spi/bfin_spi: utilize the SPI interrupt in PIO mode

The current behavior in PIO mode is to poll the SPI status registers which
can obviously lead to higher latencies when doing a lot of SPI traffic.
There is a SPI interrupt which can be used instead to signal individual
completion of transactions.

Signed-off-by: Yi Li <yi.li@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 185 insertions, 50 deletions

diff --git a/drivers/spi/spi_bfin5xx.c b/drivers/spi/spi_bfin5xx.c
index b8352546c589..3736c3596a41 100644
--- a/drivers/spi/spi_bfin5xx.c
+++ b/drivers/spi/spi_bfin5xx.c
@@ -92,6 +92,9 @@ struct driver_data {
         dma_addr_t rx_dma;
         dma_addr_t tx_dma;
 
+        int irq_requested;
+        int spi_irq;
+
         size_t rx_map_len;
         size_t tx_map_len;
         u8 n_bytes;
@@ -115,6 +118,7 @@ struct chip_data {
         u16 cs_chg_udelay;      /* Some devices require > 255usec delay */
         u32 cs_gpio;
         u16 idle_tx_val;
+        u8 pio_interrupt;       /* use spi data irq */
         void (*write) (struct driver_data *);
         void (*read) (struct driver_data *);
         void (*duplex) (struct driver_data *);
@@ -525,6 +529,79 @@ static void bfin_spi_giveback(struct driver_data *drv_data)
                 msg->complete(msg->context);
 }
 
+/* spi data irq handler */
+static irqreturn_t bfin_spi_pio_irq_handler(int irq, void *dev_id)
+{
+        struct driver_data *drv_data = dev_id;
+        struct chip_data *chip = drv_data->cur_chip;
+        struct spi_message *msg = drv_data->cur_msg;
+        int n_bytes = drv_data->n_bytes;
+
+        /* wait until transfer finished. */
+        while (!(read_STAT(drv_data) & BIT_STAT_RXS))
+                cpu_relax();
+
+        if ((drv_data->tx && drv_data->tx >= drv_data->tx_end) ||
+                (drv_data->rx && drv_data->rx >= (drv_data->rx_end - n_bytes))) {
+                /* last read */
+                if (drv_data->rx) {
+                        dev_dbg(&drv_data->pdev->dev, "last read\n");
+                        if (n_bytes == 2)
+                                *(u16 *) (drv_data->rx) = read_RDBR(drv_data);
+                        else if (n_bytes == 1)
+                                *(u8 *) (drv_data->rx) = read_RDBR(drv_data);
+                        drv_data->rx += n_bytes;
+                }
+
+                msg->actual_length += drv_data->len_in_bytes;
+                if (drv_data->cs_change)
+                        bfin_spi_cs_deactive(drv_data, chip);
+                /* Move to next transfer */
+                msg->state = bfin_spi_next_transfer(drv_data);
+
+                disable_irq(drv_data->spi_irq);
+
+                /* Schedule transfer tasklet */
+                tasklet_schedule(&drv_data->pump_transfers);
+                return IRQ_HANDLED;
+        }
+
+        if (drv_data->rx && drv_data->tx) {
+                /* duplex */
+                dev_dbg(&drv_data->pdev->dev, "duplex: write_TDBR\n");
+                if (drv_data->n_bytes == 2) {
+                        *(u16 *) (drv_data->rx) = read_RDBR(drv_data);
+                        write_TDBR(drv_data, (*(u16 *) (drv_data->tx)));
+                } else if (drv_data->n_bytes == 1) {
+                        *(u8 *) (drv_data->rx) = read_RDBR(drv_data);
+                        write_TDBR(drv_data, (*(u8 *) (drv_data->tx)));
+                }
+        } else if (drv_data->rx) {
+                /* read */
+                dev_dbg(&drv_data->pdev->dev, "read: write_TDBR\n");
+                if (drv_data->n_bytes == 2)
+                        *(u16 *) (drv_data->rx) = read_RDBR(drv_data);
+                else if (drv_data->n_bytes == 1)
+                        *(u8 *) (drv_data->rx) = read_RDBR(drv_data);
+                write_TDBR(drv_data, chip->idle_tx_val);
+        } else if (drv_data->tx) {
+                /* write */
+                dev_dbg(&drv_data->pdev->dev, "write: write_TDBR\n");
+                bfin_spi_dummy_read(drv_data);
+                if (drv_data->n_bytes == 2)
+                        write_TDBR(drv_data, (*(u16 *) (drv_data->tx)));
+                else if (drv_data->n_bytes == 1)
+                        write_TDBR(drv_data, (*(u8 *) (drv_data->tx)));
+        }
+
+        if (drv_data->tx)
+                drv_data->tx += n_bytes;
+        if (drv_data->rx)
+                drv_data->rx += n_bytes;
+
+        return IRQ_HANDLED;
+}
+
 static irqreturn_t bfin_spi_dma_irq_handler(int irq, void *dev_id)
 {
         struct driver_data *drv_data = dev_id;
@@ -700,6 +777,7 @@ static void bfin_spi_pump_transfers(unsigned long data)
 
