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atmel_spi: minor updates

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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>
This commit is contained in:
David Brownell 2007-07-17 04:04:07 -07:00 committed by Linus Torvalds
parent 698ca47e8d
commit 8da0859a24
1 changed files with 45 additions and 12 deletions
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57
drivers/spi/atmel_spi.c
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@ -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" */
if (!msg->is_dma_mapped) {
list_for_each_entry(xfer, &msg->transfers, transfer_list)
atmel_spi_dma_map_xfer(as, xfer);
/*
* 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) {
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)