Messages in this thread | | | From | Richard Genoud <> | Date | Mon, 21 Oct 2013 10:26:03 +0200 | Subject | Re: [BUG] spi/spi-atmel: DMA rx buffer corruption with SPI_IOC_MESSAGE |
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2013/10/21 Yang, Wenyou <Wenyou.Yang@atmel.com>: > Hi Richard, > >> -----Original Message----- >> From: Richard Genoud [mailto:richard.genoud@gmail.com] >> Sent: 2013年10月17日 19:01 >> To: Yang, Wenyou >> Cc: linux-spi@vger.kernel.org; linux-kernel@vger.kernel.org; Ferre, Nicolas; >> Mark Brown >> Subject: Re: [BUG] spi/spi-atmel: DMA rx buffer corruption with >> SPI_IOC_MESSAGE >> >> 2013/10/8 Richard Genoud <richard.genoud@gmail.com>: >> > 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?
Hi Wenyou,
I'm not using any slave device, I'm just setting the MISO pin to 3.3V, then I execute the C code ( https://lkml.org/lkml/2013/10/8/329 ) So, we should only receive 0xFF in the buffer. But i'm getting : aa aa aa aa aa aa aa aa aa aa aa aa aa aa ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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