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Subject[PATCH v2 6/6] spi: sun4i: add DMA transfers support
Date
DMA transfers are now available for sun4i-family SoCs.
The DMA mode is used automatically as soon as requested
transfer length is more than FIFO length.

Changes in v2:
1) Debug log enhancements.

Signed-off-by: Sergey Suloev <ssuloev@orpaltech.com>
---
drivers/spi/spi-sun4i.c | 299 ++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 277 insertions(+), 22 deletions(-)

diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
index d81d31c..dda7922 100644
--- a/drivers/spi/spi-sun4i.c
+++ b/drivers/spi/spi-sun4i.c
@@ -14,6 +14,8 @@
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
@@ -39,6 +41,7 @@
#define SUN4I_CTL_CPHA BIT(2)
#define SUN4I_CTL_CPOL BIT(3)
#define SUN4I_CTL_CS_ACTIVE_LOW BIT(4)
+#define SUN4I_CTL_DMA_DEDICATED BIT(5)
#define SUN4I_CTL_LMTF BIT(6)
#define SUN4I_CTL_TF_RST BIT(8)
#define SUN4I_CTL_RF_RST BIT(9)
@@ -58,6 +61,8 @@
#define SUN4I_INT_STA_REG 0x10

#define SUN4I_DMA_CTL_REG 0x14
+#define SUN4I_CTL_DMA_RF_READY BIT(0)
+#define SUN4I_CTL_DMA_TF_NOT_FULL BIT(10)

#define SUN4I_WAIT_REG 0x18

@@ -169,6 +174,13 @@ static inline void sun4i_spi_fill_fifo(struct sun4i_spi *sspi, int len)
}
}

+static bool sun4i_spi_can_dma(struct spi_master *master,
+ struct spi_device *spi,
+ struct spi_transfer *tfr)
+{
+ return tfr->len > SUN4I_FIFO_DEPTH;
+}
+
static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
{
struct sun4i_spi *sspi = spi_master_get_devdata(spi->master);
@@ -208,6 +220,11 @@ static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)

static size_t sun4i_spi_max_transfer_size(struct spi_device *spi)
{
+ struct spi_master *master = spi->master;
+
+ if (master->can_dma)
+ return SUN4I_MAX_XFER_SIZE;
+
return SUN4I_FIFO_DEPTH;
}

@@ -235,6 +252,164 @@ static int sun4i_spi_wait_for_transfer(struct spi_device *spi,
return 0;
}

