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Subject[PATCH 5/5] spi/ep93xx: add DMA support
Date
This patch adds DMA support for the EP93xx SPI driver. By default the DMA is
not enabled but it can be enabled by setting ep93xx_spi_info.use_dma to true
in board configuration file.

Note that the SPI driver still uses PIO for small transfers (<= 8 bytes) for
performance reasons.

Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
Cc: Grant Likely <grant.likely@secretlab.ca>
---
Documentation/spi/ep93xx_spi | 10 +
arch/arm/mach-ep93xx/core.c | 6 +-
arch/arm/mach-ep93xx/include/mach/ep93xx_spi.h | 2 +
drivers/spi/ep93xx_spi.c | 303 +++++++++++++++++++++++-
4 files changed, 308 insertions(+), 13 deletions(-)
diff --git a/Documentation/spi/ep93xx_spi b/Documentation/spi/ep93xx_spi
index 6325f5b..fc43818 100644
--- a/Documentation/spi/ep93xx_spi
+++ b/Documentation/spi/ep93xx_spi
@@ -88,6 +88,16 @@ static void __init ts72xx_init_machine(void)
ARRAY_SIZE(ts72xx_spi_devices));
}

+The driver can use DMA for the transfers also. In this case ts72xx_spi_info
+becomes:
+
+static struct ep93xx_spi_info ts72xx_spi_info = {
+ .num_chipselect = ARRAY_SIZE(ts72xx_spi_devices),
+ .use_dma = true;
+};
+
+Note that CONFIG_DMA_ENGINE and CONFIG_EP93XX_DMA should be enabled as well.
+
Thanks to
=========
Martin Guy, H. Hartley Sweeten and others who helped me during development of
diff --git a/arch/arm/mach-ep93xx/core.c b/arch/arm/mach-ep93xx/core.c
index 8207954..cc9f1d4 100644
--- a/arch/arm/mach-ep93xx/core.c
+++ b/arch/arm/mach-ep93xx/core.c
@@ -488,11 +488,15 @@ static struct resource ep93xx_spi_resources[] = {
},
};

+static u64 ep93xx_spi_dma_mask = DMA_BIT_MASK(32);
+
static struct platform_device ep93xx_spi_device = {
.name = "ep93xx-spi",
.id = 0,
.dev = {
- .platform_data = &ep93xx_spi_master_data,
+ .platform_data = &ep93xx_spi_master_data,
+ .coherent_dma_mask = DMA_BIT_MASK(32),
+ .dma_mask = &ep93xx_spi_dma_mask,
},
.num_resources = ARRAY_SIZE(ep93xx_spi_resources),
.resource = ep93xx_spi_resources,
diff --git a/arch/arm/mach-ep93xx/include/mach/ep93xx_spi.h b/arch/arm/mach-ep93xx/include/mach/ep93xx_spi.h
index 0a37961..9bb63ac 100644
--- a/arch/arm/mach-ep93xx/include/mach/ep93xx_spi.h
+++ b/arch/arm/mach-ep93xx/include/mach/ep93xx_spi.h
@@ -7,9 +7,11 @@ struct spi_device;
* struct ep93xx_spi_info - EP93xx specific SPI descriptor
* @num_chipselect: number of chip selects on this board, must be
* at least one
+ * @use_dma: use DMA for the transfers
*/
struct ep93xx_spi_info {
int num_chipselect;
+ bool use_dma;
};

/**
diff --git a/drivers/spi/ep93xx_spi.c b/drivers/spi/ep93xx_spi.c
index d357007..1cf6454 100644
--- a/drivers/spi/ep93xx_spi.c
+++ b/drivers/spi/ep93xx_spi.c
@@ -1,7 +1,7 @@
/*
* Driver for Cirrus Logic EP93xx SPI controller.
*
- * Copyright (c) 2010 Mika Westerberg
+ * Copyright (C) 2010-2011 Mika Westerberg
*
* Explicit FIFO handling code was inspired by amba-pl022 driver.
*
@@ -21,13 +21,16 @@
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/device.h>
+#include <linux/dmaengine.h>
#include <linux/bitops.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/workqueue.h>
#include <linux/sched.h>
+#include <linux/scatterlist.h>
#include <linux/spi/spi.h>

