400000) > > > > + control_reg |= I2C_CONTROL_RS; > > > > + if (i2c->op == I2C_MASTER_WRRD) > > > > + control_reg |= I2C_CONTROL_DIR_CHANGE | I2C_CONTROL_RS; > > > > + mtk_i2c_writew(control_reg, i2c, OFFSET_CONTROL); > > > > + > > > > + /* set start condition */ > > > > + if (i2c->speed_hz <= 100000) > > > > + mtk_i2c_writew(I2C_ST_START_CON, i2c, OFFSET_EXT_CONF); > > > > + else > > > > + mtk_i2c_writew(I2C_FS_START_CON, i2c, OFFSET_EXT_CONF); > > > > + > > > > + if (~control_reg & I2C_CONTROL_RS) > > > > + mtk_i2c_writew(I2C_DELAY_LEN, i2c, OFFSET_DELAY_LEN); > > > > > > speed <= 400000 here to make this more obvious? > > There are two cases, not only speed<=400000, but I2C_MASTER_WRRD. I tend > > to keep it. > > Still it looks strange. You only ever write this default value to the > register. Putting this register write under an if() seems bogus since > the same value will be in the register the next time this code is > executed. It looks like you should move this register write to some > initialization function. OK, move to mtk_i2c_init_hw function > > > > > + > > > > + /* Enable interrupt */ > > > > + mtk_i2c_writew(I2C_HS_NACKERR | I2C_ACKERR | I2C_TRANSAC_COMP, > > > > + i2c, OFFSET_INTR_MASK); > > > > > > Why do you enable/disable interrupts for each transfer? Enabling them > > > once and just acknowledge them in the interrupt handler should be > > > enough. > > This can avoid unwanted I2C interrupt. For example, I2C transfer error, > > and cause timeout, I2C driver report error to caller. Then I2C error > > interrupt happen. > > So isn't the same unwanted interrupt then just delayed until you enable > the interrupts again? Is this something that really happens or just > something you think that might happen? > Clear interrupt status before enable interrupt, so won't get unwanted interrupt again. I just think this might happen, and it's not harmful to enable/disable interrupt in transfer function and can get extra benefit to avoid unnecessary interrupt. Tegra I2C driver i2c-tegra.c also do the same thing. Eddie -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
