atmel_spi: minor updates
Minor updates to atmel_spi: - DMA: * Comments to explain the DMA policies * Report any mapping errors from spi_transfer() * Remove extra loop for DMA mapping - Diagnostics: report minimum clock rate, if we need to reject a spi_setup() request because that rate is too low. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -184,18 +184,39 @@ static void atmel_spi_next_message(struct spi_master *master)
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atmel_spi_next_xfer(master, msg);
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}
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static void
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/*
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* For DMA, tx_buf/tx_dma have the same relationship as rx_buf/rx_dma:
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* - The buffer is either valid for CPU access, else NULL
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* - If the buffer is valid, so is its DMA addresss
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*
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* This driver manages the dma addresss unless message->is_dma_mapped.
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*/
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static int
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atmel_spi_dma_map_xfer(struct atmel_spi *as, struct spi_transfer *xfer)
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{
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struct device *dev = &as->pdev->dev;
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xfer->tx_dma = xfer->rx_dma = INVALID_DMA_ADDRESS;
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if (xfer->tx_buf)
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xfer->tx_dma = dma_map_single(&as->pdev->dev,
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if (xfer->tx_buf) {
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xfer->tx_dma = dma_map_single(dev,
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(void *) xfer->tx_buf, xfer->len,
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DMA_TO_DEVICE);
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if (xfer->rx_buf)
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xfer->rx_dma = dma_map_single(&as->pdev->dev,
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if (dma_mapping_error(xfer->tx_dma))
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return -ENOMEM;
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}
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if (xfer->rx_buf) {
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xfer->rx_dma = dma_map_single(dev,
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xfer->rx_buf, xfer->len,
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DMA_FROM_DEVICE);
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if (dma_mapping_error(xfer->tx_dma)) {
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if (xfer->tx_buf)
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dma_unmap_single(dev,
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xfer->tx_dma, xfer->len,
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DMA_TO_DEVICE);
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return -ENOMEM;
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}
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}
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return 0;
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}
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static void atmel_spi_dma_unmap_xfer(struct spi_master *master,
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@ -398,8 +419,9 @@ static int atmel_spi_setup(struct spi_device *spi)
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scbr = ((bus_hz + spi->max_speed_hz - 1)
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/ spi->max_speed_hz);
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if (scbr >= (1 << SPI_SCBR_SIZE)) {
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dev_dbg(&spi->dev, "setup: %d Hz too slow, scbr %u\n",
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spi->max_speed_hz, scbr);
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dev_dbg(&spi->dev,
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"setup: %d Hz too slow, scbr %u; min %ld Hz\n",
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spi->max_speed_hz, scbr, bus_hz/255);
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return -EINVAL;
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}
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} else
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@ -465,12 +487,19 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
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dev_dbg(&spi->dev, "no protocol options yet\n");
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return -ENOPROTOOPT;
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}
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}
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/* scrub dcache "early" */
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if (!msg->is_dma_mapped) {
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list_for_each_entry(xfer, &msg->transfers, transfer_list)
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atmel_spi_dma_map_xfer(as, xfer);
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/*
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* DMA map early, for performance (empties dcache ASAP) and
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* better fault reporting. This is a DMA-only driver.
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*
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* NOTE that if dma_unmap_single() ever starts to do work on
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* platforms supported by this driver, we would need to clean
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* up mappings for previously-mapped transfers.
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*/
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if (!msg->is_dma_mapped) {
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if (atmel_spi_dma_map_xfer(as, xfer) < 0)
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return -ENOMEM;
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}
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}
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list_for_each_entry(xfer, &msg->transfers, transfer_list) {
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@ -537,6 +566,10 @@ static int __init atmel_spi_probe(struct platform_device *pdev)
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as = spi_master_get_devdata(master);
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/*
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* Scratch buffer is used for throwaway rx and tx data.
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* It's coherent to minimize dcache pollution.
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*/
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as->buffer = dma_alloc_coherent(&pdev->dev, BUFFER_SIZE,
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&as->buffer_dma, GFP_KERNEL);
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if (!as->buffer)
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