http://www.mjmwired.net/kernel/Documentation/DMA-mapping.txt 2010/1/29 yogeshwar sonawane <yogyas@xxxxxxxxx>: > Hi all, > > Following questions can be of naïve nature. Kindly, help me to clarify > the points. > Thanks in Advance. > > 1) Consider a situation where a PCIe device has requested a DMA Write > operation followed by an MSI based interrupt. Upon receiving the > interrupt, the software will read/check the DMAed data. Now, even if > the device is guaranteeing the ordering between the two (issuing one > after the other), whether the I/O controller OR chipset can > reorder/buffer them? This may result into getting interrupt before the > data is DMAed resulting into software reading invalid data. Here data > is residing into internal buffers of I/O controller and CPU is trying > to read from memory. Whether such DMA reordering can happen/is allowed > at all? Whether I/O controller can employ such intelligence(any kind > of DMA reordering) for gaining some performance advantage? Mainly, > focus is on high-end server class platforms having 8 or 16 cores with > many peripherals. > > 2) If above situation is at all possible, then to avoid such situation > is the responsibility of the device or the driver for that device? > Mainly, both the components (device and driver) expected to be generic > in nature (platform, I/O controller independent). > > 3) In continuation, if driver has to handle such situations, then how > to handle such cases in Linux device driver? Any API is there for > pending DMA flush/sync in I/O controller? I am aware of rmb(), wmb() & > mb() which ensures ordering from CPU side i.e. slave read/writes. > Anythings similar for DMA operations ? > > Kindly, update me if i am missing something. > > Any info,link or reference will be of great help. > > Thanks and Regards, > Yogeshwar > > -- > To unsubscribe from this list: send an email with > "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx > Please read the FAQ at http://kernelnewbies.org/FAQ > > -- Best Regards Lin -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
