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Message-Id: <20250624-james-nxp-spi-dma-v3-4-e7d574f5f62c@linaro.org>
Date: Tue, 24 Jun 2025 11:35:34 +0100
From: James Clark <james.clark@...aro.org>
To: Vladimir Oltean <olteanv@...il.com>, Mark Brown <broonie@...nel.org>,
Vladimir Oltean <vladimir.oltean@....com>, Arnd Bergmann <arnd@...db.de>,
Larisa Grigore <larisa.grigore@....com>, Frank Li <Frank.li@....com>,
Christoph Hellwig <hch@....de>
Cc: linux-spi@...r.kernel.org, imx@...ts.linux.dev,
linux-kernel@...r.kernel.org, James Clark <james.clark@...aro.org>
Subject: [PATCH v3 4/6] spi: spi-fsl-dspi: Use non-coherent memory for DMA
Using coherent memory here isn't functionally necessary. Because the
change to use non-coherent memory isn't overly complex and only a few
synchronization points are required, we might as well do it while fixing
up some other DMA issues.
Suggested-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: James Clark <james.clark@...aro.org>
---
drivers/spi/spi-fsl-dspi.c | 56 +++++++++++++++++++++++++++++-----------------
1 file changed, 36 insertions(+), 20 deletions(-)
diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 8212c4193536..172eb9929de1 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -492,11 +492,20 @@ static void dspi_push_rx(struct fsl_dspi *dspi, u32 rxdata)
}
#if IS_ENABLED(CONFIG_HAS_DMA)
+
+static int dspi_dma_transfer_size(struct fsl_dspi *dspi)
+{
+ return dspi->words_in_flight * DMA_SLAVE_BUSWIDTH_4_BYTES;
+}
+
static void dspi_tx_dma_callback(void *arg)
{
struct fsl_dspi *dspi = arg;
struct fsl_dspi_dma *dma = dspi->dma;
+ struct device *dev = &dspi->pdev->dev;
+ dma_sync_single_for_cpu(dev, dma->tx_dma_phys,
+ dspi_dma_transfer_size(dspi), DMA_TO_DEVICE);
complete(&dma->cmd_tx_complete);
}
@@ -504,9 +513,13 @@ static void dspi_rx_dma_callback(void *arg)
{
struct fsl_dspi *dspi = arg;
struct fsl_dspi_dma *dma = dspi->dma;
+ struct device *dev = &dspi->pdev->dev;
int i;
if (dspi->rx) {
+ dma_sync_single_for_cpu(dev, dma->rx_dma_phys,
+ dspi_dma_transfer_size(dspi),
+ DMA_FROM_DEVICE);
for (i = 0; i < dspi->words_in_flight; i++)
dspi_push_rx(dspi, dspi->dma->rx_dma_buf[i]);
}
@@ -516,6 +529,7 @@ static void dspi_rx_dma_callback(void *arg)
static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
{
+ size_t size = dspi_dma_transfer_size(dspi);
struct device *dev = &dspi->pdev->dev;
struct fsl_dspi_dma *dma = dspi->dma;
int time_left;
@@ -524,10 +538,9 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
for (i = 0; i < dspi->words_in_flight; i++)
dspi->dma->tx_dma_buf[i] = dspi_pop_tx_pushr(dspi);
+ dma_sync_single_for_device(dev, dma->tx_dma_phys, size, DMA_TO_DEVICE);
dma->tx_desc = dmaengine_prep_slave_single(dma->chan_tx,
- dma->tx_dma_phys,
- dspi->words_in_flight *
- DMA_SLAVE_BUSWIDTH_4_BYTES,
+ dma->tx_dma_phys, size,
DMA_MEM_TO_DEV,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!dma->tx_desc) {
@@ -542,10 +555,10 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
return -EINVAL;
}
+ dma_sync_single_for_device(dev, dma->rx_dma_phys, size,
+ DMA_FROM_DEVICE);
dma->rx_desc = dmaengine_prep_slave_single(dma->chan_rx,
- dma->rx_dma_phys,
- dspi->words_in_flight *
- DMA_SLAVE_BUSWIDTH_4_BYTES,
+ dma->rx_dma_phys, size,
DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!dma->rx_desc) {
@@ -642,17 +655,17 @@ static int dspi_request_dma(struct fsl_dspi *dspi, phys_addr_t phy_addr)
goto err_tx_channel;
}
- dma->tx_dma_buf = dma_alloc_coherent(dma->chan_tx->device->dev,
- dma_bufsize, &dma->tx_dma_phys,
- GFP_KERNEL);
+ dma->tx_dma_buf = dma_alloc_noncoherent(dma->chan_tx->device->dev,
+ dma_bufsize, &dma->tx_dma_phys,
+ DMA_TO_DEVICE, GFP_KERNEL);
if (!dma->tx_dma_buf) {
ret = -ENOMEM;
goto err_tx_dma_buf;
}
- dma->rx_dma_buf = dma_alloc_coherent(dma->chan_rx->device->dev,
- dma_bufsize, &dma->rx_dma_phys,
- GFP_KERNEL);
+ dma->rx_dma_buf = dma_alloc_noncoherent(dma->chan_rx->device->dev,
+ dma_bufsize, &dma->rx_dma_phys,
+ DMA_FROM_DEVICE, GFP_KERNEL);
if (!dma->rx_dma_buf) {
ret = -ENOMEM;
goto err_rx_dma_buf;
@@ -687,11 +700,12 @@ static int dspi_request_dma(struct fsl_dspi *dspi, phys_addr_t phy_addr)
return 0;
err_slave_config:
- dma_free_coherent(dma->chan_rx->device->dev,
- dma_bufsize, dma->rx_dma_buf, dma->rx_dma_phys);
+ dma_free_noncoherent(dma->chan_rx->device->dev, dma_bufsize,
+ dma->rx_dma_buf, dma->rx_dma_phys,
+ DMA_FROM_DEVICE);
err_rx_dma_buf:
- dma_free_coherent(dma->chan_tx->device->dev,
- dma_bufsize, dma->tx_dma_buf, dma->tx_dma_phys);
+ dma_free_noncoherent(dma->chan_tx->device->dev, dma_bufsize,
+ dma->tx_dma_buf, dma->tx_dma_phys, DMA_TO_DEVICE);
err_tx_dma_buf:
dma_release_channel(dma->chan_tx);
err_tx_channel:
@@ -712,14 +726,16 @@ static void dspi_release_dma(struct fsl_dspi *dspi)
return;
if (dma->chan_tx) {
- dma_free_coherent(dma->chan_tx->device->dev, dma_bufsize,
- dma->tx_dma_buf, dma->tx_dma_phys);
+ dma_free_noncoherent(dma->chan_tx->device->dev, dma_bufsize,
+ dma->tx_dma_buf, dma->tx_dma_phys,
+ DMA_TO_DEVICE);
dma_release_channel(dma->chan_tx);
}
if (dma->chan_rx) {
- dma_free_coherent(dma->chan_rx->device->dev, dma_bufsize,
- dma->rx_dma_buf, dma->rx_dma_phys);
+ dma_free_noncoherent(dma->chan_rx->device->dev, dma_bufsize,
+ dma->rx_dma_buf, dma->rx_dma_phys,
+ DMA_FROM_DEVICE);
dma_release_channel(dma->chan_rx);
}
}
--
2.34.1
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