spi/dw_spi: refine the IRQ mode working flow

Now dw_spi core fully supports 3 transfer modes: pure polling,
DMA and IRQ mode. IRQ mode will use the FIFO half empty as
the IRQ trigger, so each interface driver need set the fifo_len,
so that core driver can handle it properly

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

3 files changed, 41 insertions, 25 deletions

diff --git a/drivers/spi/dw_spi.c b/drivers/spi/dw_spi.c
index 521d680af289..1bb709b3920f 100644
--- a/drivers/spi/dw_spi.c
+++ b/drivers/spi/dw_spi.c
@@ -358,6 +358,8 @@ static void transfer_complete(struct dw_spi *dws)
 static irqreturn_t interrupt_transfer(struct dw_spi *dws)
 {
         u16 irq_status, irq_mask = 0x3f;
+        u32 int_level = dws->fifo_len / 2;
+        u32 left;
 
         irq_status = dw_readw(dws, isr) & irq_mask;
         /* Error handling */
@@ -369,22 +371,23 @@ static irqreturn_t interrupt_transfer(struct dw_spi *dws)
                 return IRQ_HANDLED;
         }
 
-        /* INT comes from tx */
-        if (dws->tx && (irq_status & SPI_INT_TXEI)) {
-                while (dws->tx < dws->tx_end)
+        if (irq_status & SPI_INT_TXEI) {
+                spi_mask_intr(dws, SPI_INT_TXEI);
+
+                left = (dws->tx_end - dws->tx) / dws->n_bytes;
+                left = (left > int_level) ? int_level : left;
+
+                while (left--)
                         dws->write(dws);
+                dws->read(dws);
 
-                if (dws->tx == dws->tx_end) {
-                        spi_mask_intr(dws, SPI_INT_TXEI);
+                /* Re-enable the IRQ if there is still data left to tx */
+                if (dws->tx_end > dws->tx)
+                        spi_umask_intr(dws, SPI_INT_TXEI);
+                else
                         transfer_complete(dws);
-                }
         }
 
-        /* INT comes from rx */
-        if (dws->rx && (irq_status & SPI_INT_RXFI)) {
-                if (dws->read(dws))
-                        transfer_complete(dws);
-        }
         return IRQ_HANDLED;
 }
 
@@ -428,6 +431,7 @@ static void pump_transfers(unsigned long data)
         u8 bits = 0;
         u8 imask = 0;
         u8 cs_change = 0;
+        u16 txint_level = 0;
         u16 clk_div = 0;
         u32 speed = 0;
         u32 cr0 = 0;
@@ -438,6 +442,9 @@ static void pump_transfers(unsigned long data)
         chip = dws->cur_chip;
         spi = message->spi;
 
+        if (unlikely(!chip->clk_div))
+                chip->clk_div = dws->max_freq / chip->speed_hz;
+
         if (message->state == ERROR_STATE) {
                 message->status = -EIO;
                 goto early_exit;
@@ -492,7 +499,7 @@ static void pump_transfers(unsigned long data)
 
                         /* clk_div doesn't support odd number */
                         clk_div = dws->max_freq / speed;
-                        clk_div = (clk_div >> 1) << 1;
+                        clk_div = (clk_div + 1) & 0xfffe;
 
                         chip->speed_hz = speed;
                         chip->clk_div = clk_div;
@@ -535,11 +542,16 @@ static void pump_transfers(unsigned long data)
         /* Check if current transfer is a DMA transaction */
         dws->dma_mapped = map_dma_buffers(dws);
 
+        /*
+         * Interrupt mode
+         * we only need set the TXEI IRQ, as TX/RX always happen syncronizely
+         */
         if (!dws->dma_mapped && !chip->poll_mode) {
-                if (dws->rx)
-                        imask |= SPI_INT_RXFI;
-                if (dws->tx)
-                        imask |= SPI_INT_TXEI;
+                int templen = dws->len / dws->n_bytes;
+                txint_level = dws->fifo_len / 2;
+                txint_level = (templen > txint_level) ? txint_level : templen;
+
+                imask |= SPI_INT_TXEI;
                 dws->transfer_handler = interrupt_transfer;
         }
 
@@ -549,21 +561,23 @@ static void pump_transfers(unsigned long data)
          *      2. clk_div is changed
          *      3. control value changes
          */
-        if (dw_readw(dws, ctrl0) != cr0 || cs_change || clk_div) {
+        if (dw_readw(dws, ctrl0) != cr0 || cs_change || clk_div || imask) {
                 spi_enable_chip(dws, 0);
 
                 if (dw_readw(dws, ctrl0) != cr0)
                         dw_writew(dws, ctrl0, cr0);
 
+                spi_set_clk(dws, clk_div ? clk_div : chip->clk_div);
+                spi_chip_sel(dws, spi->chip_select);
+
                 /* Set the interrupt mask, for poll mode just diable all int */
                 spi_mask_intr(dws, 0xff);
-                if (!chip->poll_mode)
+                if (imask)
                         spi_umask_intr(dws, imask);
+                if (txint_level)
+                        dw_writew(dws, txfltr, txint_level);
 
-                spi_set_clk(dws, clk_div ? clk_div : chip->clk_div);
-                spi_chip_sel(dws, spi->chip_select);
                 spi_enable_chip(dws, 1);
-
                 if (cs_change)
                         dws->prev_chip = chip;
         }
@@ -712,11 +726,11 @@ static int dw_spi_setup(struct spi_device *spi)
         }
         chip->bits_per_word = spi->bits_per_word;
 
+        if (!spi->max_speed_hz) {
+                dev_err(&spi->dev, "No max speed HZ parameter\n");
+                return -EINVAL;
+        }
         chip->speed_hz = spi->max_speed_hz;
-        if (chip->speed_hz)
-                chip->clk_div = 25000000 / chip->speed_hz;
-        else
-                chip->clk_div = 8;      /* default value */
 
         chip->tmode = 0; /* Tx & Rx */
         /* Default SPI mode is SCPOL = 0, SCPH = 0 */
diff --git a/drivers/spi/dw_spi_pci.c b/drivers/spi/dw_spi_pci.c
index 7980f1443ce1..1f0735f9cc76 100644
--- a/drivers/spi/dw_spi_pci.c
+++ b/drivers/spi/dw_spi_pci.c
@@ -73,6 +73,7 @@ static int __devinit spi_pci_probe(struct pci_dev *pdev,
         dws->num_cs = 4;
         dws->max_freq = 25000000;       /* for Moorestwon */
         dws->irq = pdev->irq;
+        dws->fifo_len = 40;             /* FIFO has 40 words buffer */
 
         ret = dw_spi_add_host(dws);
         if (ret)
diff --git a/include/linux/spi/dw_spi.h b/include/linux/spi/dw_spi.h
index 51b3e771a9a3..1a127a31e017 100644
--- a/include/linux/spi/dw_spi.h
+++ b/include/linux/spi/dw_spi.h
@@ -90,6 +90,7 @@ struct dw_spi {
         unsigned long           paddr;
         u32                     iolen;
         int                     irq;
+        u32                     fifo_len;       /* depth of the FIFO buffer */
         u32                     max_freq;       /* max bus freq supported */
 
         u16                     bus_num;