+#include <mach/dma.h>
#include <mach/ep93xx_spi.h>

#define SSPCR0 0x0000
@@ -71,6 +74,7 @@
* @pdev: pointer to platform device
* @clk: clock for the controller
* @regs_base: pointer to ioremap()'d registers
+ * @sspdr_phys: physical address of the SSPDR register
* @irq: IRQ number used by the driver
* @min_rate: minimum clock rate (in Hz) supported by the controller
* @max_rate: maximum clock rate (in Hz) supported by the controller
@@ -84,6 +88,14 @@
* @rx: current byte in transfer to receive
* @fifo_level: how full is FIFO (%0..%SPI_FIFO_SIZE - %1). Receiving one
* frame decreases this level and sending one frame increases it.
+ * @dma_rx: RX DMA channel
+ * @dma_tx: TX DMA channel
+ * @dma_rx_data: RX parameters passed to the DMA engine
+ * @dma_tx_data: TX parameters passed to the DMA engine
+ * @rx_sgt: sg table for RX transfers
+ * @tx_sgt: sg table for TX transfers
+ * @zeropage: dummy page used as RX buffer when only TX buffer is passed in by
+ * the client
*
* This structure holds EP93xx SPI controller specific information. When
* @running is %true, driver accepts transfer requests from protocol drivers.
@@ -100,6 +112,7 @@ struct ep93xx_spi {
const struct platform_device *pdev;
struct clk *clk;
void __iomem *regs_base;
+ unsigned long sspdr_phys;
int irq;
unsigned long min_rate;
unsigned long max_rate;
@@ -112,6 +125,13 @@ struct ep93xx_spi {
size_t tx;
size_t rx;
size_t fifo_level;
+ struct dma_chan *dma_rx;
+ struct dma_chan *dma_tx;
+ struct ep93xx_dma_data dma_rx_data;
+ struct ep93xx_dma_data dma_tx_data;
+ struct sg_table rx_sgt;
+ struct sg_table tx_sgt;
+ void *zeropage;
};

/**
@@ -496,14 +516,195 @@ static int ep93xx_spi_read_write(struct ep93xx_spi *espi)
espi->fifo_level++;
}

- if (espi->rx == t->len) {
- msg->actual_length += t->len;
+ if (espi->rx == t->len)
return 0;
- }

