Hi Richard, > -----Original Message----- > From: Richard Genoud [mailto:[email protected]] > Sent: 2013年10月17日 19:01 > To: Yang, Wenyou > Cc: [email protected]; [email protected]; Ferre, Nicolas; > Mark Brown > Subject: Re: [BUG] spi/spi-atmel: DMA rx buffer corruption with > SPI_IOC_MESSAGE > > 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 I tried to reproduce it with this thread, but I didn't Which slave device did you use?
> > Richard. Best Regards, Wenyou Yang
