Hello, I write a pci linux driver, and after reviewing some examples in kernel, there is issue I am not sure about: DMA seems to follow the following steps in PCI: 1. driver allocate dma buffers and map them to BAR. 2. driver initialize device to be familiar with dma addresses. 3. tx from cpu to device: driver trigger dma, by writing into device BARs. 4. rx from device to cpu: device is responsible for triggering DMA (driver does not do anything here) 5. tx/rx completion: interrupt from DMA (in cpu) 6. interrupt handler of section 5 above checks that device finished tx/rx. Is the above understanding correct ? 1. As to 6, I am not sure about, is it that device knows that transaction is finished (DMA is in soc , not device) ? 2. How does device triggers DMA from device to cpu, is it by simply writing to BAR ? 3. How does device triggers DMA from cpu to device, is it by simply reading from BAR ? Thank you, Ran
