On Thursday, September 18, 2014 at 05:46:04 PM, Yao Yuan wrote: > Marek Vasut wrote: > > 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? > > [Yuan Yao] > No, just DMAEN bit. > Other I2C error state will clean soon. > > > > 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. > > [Yuan Yao] > Both of us know that we should stop DMA immediately when issue happened. > The only argument is that I want to set the DMAEN bit just before the next > transmission starts. But you think when I stop the DMA I should set it at > the same time. The bit is the switch which is used to decide whether Rx > and Tx signal can be routed to DMA. In fact, I deeply think about what is > the difference between our arguments for those days. I think the two ways > are almost the same. Your way is more acceptable because people tend to > clear the DMA status just after stopping it. So I think your way is > better. OK, I am a bit lost, so let's see V8 and then go with that one I'd say. 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
