From 57c5c28dbc835c67a9c23912bab56b7f165e7715 Mon Sep 17 00:00:00 2001 From: Eero Nurkkala Date: Wed, 29 Jul 2009 15:02:12 -0700 Subject: [PATCH] spi: omap2_mcspi rxdma bugfix When data is read through DMA, the last element must be read separately through the RX register. It cannot be transferred by the DMA. For further details see e.g. OMAP35x TRM (table 19-16). Without the fix the driver causes extra clocks to be clocked to the bus after DMA RX operations. This can cause interesting behaviour with some devices. Signed-off-by: Juuso Oikarinen Signed-off-by: Eero Nurkkala [aaro.koskinen@nokia.com: Simplified the patch while keeping the idea.] Signed-off-by: Aaro Koskinen Signed-off-by: David Brownell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/spi/omap2_mcspi.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c index 2b64091b0f1f..9b80ad36dbba 100644 --- a/drivers/spi/omap2_mcspi.c +++ b/drivers/spi/omap2_mcspi.c @@ -272,7 +272,7 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer) if (rx != NULL) { omap_set_dma_transfer_params(mcspi_dma->dma_rx_channel, - data_type, element_count, 1, + data_type, element_count - 1, 1, OMAP_DMA_SYNC_ELEMENT, mcspi_dma->dma_rx_sync_dev, 1); @@ -303,6 +303,25 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer) if (rx != NULL) { wait_for_completion(&mcspi_dma->dma_rx_completion); dma_unmap_single(NULL, xfer->rx_dma, count, DMA_FROM_DEVICE); + omap2_mcspi_set_enable(spi, 0); + if (likely(mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHSTAT0) + & OMAP2_MCSPI_CHSTAT_RXS)) { + u32 w; + + w = mcspi_read_cs_reg(spi, OMAP2_MCSPI_RX0); + if (word_len <= 8) + ((u8 *)xfer->rx_buf)[element_count - 1] = w; + else if (word_len <= 16) + ((u16 *)xfer->rx_buf)[element_count - 1] = w; + else /* word_len <= 32 */ + ((u32 *)xfer->rx_buf)[element_count - 1] = w; + } else { + dev_err(&spi->dev, "DMA RX last word empty"); + count -= (word_len <= 8) ? 1 : + (word_len <= 16) ? 2 : + /* word_len <= 32 */ 4; + } + omap2_mcspi_set_enable(spi, 1); } return count; } -- 2.20.1