From: Brian Niebuhr <[email protected]> Use a dummy param slot linked to itself to take care of the extra "sync event" that gets sent to EDMA controller after the last byte has been transferred.
The dummy PaRAM slot that is linked to the actual DMA PaRAM slot "absorbs" this event and prevents a EDMA CC error to be asserted. Without this provision, the EDMA CC error would be asserted because the channel PaRAM would be empty after the transfer and EDMA would not know what to make out of the extra sync event. Signed-off-by: Brian Niebuhr <[email protected]> Tested-By: Michael Williamson <[email protected]> Signed-off-by: Sekhar Nori <[email protected]> --- drivers/spi/davinci_spi.c | 28 +++++++++++++++++++++++++--- 1 files changed, 25 insertions(+), 3 deletions(-) diff --git a/drivers/spi/davinci_spi.c b/drivers/spi/davinci_spi.c index 6db4786..975c2a2 100644 --- a/drivers/spi/davinci_spi.c +++ b/drivers/spi/davinci_spi.c @@ -116,6 +116,7 @@ struct davinci_spi_dma { int dma_tx_channel; int dma_rx_channel; + int dummy_param_slot; enum dma_event_q eventq; struct completion dma_tx_completion; @@ -697,6 +698,8 @@ static int davinci_spi_bufs_dma(struct spi_device *spi, struct spi_transfer *t) param.src_dst_cidx = 0; param.ccnt = 1; edma_write_slot(davinci_spi_dma->dma_tx_channel, ¶m); + edma_link(davinci_spi_dma->dma_tx_channel, + davinci_spi_dma->dummy_param_slot); /* * Receive DMA setup @@ -779,19 +782,37 @@ static int davinci_spi_request_dma(struct davinci_spi_dma *davinci_spi_dma) davinci_spi_dma->eventq); if (r < 0) { pr_err("Unable to request DMA channel for SPI RX\n"); - return -EAGAIN; + r = -EAGAIN; + goto rx_dma_failed; } r = edma_alloc_channel(davinci_spi_dma->dma_tx_channel, davinci_spi_dma_tx_callback, davinci_spi_dma, davinci_spi_dma->eventq); if (r < 0) { - edma_free_channel(davinci_spi_dma->dma_rx_channel); pr_err("Unable to request DMA channel for SPI TX\n"); - return -EAGAIN; + r = -EAGAIN; + goto tx_dma_failed; } + r = edma_alloc_slot(EDMA_CTLR(davinci_spi_dma->dma_tx_channel), + EDMA_SLOT_ANY); + if (r < 0) { + pr_err("Unable to request SPI TX DMA param slot\n"); + r = -EAGAIN; + goto param_failed; + } + davinci_spi_dma->dummy_param_slot = r; + edma_link(davinci_spi_dma->dummy_param_slot, + davinci_spi_dma->dummy_param_slot); + return 0; +param_failed: + edma_free_channel(davinci_spi_dma->dma_tx_channel); +tx_dma_failed: + edma_free_channel(davinci_spi_dma->dma_rx_channel); +rx_dma_failed: + return r; } /** @@ -970,6 +991,7 @@ static int davinci_spi_probe(struct platform_device *pdev) free_dma: edma_free_channel(davinci_spi->dma_channels.dma_tx_channel); edma_free_channel(davinci_spi->dma_channels.dma_rx_channel); + edma_free_slot(davinci_spi->dma_channels.dummy_param_slot); free_clk: clk_disable(davinci_spi->clk); clk_put(davinci_spi->clk); -- 1.7.3.2 ------------------------------------------------------------------------------ Beautiful is writing same markup. Internet Explorer 9 supports standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3. Spend less time writing and rewriting code and more time creating great experiences on the web. Be a part of the beta today http://p.sf.net/sfu/msIE9-sfdev2dev _______________________________________________ spi-devel-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/spi-devel-general
