2013/10/8 Richard Genoud <[email protected]>: > Hi all, > > I finally found the bug I saw months ago, before "[PATCH v8 3/8] > spi/spi-atmel: add dmaengine support" was merged. > > Here it is: > > When the ioctl SPI_IOC_MESSAGE is used with small and big buffers, > the big RX buffer is corrupted with bytes from the big TX buffer. > (Small means size < DMA_MIN_BYTES, Big means size > DMA_MIN_BYTES) > > I'm attaching the test software that I used ( ./spi_test /dev/spidevx.x ) > > It fills 3 TX buffers with 0xAA pattern: a small, a big and a small again. > It reads in return 3 RX buffers. > The MISO pin has to be on 3.3v. > > It checks if the received buffers are filled with 0xFF (they should > be, as MISO is high). > And I've got a lot of buffers filled partially with 0xAA bytes. > > BUT, if you apply this patch: > ---8<---- > diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c > index 83cf609..cde42a4 100644 > --- a/drivers/spi/spi-atmel.c > +++ b/drivers/spi/spi-atmel.c > @@ -187,7 +187,7 @@ > /* use PIO for small transfers, avoiding DMA setup/teardown overhead and > * cache operations; better heuristics consider wordsize and bitrate. > */ > -#define DMA_MIN_BYTES 16 > +#define DMA_MIN_BYTES 0 > > struct atmel_spi_dma { > struct dma_chan *chan_rx; > ---8<---- > There's no error any more. > So there's something wrong happening when switching from/to pio > transfer to/from DMA. > > We didn't saw that at the time of the merge because we did the test > with a loop on MISO/MOSI, > so the RX buffer was corrupted with identical bytes. > > Best regards, > Richard.
Hi Wenyou, Did you have the opportunity to give it a test ? Thread: https://lkml.org/lkml/2013/10/8/329 Richard. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