return -EINPROGRESS;
}

+static void ep93xx_spi_pio_transfer(struct ep93xx_spi *espi)
+{
+ /*
+ * Now everything is set up for the current transfer. We prime the TX
+ * FIFO, enable interrupts, and wait for the transfer to complete.
+ */
+ if (ep93xx_spi_read_write(espi)) {
+ ep93xx_spi_enable_interrupts(espi);
+ wait_for_completion(&espi->wait);
+ }
+}
+
+/**
+ * ep93xx_spi_dma_prepare() - prepares a DMA transfer
+ * @espi: ep93xx SPI controller struct
+ * @dir: DMA transfer direction
+ *
+ * Function configures the DMA, maps the buffer and prepares the DMA
+ * descriptor. Returns a valid DMA descriptor in case of success and ERR_PTR
+ * in case of failure.
+ */
+static struct dma_async_tx_descriptor *
+ep93xx_spi_dma_prepare(struct ep93xx_spi *espi, enum dma_data_direction dir)
+{
+ struct spi_transfer *t = espi->current_msg->state;
+ struct dma_async_tx_descriptor *txd;
+ enum dma_slave_buswidth buswidth;
+ struct dma_slave_config conf;
+ struct scatterlist *sg;
+ struct sg_table *sgt;
+ struct dma_chan *chan;
+ const void *buf, *pbuf;
+ size_t len = t->len;
+ int i, ret, nents;
+
+ if (bits_per_word(espi) > 8)
+ buswidth = DMA_SLAVE_BUSWIDTH_2_BYTES;
+ else
+ buswidth = DMA_SLAVE_BUSWIDTH_1_BYTE;
+
+ memset(&conf, 0, sizeof(conf));
+ conf.direction = dir;
+
+ if (dir == DMA_FROM_DEVICE) {
+ chan = espi->dma_rx;
+ buf = t->rx_buf;
+ sgt = &espi->rx_sgt;
+
+ conf.src_addr = espi->sspdr_phys;
+ conf.src_addr_width = buswidth;
+ } else {
+ chan = espi->dma_tx;
+ buf = t->tx_buf;
+ sgt = &espi->tx_sgt;
+
+ conf.dst_addr = espi->sspdr_phys;
+ conf.dst_addr_width = buswidth;
+ }
+
+ ret = dmaengine_slave_config(chan, &conf);
+ if (ret)
+ return ERR_PTR(ret);
+
+ /*
+ * We need to split the transfer into PAGE_SIZE'd chunks. This is
+ * because we are using @espi->zeropage to provide a zero RX buffer
+ * for the TX transfers and we have only allocated one page for that.
+ *
+ * For performance reasons we allocate a new sg_table only when
+ * needed. Otherwise we will re-use the current one. Eventually the
+ * last sg_table is released in ep93xx_spi_release_dma().
+ */
+
+ nents = DIV_ROUND_UP(len, PAGE_SIZE);
+ if (nents != sgt->nents) {
+ sg_free_table(sgt);
+
+ ret = sg_alloc_table(sgt, nents, GFP_KERNEL);
+ if (ret)
+ return ERR_PTR(ret);
+ }
+
+ pbuf = buf;
+ for_each_sg(sgt->sgl, sg, sgt->nents, i) {
+ size_t bytes = min_t(size_t, len, PAGE_SIZE);
+
+ if (buf) {
+ sg_set_page(sg, virt_to_page(pbuf), bytes,
+ offset_in_page(pbuf));
+ } else {
+ sg_set_page(sg, virt_to_page(espi->zeropage),
+ bytes, 0);
+ }
+
+ pbuf += bytes;
+ len -= bytes;
+ }
+
+ if (WARN_ON(len)) {
+ dev_warn(&espi->pdev->dev, "len = %d expected 0!", len);
+ return ERR_PTR(-EINVAL);
+ }
+
+ nents = dma_map_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
+ if (!nents)
+ return ERR_PTR(-ENOMEM);
+
+ txd = chan->device->device_prep_slave_sg(chan, sgt->sgl, nents,
+ dir, DMA_CTRL_ACK);
+ if (!txd) {
+ dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
+ return ERR_PTR(-ENOMEM);
+ }
+ return txd;
+}
+
+/**
+ * ep93xx_spi_dma_finish() - finishes with a DMA transfer
+ * @espi: ep93xx SPI controller struct
+ * @dir: DMA transfer direction
+ *
+ * Function finishes with the DMA transfer. After this, the DMA buffer is
+ * unmapped.
+ */
+static void ep93xx_spi_dma_finish(struct ep93xx_spi *espi,
+ enum dma_data_direction dir)
+{
+ struct dma_chan *chan;
+ struct sg_table *sgt;
+
+ if (dir == DMA_FROM_DEVICE) {
+ chan = espi->dma_rx;
+ sgt = &espi->rx_sgt;
+ } else {
+ chan = espi->dma_tx;
+ sgt = &espi->tx_sgt;
+ }
+
+ dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
+}
+
+static void ep93xx_spi_dma_callback(void *callback_param)
+{
+ complete(callback_param);
+}
+
+static void ep93xx_spi_dma_transfer(struct ep93xx_spi *espi)
+{
+ struct spi_message *msg = espi->current_msg;
+ struct dma_async_tx_descriptor *rxd, *txd;
+
+ rxd = ep93xx_spi_dma_prepare(espi, DMA_FROM_DEVICE);
+ if (IS_ERR(rxd)) {
+ dev_err(&espi->pdev->dev, "DMA RX failed: %ld\n", PTR_ERR(rxd));
+ msg->status = PTR_ERR(rxd);
+ return;
+ }
+
+ txd = ep93xx_spi_dma_prepare(espi, DMA_TO_DEVICE);
+ if (IS_ERR(txd)) {
+ ep93xx_spi_dma_finish(espi, DMA_FROM_DEVICE);
+ dev_err(&espi->pdev->dev, "DMA TX failed: %ld\n", PTR_ERR(rxd));
+ msg->status = PTR_ERR(txd);
+ return;
+ }
+
+ /* We are ready when RX is done */
+ rxd->callback = ep93xx_spi_dma_callback;
+ rxd->callback_param = &espi->wait;
+
+ /* Now submit both descriptors and wait while they finish */
+ dmaengine_submit(rxd);
+ dmaengine_submit(txd);
+
+ dma_async_issue_pending(espi->dma_rx);
+ dma_async_issue_pending(espi->dma_tx);
+
+ wait_for_completion(&espi->wait);
+
+ ep93xx_spi_dma_finish(espi, DMA_TO_DEVICE);
+ ep93xx_spi_dma_finish(espi, DMA_FROM_DEVICE);
+}
+
/**
* ep93xx_spi_process_transfer() - processes one SPI transfer
* @espi: ep93xx SPI controller struct
@@ -556,13 +757,14 @@ static void ep93xx_spi_process_transfer(struct ep93xx_spi *espi,
espi->tx = 0;

/*
- * Now everything is set up for the current transfer. We prime the TX
- * FIFO, enable interrupts, and wait for the transfer to complete.
+ * There is no point of setting up DMA for the transfers which will
+ * fit into the FIFO and can be transferred with a single interrupt.
+ * So in these cases we will be using PIO and don't bother for DMA.
*/
- if (ep93xx_spi_read_write(espi)) {
- ep93xx_spi_enable_interrupts(espi);
- wait_for_completion(&espi->wait);
- }
+ if (espi->dma_rx && t->len > SPI_FIFO_SIZE)
+ ep93xx_spi_dma_transfer(espi);
+ else
+ ep93xx_spi_pio_transfer(espi);

