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Commit 8da0859a authored by David Brownell's avatar David Brownell Committed by Linus Torvalds
Browse files

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: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Acked-by: default avatarHaavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 698ca47e

drivers/spi/atmel_spi.c

+45 −12
Original line number Diff line number Diff line
@@ -184,18 +184,39 @@ static void atmel_spi_next_message(struct spi_master *master) 
	atmel_spi_next_xfer(master, msg);

}



static void

/*

 * For DMA, tx_buf/tx_dma have the same relationship as rx_buf/rx_dma:

 *  - The buffer is either valid for CPU access, else NULL

 *  - If the buffer is valid, so is its DMA addresss

 *

 * This driver manages the dma addresss unless message->is_dma_mapped.

 */

static int

atmel_spi_dma_map_xfer(struct atmel_spi *as, struct spi_transfer *xfer)

{

	struct device	*dev = &as->pdev->dev;



	xfer->tx_dma = xfer->rx_dma = INVALID_DMA_ADDRESS;

	if (xfer->tx_buf)

		xfer->tx_dma = dma_map_single(&as->pdev->dev,

	if (xfer->tx_buf) {

		xfer->tx_dma = dma_map_single(dev,

				(void *) xfer->tx_buf, xfer->len,

				DMA_TO_DEVICE);

	if (xfer->rx_buf)

		xfer->rx_dma = dma_map_single(&as->pdev->dev,

		if (dma_mapping_error(xfer->tx_dma))

			return -ENOMEM;

	}

	if (xfer->rx_buf) {

		xfer->rx_dma = dma_map_single(dev,

				xfer->rx_buf, xfer->len,

				DMA_FROM_DEVICE);

		if (dma_mapping_error(xfer->tx_dma)) {

			if (xfer->tx_buf)

				dma_unmap_single(dev,

						xfer->tx_dma, xfer->len,

						DMA_TO_DEVICE);

			return -ENOMEM;

		}

	}

	return 0;

}



static void atmel_spi_dma_unmap_xfer(struct spi_master *master,
@@ -398,8 +419,9 @@ static int atmel_spi_setup(struct spi_device *spi) 
		scbr = ((bus_hz + spi->max_speed_hz - 1)

			/ spi->max_speed_hz);

		if (scbr >= (1 << SPI_SCBR_SIZE)) {

			dev_dbg(&spi->dev, "setup: %d Hz too slow, scbr %u\n",

					spi->max_speed_hz, scbr);

			dev_dbg(&spi->dev,

				"setup: %d Hz too slow, scbr %u; min %ld Hz\n",

				spi->max_speed_hz, scbr, bus_hz/255);

			return -EINVAL;

		}

	} else
@@ -465,12 +487,19 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg) 
			dev_dbg(&spi->dev, "no protocol options yet\n");

			return -ENOPROTOOPT;

		}

	}



	/* scrub dcache "early" */

		/*

		 * DMA map early, for performance (empties dcache ASAP) and

		 * better fault reporting.  This is a DMA-only driver.

		 *

		 * NOTE that if dma_unmap_single() ever starts to do work on

		 * platforms supported by this driver, we would need to clean

		 * up mappings for previously-mapped transfers.

		 */

		if (!msg->is_dma_mapped) {

		list_for_each_entry(xfer, &msg->transfers, transfer_list)

			atmel_spi_dma_map_xfer(as, xfer);

			if (atmel_spi_dma_map_xfer(as, xfer) < 0)

				return -ENOMEM;

		}

	}



	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
@@ -537,6 +566,10 @@ static int __init atmel_spi_probe(struct platform_device *pdev) 


	as = spi_master_get_devdata(master);



	/*

	 * Scratch buffer is used for throwaway rx and tx data.

	 * It's coherent to minimize dcache pollution.

	 */

	as->buffer = dma_alloc_coherent(&pdev->dev, BUFFER_SIZE,

					&as->buffer_dma, GFP_KERNEL);

	if (!as->buffer)