[PATCH v6] spi: spi-imx: add DMA support

From: Robin Gong
Date: Mon Oct 20 2014 - 22:12:15 EST

Enable DMA support on i.mx6. The read speed can increase from 600KB/s
to 1.2MB/s on i.mx6q. You can disable or enable dma function in dts.
If not set "dma-names" in dts, spi will use PIO mode. This patch only
validate on i.mx6, not i.mx5, but encourage ones to apply this patch
on i.mx5 since they share the same IP.

Note:
Sometime, there is a weid data in rxfifo after one full tx/rx
transfer finish by DMA on i.mx6dl, so we disable dma functhion on
i.mx6dl.

Signed-off-by: Frank Li <Frank.Li@xxxxxxxxxxxxx>
Signed-off-by: Robin Gong <b38343@xxxxxxxxxxxxx>

---
Change from v5:
1. Update binding doc fsl-imx-cspi.txt.
2. remove usedma flag set from can_dma interface.

Change from v4:
1. Enrich comments.
2. Remove the rxfifo workaround. The issue only exist on i.mx6dl, so disable
dma function in dts.

Change from v3:
1. Use spi core framwork to handle dump tx/rx buf
2. Add one workaround for weird data in rxfifo when one full transfer done.

Change from v2:
http://thread.gmane.org/gmane.linux.ports.arm.kernel/291722/focus=294363
1. Dma setup only for imx51-ecspi
2. Use one small dummy buffer(1 bd size) to templiy store data
for meanless rx/tx, instead of malloc the actual transfer size.
3. Split spi_mx_sdma_transfer to smaller and easily to read.
4. Fix some code indent.
---
.../devicetree/bindings/spi/fsl-imx-cspi.txt | 5 +
drivers/spi/spi-imx.c | 286 ++++++++++++++++++++-
2 files changed, 285 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt b/Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt
index 4256a6d..aad527b 100644
--- a/Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt
+++ b/Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt
@@ -7,6 +7,9 @@ Required properties:
- interrupts : Should contain CSPI/eCSPI interrupt
- fsl,spi-num-chipselects : Contains the number of the chipselect
- cs-gpios : Specifies the gpio pins to be used for chipselects.
+- dmas: DMA specifiers for tx and rx dma. See the DMA client binding,
+ Documentation/devicetree/bindings/dma/dma.txt
+- dma-names: DMA request names should include "tx" and "rx" if present.

Example:

@@ -19,4 +22,6 @@ ecspi@70010000 {
fsl,spi-num-chipselects = <2>;
cs-gpios = <&gpio3 24 0>, /* GPIO3_24 */
<&gpio3 25 0>; /* GPIO3_25 */
+ dmas = <&sdma 3 7 1>, <&sdma 4 7 2>;
+ dma-names = "rx", "tx";
};
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 5daff20..3637847 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -21,6 +21,8 @@
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/delay.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/gpio.h>
#include <linux/interrupt.h>
@@ -37,6 +39,7 @@
#include <linux/of_device.h>
#include <linux/of_gpio.h>

+#include <linux/platform_data/dma-imx.h>
#include <linux/platform_data/spi-imx.h>

#define DRIVER_NAME "spi_imx"
@@ -51,6 +54,9 @@
#define MXC_INT_RR (1 << 0) /* Receive data ready interrupt */
#define MXC_INT_TE (1 << 1) /* Transmit FIFO empty interrupt */

+/* The maximum bytes that a sdma BD can transfer.*/
+#define MAX_SDMA_BD_BYTES (1 << 15)
+#define IMX_DMA_TIMEOUT (msecs_to_jiffies(3000))
struct spi_imx_config {
unsigned int speed_hz;
unsigned int bpw;
@@ -95,6 +101,16 @@ struct spi_imx_data {
const void *tx_buf;
unsigned int txfifo; /* number of words pushed in tx FIFO */

+ /* DMA */
+ unsigned int dma_is_inited;
+ unsigned int dma_finished;
+ bool usedma;
+ u32 rx_wml;
+ u32 tx_wml;
+ u32 rxt_wml;
+ struct completion dma_rx_completion;
+ struct completion dma_tx_completion;
+
const struct spi_imx_devtype_data *devtype_data;
int chipselect[0];
};
@@ -181,9 +197,21 @@ static unsigned int spi_imx_clkdiv_2(unsigned int fin,
return 7;
}