+static void sun4i_spi_dma_callback(void *param)
+{
+ struct spi_master *master = param;
+
+ dev_dbg(&master->dev, "DMA transfer complete\n");
+ spi_finalize_current_transfer(master);
+}
+
+static int sun4i_spi_dmap_prep_tx(struct spi_master *master,
+ struct spi_transfer *tfr,
+ dma_cookie_t *cookie)
+{
+ struct dma_async_tx_descriptor *chan_desc = NULL;
+
+ chan_desc = dmaengine_prep_slave_sg(master->dma_tx,
+ tfr->tx_sg.sgl, tfr->tx_sg.nents,
+ DMA_TO_DEVICE,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ if (!chan_desc) {
+ dev_err(&master->dev,
+ "Couldn't prepare TX DMA slave\n");
+ return -EIO;
+ }
+
+ chan_desc->callback = sun4i_spi_dma_callback;
+ chan_desc->callback_param = master;
+
+ *cookie = dmaengine_submit(chan_desc);
+ dma_async_issue_pending(master->dma_tx);
+
+ return 0;
+}
+
+static int sun4i_spi_dmap_prep_rx(struct spi_master *master,
+ struct spi_transfer *tfr,
+ dma_cookie_t *cookie)
+{
+ struct dma_async_tx_descriptor *chan_desc = NULL;
+
+ chan_desc = dmaengine_prep_slave_sg(master->dma_rx,
+ tfr->rx_sg.sgl, tfr->rx_sg.nents,
+ DMA_FROM_DEVICE,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ if (!chan_desc) {
+ dev_err(&master->dev,
+ "Couldn't prepare RX DMA slave\n");
+ return -EIO;
+ }
+
+ chan_desc->callback = sun4i_spi_dma_callback;
+ chan_desc->callback_param = master;
+
+ *cookie = dmaengine_submit(chan_desc);
+ dma_async_issue_pending(master->dma_rx);
+
+ return 0;
+}
+
+static int sun4i_spi_transfer_one_dma(struct spi_device *spi,
+ struct spi_transfer *tfr)
+{
+ struct spi_master *master = spi->master;
+ struct sun4i_spi *sspi = spi_master_get_devdata(master);
+ dma_cookie_t tx_cookie = 0, rx_cookie = 0;
+ enum dma_status status;
+ int ret;
+ u32 reg = 0;
+
+ dev_dbg(&master->dev, "Using DMA mode for transfer\n");
+
+ /* Disable interrupts */
+ sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
+
+ if (sspi->tx_buf) {
+ ret = sun4i_spi_dmap_prep_tx(master, tfr, &tx_cookie);
+ if (ret)
+ goto out;
+
+ reg |= SUN4I_CTL_DMA_TF_NOT_FULL;
+ }
+
+ if (sspi->rx_buf) {
+ ret = sun4i_spi_dmap_prep_rx(master, tfr, &rx_cookie);
+ if (ret)
+ goto out;
+
+ reg |= SUN4I_CTL_DMA_RF_READY;
+ }
+
+ sun4i_spi_write(sspi, SUN4I_DMA_CTL_REG, reg);
+
+ /* Dedicated DMA requests */
+ sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_DMA_DEDICATED);
+
+ /* Start transfer */
+ sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_XCH);
+
+ /* Wait for completion */
+ ret = sun4i_spi_wait_for_transfer(spi, tfr);
+ if (ret)
+ goto out;
+
+ if (sspi->tx_buf && (status = dma_async_is_tx_complete(master->dma_tx,
+ tx_cookie, NULL, NULL))) {
+ dev_warn(&master->dev,
+ "DMA returned completion status of: %s\n",
+ status == DMA_ERROR ? "error" : "in progress");
+ }
+ if (sspi->rx_buf && (status = dma_async_is_tx_complete(master->dma_rx,
+ rx_cookie, NULL, NULL))) {
+ dev_warn(&master->dev,
+ "DMA returned completion status of: %s\n",
+ status == DMA_ERROR ? "error" : "in progress");
+ }
+
+out:
+ if (ret) {
+ dev_dbg(&master->dev, "DMA channel teardown\n");
+
+ if (sspi->tx_buf)
+ dmaengine_terminate_sync(master->dma_tx);
+ if (sspi->rx_buf)
+ dmaengine_terminate_sync(master->dma_rx);
+ }
+
+ sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
+
+ return ret;
+}
+
+static int sun4i_spi_transfer_one_pio(struct spi_device *spi,
+ struct spi_transfer *tfr)
+{
+ struct spi_master *master = spi->master;
+ struct sun4i_spi *sspi = spi_master_get_devdata(master);
+ int ret;
+
+ /* Explicit disable DMA requests */
+ sun4i_spi_write(sspi, SUN4I_DMA_CTL_REG, 0);
+ sun4i_spi_unset(sspi, SUN4I_CTL_REG, SUN4I_CTL_DMA_DEDICATED);
+
+ /* Fill the TX FIFO */
+ sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
+
+ /* Enable the interrupts */
+ sun4i_spi_set(sspi, SUN4I_INT_CTL_REG, SUN4I_INT_CTL_TC |
+ SUN4I_INT_CTL_RF_F34);
+
+ /* Start transfer */
+ sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_XCH);
+
+ ret = sun4i_spi_wait_for_transfer(spi, tfr);
+
+ sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
+
+ return ret;
+}
+
static int sun4i_spi_transfer_one(struct spi_master *master,
struct spi_device *spi,
struct spi_transfer *tfr)
@@ -242,13 +417,22 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
struct sun4i_spi *sspi = spi_master_get_devdata(master);
unsigned int mclk_rate, div;
unsigned int tx_len = 0;
- int ret = 0;
u32 reg;

- /* We don't support transfers larger than FIFO depth */
- if (tfr->len > SUN4I_FIFO_DEPTH)
+ /* A zero length transfer never finishes if programmed
+ in the hardware */
+ if (!tfr->len)
+ return 0;
+
+ if (tfr->len > SUN4I_MAX_XFER_SIZE)
return -EMSGSIZE;

+ if (!master->can_dma) {
+ /* Don't support transfer larger than the FIFO */
+ if (tfr->len > SUN4I_FIFO_DEPTH)
+ return -EMSGSIZE;
+ }
+
sspi->tx_buf = tfr->tx_buf;
sspi->rx_buf = tfr->rx_buf;
sspi->len = tfr->len;
@@ -335,23 +519,10 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
sun4i_spi_write(sspi, SUN4I_BURST_CNT_REG, SUN4I_BURST_CNT(tfr->len));
sun4i_spi_write(sspi, SUN4I_XMIT_CNT_REG, SUN4I_XMIT_CNT(tx_len));

- /*
- * Fill the TX FIFO
- */
- sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
-
- /* Enable the interrupts */
- sun4i_spi_set(sspi, SUN4I_INT_CTL_REG, SUN4I_INT_CTL_TC |
- SUN4I_INT_CTL_RF_F34);
-
- /* Start the transfer */
- sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_XCH);
-
- ret = sun4i_spi_wait_for_transfer(spi, tfr);
-
- sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
+ if (sun4i_spi_can_dma(master, spi, tfr))
+ return sun4i_spi_transfer_one_dma(spi, tfr);