         default:
                 /* No change, the same as default setting */
+                transfer->bits_per_word = chip->bits_per_word;
                 drv_data->n_bytes = chip->n_bytes;
                 width = chip->width;
                 drv_data->write = drv_data->tx ? chip->write : bfin_spi_null_writer;
@@ -842,60 +920,86 @@ static void bfin_spi_pump_transfers(unsigned long data)
                 dma_enable_irq(drv_data->dma_channel);
                 local_irq_restore(flags);
 
-        } else {
-                /* IO mode write then read */
-                dev_dbg(&drv_data->pdev->dev, "doing IO transfer\n");
+                return;
+        }
 
-                /* we always use SPI_WRITE mode. SPI_READ mode
-                   seems to have problems with setting up the
-                   output value in TDBR prior to the transfer. */
+        if (chip->pio_interrupt) {
+                /* use write mode. spi irq should have been disabled */
+                cr = (read_CTRL(drv_data) & (~BIT_CTL_TIMOD));
                 write_CTRL(drv_data, (cr | CFG_SPI_WRITE));
 
-                if (full_duplex) {
-                        /* full duplex mode */
-                        BUG_ON((drv_data->tx_end - drv_data->tx) !=
-                               (drv_data->rx_end - drv_data->rx));
-                        dev_dbg(&drv_data->pdev->dev,
-                                "IO duplex: cr is 0x%x\n", cr);
-
-                        drv_data->duplex(drv_data);
-
-                        if (drv_data->tx != drv_data->tx_end)
-                                tranf_success = 0;
-                } else if (drv_data->tx != NULL) {
-                        /* write only half duplex */
-                        dev_dbg(&drv_data->pdev->dev,
-                                "IO write: cr is 0x%x\n", cr);
+                /* discard old RX data and clear RXS */
+                bfin_spi_dummy_read(drv_data);
 
-                        drv_data->write(drv_data);
+                /* start transfer */
+                if (drv_data->tx == NULL)
+                        write_TDBR(drv_data, chip->idle_tx_val);
+                else {
+                        if (transfer->bits_per_word == 8)
+                                write_TDBR(drv_data, (*(u8 *) (drv_data->tx)));
+                        else if (transfer->bits_per_word == 16)
+                                write_TDBR(drv_data, (*(u16 *) (drv_data->tx)));
+                        drv_data->tx += drv_data->n_bytes;
+                }
 
-                        if (drv_data->tx != drv_data->tx_end)
-                                tranf_success = 0;
-                } else if (drv_data->rx != NULL) {
-                        /* read only half duplex */
-                        dev_dbg(&drv_data->pdev->dev,
-                                "IO read: cr is 0x%x\n", cr);
+                /* once TDBR is empty, interrupt is triggered */
+                enable_irq(drv_data->spi_irq);
+                return;
+        }
 
-                        drv_data->read(drv_data);
-                        if (drv_data->rx != drv_data->rx_end)
-                                tranf_success = 0;
-                }
+        /* IO mode */
+        dev_dbg(&drv_data->pdev->dev, "doing IO transfer\n");
+
+        /* we always use SPI_WRITE mode. SPI_READ mode
+           seems to have problems with setting up the
+           output value in TDBR prior to the transfer. */
+        write_CTRL(drv_data, (cr | CFG_SPI_WRITE));
+
+        if (full_duplex) {
+                /* full duplex mode */
+                BUG_ON((drv_data->tx_end - drv_data->tx) !=
+                       (drv_data->rx_end - drv_data->rx));
+                dev_dbg(&drv_data->pdev->dev,
+                        "IO duplex: cr is 0x%x\n", cr);
+
+                drv_data->duplex(drv_data);
+
+                if (drv_data->tx != drv_data->tx_end)
+                        tranf_success = 0;
+        } else if (drv_data->tx != NULL) {
+                /* write only half duplex */
+                dev_dbg(&drv_data->pdev->dev,
+                        "IO write: cr is 0x%x\n", cr);
+
+                drv_data->write(drv_data);
+
+                if (drv_data->tx != drv_data->tx_end)
+                        tranf_success = 0;
+        } else if (drv_data->rx != NULL) {
+                /* read only half duplex */
+                dev_dbg(&drv_data->pdev->dev,
+                        "IO read: cr is 0x%x\n", cr);
+
+                drv_data->read(drv_data);
+                if (drv_data->rx != drv_data->rx_end)
+                        tranf_success = 0;
+        }
 