+static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
+ struct spi_transfer *transfer)
+{
+ struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
+
+ if (spi_imx->dma_is_inited && (transfer->len > spi_imx->rx_wml)
+ && (transfer->len > spi_imx->tx_wml))
+ return true;
+ return false;
+}
+
#define MX51_ECSPI_CTRL 0x08
#define MX51_ECSPI_CTRL_ENABLE (1 << 0)
#define MX51_ECSPI_CTRL_XCH (1 << 2)
+#define MX51_ECSPI_CTRL_SMC (1 << 3)
#define MX51_ECSPI_CTRL_MODE_MASK (0xf << 4)
#define MX51_ECSPI_CTRL_POSTDIV_OFFSET 8
#define MX51_ECSPI_CTRL_PREDIV_OFFSET 12
@@ -201,6 +229,18 @@ static unsigned int spi_imx_clkdiv_2(unsigned int fin,
#define MX51_ECSPI_INT_TEEN (1 << 0)
#define MX51_ECSPI_INT_RREN (1 << 3)

+#define MX51_ECSPI_DMA 0x14
+#define MX51_ECSPI_DMA_TX_WML_OFFSET 0
+#define MX51_ECSPI_DMA_TX_WML_MASK 0x3F
+#define MX51_ECSPI_DMA_RX_WML_OFFSET 16
+#define MX51_ECSPI_DMA_RX_WML_MASK (0x3F << 16)
+#define MX51_ECSPI_DMA_RXT_WML_OFFSET 24
+#define MX51_ECSPI_DMA_RXT_WML_MASK (0x3F << 24)
+
+#define MX51_ECSPI_DMA_TEDEN_OFFSET 7
+#define MX51_ECSPI_DMA_RXDEN_OFFSET 23
+#define MX51_ECSPI_DMA_RXTDEN_OFFSET 31
+
#define MX51_ECSPI_STAT 0x18
#define MX51_ECSPI_STAT_RR (1 << 3)

@@ -257,17 +297,22 @@ static void __maybe_unused mx51_ecspi_intctrl(struct spi_imx_data *spi_imx, int

static void __maybe_unused mx51_ecspi_trigger(struct spi_imx_data *spi_imx)
{
- u32 reg;
-
- reg = readl(spi_imx->base + MX51_ECSPI_CTRL);
- reg |= MX51_ECSPI_CTRL_XCH;
+ u32 reg = readl(spi_imx->base + MX51_ECSPI_CTRL);
+
+ if (!spi_imx->usedma)
+ reg |= MX51_ECSPI_CTRL_XCH;
+ else if (!spi_imx->dma_finished)
+ reg |= MX51_ECSPI_CTRL_SMC;
+ else
+ reg &= ~MX51_ECSPI_CTRL_SMC;
writel(reg, spi_imx->base + MX51_ECSPI_CTRL);
}

static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
struct spi_imx_config *config)
{
- u32 ctrl = MX51_ECSPI_CTRL_ENABLE, cfg = 0;
+ u32 ctrl = MX51_ECSPI_CTRL_ENABLE, cfg = 0, dma = 0;
+ u32 tx_wml_cfg, rx_wml_cfg, rxt_wml_cfg;
u32 clk = config->speed_hz, delay;

/*
@@ -319,6 +364,30 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
else /* SCLK is _very_ slow */
usleep_range(delay, delay + 10);

+ /*
+ * Configure the DMA register: setup the watermark
+ * and enable DMA request.
+ */
+ if (spi_imx->dma_is_inited) {
+ dma = readl(spi_imx->base + MX51_ECSPI_DMA);
+
+ spi_imx->tx_wml = spi_imx_get_fifosize(spi_imx) / 2;
+ spi_imx->rx_wml = spi_imx_get_fifosize(spi_imx) / 2;
+ spi_imx->rxt_wml = spi_imx_get_fifosize(spi_imx) / 2;
+ rx_wml_cfg = spi_imx->rx_wml << MX51_ECSPI_DMA_RX_WML_OFFSET;
+ tx_wml_cfg = spi_imx->tx_wml << MX51_ECSPI_DMA_TX_WML_OFFSET;
+ rxt_wml_cfg = spi_imx->rxt_wml << MX51_ECSPI_DMA_RXT_WML_OFFSET;
+ dma = (dma & ~MX51_ECSPI_DMA_TX_WML_MASK
+ & ~MX51_ECSPI_DMA_RX_WML_MASK
+ & ~MX51_ECSPI_DMA_RXT_WML_MASK)
+ | rx_wml_cfg | tx_wml_cfg | rxt_wml_cfg
+ |(1 << MX51_ECSPI_DMA_TEDEN_OFFSET)
+ |(1 << MX51_ECSPI_DMA_RXDEN_OFFSET)
+ |(1 << MX51_ECSPI_DMA_RXTDEN_OFFSET);
+
+ writel(dma, spi_imx->base + MX51_ECSPI_DMA);
+ }
+
return 0;
}