- return ret;
+ return sun4i_spi_transfer_one_pio(spi, tfr);
}

static irqreturn_t sun4i_spi_handler(int irq, void *dev_id)
@@ -364,8 +535,7 @@ static irqreturn_t sun4i_spi_handler(int irq, void *dev_id)

/* Transfer complete */
if (status & SUN4I_INT_CTL_TC) {
- sun4i_spi_write(sspi, SUN4I_INT_STA_REG,
- SUN4I_INT_CTL_TC);
+ sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_TC);
sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
spi_finalize_current_transfer(master);
return IRQ_HANDLED;
@@ -422,6 +592,76 @@ static int sun4i_spi_runtime_suspend(struct device *dev)
return 0;
}

+static int sun4i_spi_dma_setup(struct device *dev,
+ struct resource *res)
+{
+ struct spi_master *master = dev_get_drvdata(dev);
+ struct dma_slave_config dma_sconf;
+ int ret;
+
+ master->dma_tx = dma_request_slave_channel_reason(dev, "tx");
+ if (IS_ERR(master->dma_tx)) {
+ dev_err(dev, "Unable to acquire DMA TX channel\n");
+ ret = PTR_ERR(master->dma_tx);
+ goto out;
+ }
+
+ dma_sconf.direction = DMA_MEM_TO_DEV;
+ dma_sconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ dma_sconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ dma_sconf.dst_addr = res->start + SUN4I_TXDATA_REG;
+ dma_sconf.dst_maxburst = 1;
+ dma_sconf.src_maxburst = 1;
+
+ ret = dmaengine_slave_config(master->dma_tx, &dma_sconf);
+ if (ret) {
+ dev_err(dev, "Unable to configure DMA TX slave\n");
+ goto err_rel_tx;
+ }
+
+ master->dma_rx = dma_request_slave_channel_reason(dev, "rx");
+ if (IS_ERR(master->dma_rx)) {
+ dev_err(dev, "Unable to acquire DMA RX channel\n");
+ ret = PTR_ERR(master->dma_rx);
+ goto err_rel_tx;
+ }
+
+ dma_sconf.direction = DMA_DEV_TO_MEM;
+ dma_sconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ dma_sconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ dma_sconf.src_addr = res->start + SUN4I_RXDATA_REG;
+ dma_sconf.src_maxburst = 1;
+ dma_sconf.dst_maxburst = 1;
+
+ ret = dmaengine_slave_config(master->dma_rx, &dma_sconf);
+ if (ret) {
+ dev_err(dev, "Unable to configure DMA RX slave\n");
+ goto err_rel_rx;
+ }
+
+ /* don't set can_dma unless both channels are valid*/
+ master->can_dma = sun4i_spi_can_dma;
+
+ return 0;
+
+err_rel_rx:
+ dma_release_channel(master->dma_rx);
+err_rel_tx:
+ dma_release_channel(master->dma_tx);
+out:
+ master->dma_tx = NULL;
+ master->dma_rx = NULL;
+ return ret;
+}
+
+static void sun4i_spi_dma_release(struct spi_master *master)
+{
+ if (master->can_dma) {
+ dma_release_channel(master->dma_rx);
+ dma_release_channel(master->dma_tx);
+ }
+}
+
static int sun4i_spi_probe(struct platform_device *pdev)
{
struct spi_master *master;
@@ -484,6 +724,16 @@ static int sun4i_spi_probe(struct platform_device *pdev)
goto err_free_master;
}

+ ret = sun4i_spi_dma_setup(&pdev->dev, res);
+ if (ret) {
+ if (ret == -EPROBE_DEFER) {
+ /* wait for the dma driver to load */
+ goto err_free_master;
+ }
+ dev_warn(&pdev->dev,
+ "Unable to setup DMA channels: DMA transfers disabled\n");
+ }
+
/*
* This wake-up/shutdown pattern is to be able to have the
* device woken up, even if runtime_pm is disabled
@@ -500,7 +750,7 @@ static int sun4i_spi_probe(struct platform_device *pdev)

ret = devm_spi_register_master(&pdev->dev, master);
if (ret) {
- dev_err(&pdev->dev, "cannot register SPI master\n");
+ dev_err(&pdev->dev, "Couldn't register SPI master\n");
goto err_pm_disable;
}

@@ -510,14 +760,19 @@ err_pm_disable:
pm_runtime_disable(&pdev->dev);
sun4i_spi_runtime_suspend(&pdev->dev);
err_free_master:
+ sun4i_spi_dma_release(master);
spi_master_put(master);
return ret;
}

static int sun4i_spi_remove(struct platform_device *pdev)
{
+ struct spi_master *master = platform_get_drvdata(pdev);
+
pm_runtime_force_suspend(&pdev->dev);

+ sun4i_spi_dma_release(master);
+
return 0;
}

--
2.16.2
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