On Wednesday, September 17, 2014 at 04:50:34 PM, Yao Yuan wrote: [...] > > > > Would that mean that the "crashed" DMA would be running until the > > > > next transmission is scheduled ? > > > > > > [Yuan Yao] No, In fact any DMA timeout will result the failure of I2C > > > transmission and then it will turn to report the exception and wait > > > for next transmission. > > > > Can you tell when the next transmission will happen? What if I issue a > > single transmission and that one fails ? Will the DMA run until who knows > > when ? > > [Yuan Yao] > Sorry for my unclear description. In fact, During the DMA transmission if > an error happened or time out, DMA will stop at once and be disabled. > I just continue to route the TX and RX request to signal the DMA > controller. Because the DMA is disabled, it will ignore those signals. > > In a word, I just want to block the I2C TX, RX and interrupt signal when > DMA mode failed until the next I2C transmission start. So the I2C block is in error state until you clean it up upon next transmission? > In fact, the bit "I2CR_DMAEN" is a switch which decide whether I2C route > the TX, RX and interrupt signal to DMA controller. > > > > The only thing I worried about is I2C may still receive some feedbacks > > > after DMA timeout. In this case the feedbacks may lead to abnormal > > > state in PIO mode.But it will be ignored in DMA model. > > > That's why I tend to delay force-disable DMA until the next > > > transmission begin. Could you please give me some suggestion? > > > > No, this design just seems flawed to me. You should stop the DMA > > immediatelly if there is an error to avoid wasting resources and prevent > > possible other adverse effects. > > [Yuan Yao] > Yes, I have stopped the DMA immediately. However I keep the I2C DMA > single route. > > I don't have the exact evidence to prove that my design is acceptable. > So if you are sure it's flawed, I will change it in the next version(V8). I'm just trying to understand it. Best regards, Marek Vasut -- 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