@@ -730,7 +799,186 @@ static int spi_imx_setupxfer(struct spi_device *spi,
return 0;
}

-static int spi_imx_transfer(struct spi_device *spi,
+static void spi_imx_sdma_exit(struct spi_imx_data *spi_imx)
+{
+ struct spi_master *master = spi_imx->bitbang.master;
+
+ if (master->dma_rx) {
+ dma_release_channel(master->dma_rx);
+ master->dma_rx = NULL;
+ }
+
+ if (master->dma_tx) {
+ dma_release_channel(master->dma_tx);
+ master->dma_tx = NULL;
+ }
+
+ spi_imx->dma_is_inited = 0;
+}
+
+static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
+ struct spi_master *master,
+ const struct resource *res)
+{
+ struct dma_slave_config slave_config = {};
+ int ret;
+
+ /* Prepare for TX DMA: */
+ master->dma_tx = dma_request_slave_channel(dev, "tx");
+ if (!master->dma_tx) {
+ dev_err(dev, "cannot get the TX DMA channel!\n");
+ ret = -EINVAL;
+ goto err;
+ }
+
+ slave_config.direction = DMA_MEM_TO_DEV;
+ slave_config.dst_addr = res->start + MXC_CSPITXDATA;
+ slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.dst_maxburst = spi_imx_get_fifosize(spi_imx) / 2;
+ ret = dmaengine_slave_config(master->dma_tx, &slave_config);
+ if (ret) {
+ dev_err(dev, "error in TX dma configuration.\n");
+ goto err;
+ }
+
+ /* Prepare for RX : */
+ master->dma_rx = dma_request_slave_channel(dev, "rx");
+ if (!master->dma_rx) {
+ dev_dbg(dev, "cannot get the DMA channel.\n");
+ ret = -EINVAL;
+ goto err;
+ }
+
+ slave_config.direction = DMA_DEV_TO_MEM;
+ slave_config.src_addr = res->start + MXC_CSPIRXDATA;
+ slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.src_maxburst = spi_imx_get_fifosize(spi_imx) / 2;
+ ret = dmaengine_slave_config(master->dma_rx, &slave_config);
+ if (ret) {
+ dev_err(dev, "error in RX dma configuration.\n");
+ goto err;
+ }
+
+ init_completion(&spi_imx->dma_rx_completion);
+ init_completion(&spi_imx->dma_tx_completion);
+ master->can_dma = spi_imx_can_dma;
+ master->max_dma_len = MAX_SDMA_BD_BYTES;
+ spi_imx->bitbang.master->flags = SPI_MASTER_MUST_RX |
+ SPI_MASTER_MUST_TX;
+ spi_imx->dma_is_inited = 1;
+
+ return 0;
+err:
+ spi_imx_sdma_exit(spi_imx);
+ return ret;
+}
+
+static void spi_imx_dma_rx_callback(void *cookie)
+{
+ struct spi_imx_data *spi_imx = (struct spi_imx_data *)cookie;
+
+ complete(&spi_imx->dma_rx_completion);
+}
+
+static void spi_imx_dma_tx_callback(void *cookie)
+{
+ struct spi_imx_data *spi_imx = (struct spi_imx_data *)cookie;
+
+ complete(&spi_imx->dma_tx_completion);
+}
+
+static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
+ struct spi_transfer *transfer)
+{
+ struct dma_async_tx_descriptor *desc_tx = NULL, *desc_rx = NULL;
+ int ret;
+ u32 dma;
+ int left;
+ struct spi_master *master = spi_imx->bitbang.master;
+ struct sg_table *tx = &transfer->tx_sg, *rx = &transfer->rx_sg;
+
+ if (tx) {
+ desc_tx = dmaengine_prep_slave_sg(master->dma_tx,
+ tx->sgl, tx->nents, DMA_TO_DEVICE,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ if (!desc_tx)
+ goto no_dma;
+
+ desc_tx->callback = spi_imx_dma_tx_callback;
+ desc_tx->callback_param = (void *)spi_imx;
+ dmaengine_submit(desc_tx);
+ }
+
+ if (rx) {
+ desc_rx = dmaengine_prep_slave_sg(master->dma_rx,
+ rx->sgl, rx->nents, DMA_FROM_DEVICE,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ if (!desc_rx)
+ goto no_dma;
+
+ desc_rx->callback = spi_imx_dma_rx_callback;
+ desc_rx->callback_param = (void *)spi_imx;
+ dmaengine_submit(desc_rx);
+ }
+
+ reinit_completion(&spi_imx->dma_rx_completion);
+ reinit_completion(&spi_imx->dma_tx_completion);
+
+ /* Trigger the cspi module. */
+ spi_imx->dma_finished = 0;
+
+ dma = readl(spi_imx->base + MX51_ECSPI_DMA);
+ dma = dma & (~MX51_ECSPI_DMA_RXT_WML_MASK);
+ /* Change RX_DMA_LENGTH trigger dma fetch tail data */
+ left = transfer->len % spi_imx->rxt_wml;
+ if (left)
+ writel(dma | (left << MX51_ECSPI_DMA_RXT_WML_OFFSET),
+ spi_imx->base + MX51_ECSPI_DMA);
+ spi_imx->devtype_data->trigger(spi_imx);
+
+ dma_async_issue_pending(master->dma_tx);
+ dma_async_issue_pending(master->dma_rx);
+ /* Wait SDMA to finish the data transfer.*/
+ ret = wait_for_completion_timeout(&spi_imx->dma_tx_completion,
+ IMX_DMA_TIMEOUT);
+ if (!ret) {
+ pr_warn("%s %s: I/O Error in DMA TX\n",
+ dev_driver_string(&master->dev),
+ dev_name(&master->dev));
+ dmaengine_terminate_all(master->dma_tx);
+ } else {
+ ret = wait_for_completion_timeout(&spi_imx->dma_rx_completion,
+ IMX_DMA_TIMEOUT);
+ if (!ret) {
+ pr_warn("%s %s: I/O Error in DMA RX\n",
+ dev_driver_string(&master->dev),
+ dev_name(&master->dev));
+ spi_imx->devtype_data->reset(spi_imx);
+ dmaengine_terminate_all(master->dma_rx);
+ }
+ writel(dma |
+ spi_imx->rxt_wml << MX51_ECSPI_DMA_RXT_WML_OFFSET,
+ spi_imx->base + MX51_ECSPI_DMA);
+ }
+
+ spi_imx->dma_finished = 1;
+ spi_imx->devtype_data->trigger(spi_imx);
+
+ if (!ret)
+ ret = -ETIMEDOUT;
+ else if (ret > 0)
+ ret = transfer->len;
+
+ return ret;
+
+no_dma:
+ pr_warn_once("%s %s: DMA not available, falling back to PIO\n",
+ dev_driver_string(&master->dev),
+ dev_name(&master->dev));
+ return -EAGAIN;
+}
+
+static int spi_imx_pio_transfer(struct spi_device *spi,
struct spi_transfer *transfer)
{
struct spi_imx_data *spi_imx = spi_master_get_devdata(spi->master);
@@ -751,6 +999,24 @@ static int spi_imx_transfer(struct spi_device *spi,
return transfer->len;
}