/*
* In case of error during transmit, we bail out from processing
@@ -571,6 +773,8 @@ static void ep93xx_spi_process_transfer(struct ep93xx_spi *espi,
if (msg->status)
return;

+ msg->actual_length += t->len;
+
/*
* After this transfer is finished, perform any possible
* post-transfer actions requested by the protocol driver.
@@ -752,6 +956,75 @@ static irqreturn_t ep93xx_spi_interrupt(int irq, void *dev_id)
return IRQ_HANDLED;
}

+static bool ep93xx_spi_dma_filter(struct dma_chan *chan, void *filter_param)
+{
+ if (ep93xx_dma_chan_is_m2p(chan))
+ return false;
+
+ chan->private = filter_param;
+ return true;
+}
+
+static int ep93xx_spi_setup_dma(struct ep93xx_spi *espi)
+{
+ dma_cap_mask_t mask;
+ int ret;
+
+ espi->zeropage = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!espi->zeropage)
+ return -ENOMEM;
+
+ dma_cap_zero(mask);
+ dma_cap_set(DMA_SLAVE, mask);
+
+ espi->dma_rx_data.port = EP93XX_DMA_SSP;
+ espi->dma_rx_data.direction = DMA_FROM_DEVICE;
+ espi->dma_rx_data.name = "ep93xx-spi-rx";
+
+ espi->dma_rx = dma_request_channel(mask, ep93xx_spi_dma_filter,
+ &espi->dma_rx_data);
+ if (!espi->dma_rx) {
+ ret = -ENODEV;
+ goto fail_free_page;
+ }
+
+ espi->dma_tx_data.port = EP93XX_DMA_SSP;
+ espi->dma_tx_data.direction = DMA_TO_DEVICE;
+ espi->dma_tx_data.name = "ep93xx-spi-tx";
+
+ espi->dma_tx = dma_request_channel(mask, ep93xx_spi_dma_filter,
+ &espi->dma_tx_data);
+ if (!espi->dma_tx) {
+ ret = -ENODEV;
+ goto fail_release_rx;
+ }
+
+ return 0;
+
+fail_release_rx:
+ dma_release_channel(espi->dma_rx);
+ espi->dma_rx = NULL;
+fail_free_page:
+ free_page((unsigned long)espi->zeropage);
+
+ return ret;
+}
+
+static void ep93xx_spi_release_dma(struct ep93xx_spi *espi)
+{
+ if (espi->dma_rx) {
+ dma_release_channel(espi->dma_rx);
+ sg_free_table(&espi->rx_sgt);
+ }
+ if (espi->dma_tx) {
+ dma_release_channel(espi->dma_tx);
+ sg_free_table(&espi->tx_sgt);
+ }
+
+ if (espi->zeropage)
+ free_page((unsigned long)espi->zeropage);
+}
+
static int __init ep93xx_spi_probe(struct platform_device *pdev)
{
struct spi_master *master;
@@ -818,6 +1091,7 @@ static int __init ep93xx_spi_probe(struct platform_device *pdev)
goto fail_put_clock;
}

+ espi->sspdr_phys = res->start + SSPDR;
espi->regs_base = ioremap(res->start, resource_size(res));
if (!espi->regs_base) {
dev_err(&pdev->dev, "failed to map resources\n");
@@ -832,10 +1106,13 @@ static int __init ep93xx_spi_probe(struct platform_device *pdev)
goto fail_unmap_regs;
}

+ if (info->use_dma && ep93xx_spi_setup_dma(espi))
+ dev_warn(&pdev->dev, "DMA setup failed. Falling back to PIO\n");
+
espi->wq = create_singlethread_workqueue("ep93xx_spid");
if (!espi->wq) {
dev_err(&pdev->dev, "unable to create workqueue\n");
- goto fail_free_irq;
+ goto fail_free_dma;
}
INIT_WORK(&espi->msg_work, ep93xx_spi_work);
INIT_LIST_HEAD(&espi->msg_queue);
@@ -857,7 +1134,8 @@ static int __init ep93xx_spi_probe(struct platform_device *pdev)

fail_free_queue:
destroy_workqueue(espi->wq);
-fail_free_irq:
+fail_free_dma:
+ ep93xx_spi_release_dma(espi);
free_irq(espi->irq, espi);
fail_unmap_regs:
iounmap(espi->regs_base);
@@ -901,6 +1179,7 @@ static int __exit ep93xx_spi_remove(struct platform_device *pdev)
}
spin_unlock_irq(&espi->lock);

+ ep93xx_spi_release_dma(espi);
free_irq(espi->irq, espi);
iounmap(espi->regs_base);
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
--
1.7.4.4


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