-                if (!tranf_success) {
-                        dev_dbg(&drv_data->pdev->dev,
-                                "IO write error!\n");
-                        message->state = ERROR_STATE;
-                } else {
-                        /* Update total byte transfered */
-                        message->actual_length += drv_data->len_in_bytes;
-                        /* Move to next transfer of this msg */
-                        message->state = bfin_spi_next_transfer(drv_data);
-                        if (drv_data->cs_change)
-                                bfin_spi_cs_deactive(drv_data, chip);
-                }
-                /* Schedule next transfer tasklet */
-                tasklet_schedule(&drv_data->pump_transfers);
+        if (!tranf_success) {
+                dev_dbg(&drv_data->pdev->dev,
+                        "IO write error!\n");
+                message->state = ERROR_STATE;
+        } else {
+                /* Update total byte transfered */
+                message->actual_length += drv_data->len_in_bytes;
+                /* Move to next transfer of this msg */
+                message->state = bfin_spi_next_transfer(drv_data);
+                if (drv_data->cs_change)
+                        bfin_spi_cs_deactive(drv_data, chip);
         }
+
+        /* Schedule next transfer tasklet */
+        tasklet_schedule(&drv_data->pump_transfers);
 }
 
 /* pop a msg from queue and kick off real transfer */
@@ -1047,6 +1151,7 @@ static int bfin_spi_setup(struct spi_device *spi)
                 chip->cs_chg_udelay = chip_info->cs_chg_udelay;
                 chip->cs_gpio = chip_info->cs_gpio;
                 chip->idle_tx_val = chip_info->idle_tx_val;
+                chip->pio_interrupt = chip_info->pio_interrupt;
         }
 
         /* translate common spi framework into our register */
@@ -1096,6 +1201,11 @@ static int bfin_spi_setup(struct spi_device *spi)
                 goto error;
         }
 
+        if (chip->enable_dma && chip->pio_interrupt) {
+                dev_err(&spi->dev, "enable_dma is set, "
+                                "do not set pio_interrupt\n");
+                goto error;
+        }
         /*
          * if any one SPI chip is registered and wants DMA, request the
          * DMA channel for it
@@ -1119,6 +1229,18 @@ static int bfin_spi_setup(struct spi_device *spi)
                 dma_disable_irq(drv_data->dma_channel);
         }
 
+        if (chip->pio_interrupt && !drv_data->irq_requested) {
+                ret = request_irq(drv_data->spi_irq, bfin_spi_pio_irq_handler,
+                        IRQF_DISABLED, "BFIN_SPI", drv_data);
+                if (ret) {
+                        dev_err(&spi->dev, "Unable to register spi IRQ\n");
+                        goto error;
+                }
+                drv_data->irq_requested = 1;
+                /* we use write mode, spi irq has to be disabled here */
+                disable_irq(drv_data->spi_irq);
+        }
+
         if (chip->chip_select_num == 0) {
                 ret = gpio_request(chip->cs_gpio, spi->modalias);
                 if (ret) {
@@ -1328,11 +1450,19 @@ static int __init bfin_spi_probe(struct platform_device *pdev)
                 goto out_error_ioremap;
         }
 
-        drv_data->dma_channel = platform_get_irq(pdev, 0);
-        if (drv_data->dma_channel < 0) {
+        res = platform_get_resource(pdev, IORESOURCE_DMA, 0);
+        if (res == NULL) {
                 dev_err(dev, "No DMA channel specified\n");
                 status = -ENOENT;
-                goto out_error_no_dma_ch;
+                goto out_error_free_io;
+        }
+        drv_data->dma_channel = res->start;
+
+        drv_data->spi_irq = platform_get_irq(pdev, 0);
+        if (drv_data->spi_irq < 0) {
+                dev_err(dev, "No spi pio irq specified\n");
+                status = -ENOENT;
+                goto out_error_free_io;
         }
 
         /* Initial and start queue */
@@ -1375,7 +1505,7 @@ static int __init bfin_spi_probe(struct platform_device *pdev)
 
 out_error_queue_alloc:
         bfin_spi_destroy_queue(drv_data);
-out_error_no_dma_ch:
+out_error_free_io:
         iounmap((void *) drv_data->regs_base);
 out_error_ioremap:
 out_error_get_res:
@@ -1407,6 +1537,11 @@ static int __devexit bfin_spi_remove(struct platform_device *pdev)
                         free_dma(drv_data->dma_channel);
         }
 
+        if (drv_data->irq_requested) {
+                free_irq(drv_data->spi_irq, drv_data);
+                drv_data->irq_requested = 0;
+        }
+
         /* Disconnect from the SPI framework */
         spi_unregister_master(drv_data->master);