+static int spi_imx_transfer(struct spi_device *spi,
+ struct spi_transfer *transfer)
+{
+ int ret;
+ struct spi_imx_data *spi_imx = spi_master_get_devdata(spi->master);
+
+ if (spi_imx->bitbang.master->can_dma &&
+ spi_imx_can_dma(spi_imx->bitbang.master, spi, transfer)) {
+ spi_imx->usedma = true;
+ ret = spi_imx_dma_transfer(spi_imx, transfer);
+ if (ret != -EAGAIN)
+ return ret;
+ }
+ spi_imx->usedma = false;
+
+ return spi_imx_pio_transfer(spi, transfer);
+}
+
static int spi_imx_setup(struct spi_device *spi)
{
struct spi_imx_data *spi_imx = spi_master_get_devdata(spi->master);
@@ -911,6 +1177,13 @@ static int spi_imx_probe(struct platform_device *pdev)
goto out_put_per;

spi_imx->spi_clk = clk_get_rate(spi_imx->clk_per);
+ /*
+ * Only validated on i.mx6 now, can remove the constrain if validated on
+ * other chips.
+ */
+ if (spi_imx->devtype_data == &imx51_ecspi_devtype_data
+ && spi_imx_sdma_init(&pdev->dev, spi_imx, master, res))
+ dev_err(&pdev->dev, "dma setup error,use pio instead\n");

spi_imx->devtype_data->reset(spi_imx);

@@ -949,6 +1222,7 @@ static int spi_imx_remove(struct platform_device *pdev)
writel(0, spi_imx->base + MXC_CSPICTRL);
clk_unprepare(spi_imx->clk_ipg);
clk_unprepare(spi_imx->clk_per);
+ spi_imx_sdma_exit(spi_imx);
spi_master_put(master);

return 0;
--
1.9.1

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