[PATCH 01/10] spi: dw: Add support for polled operation via no IRQ specified in DT

[Lars Povlsen]

With this change a SPI controller can be added without having a IRQ
associated, and causing all transfers to be polled. For SPI controllers
without DMA, this can significantly improve performance by less
interrupt handling overhead.

Reviewed-by: Alexandre Belloni <alexandre.bell...@bootlin.com>
Signed-off-by: Lars Povlsen <lars.povl...@microchip.com>
---
 drivers/spi/spi-dw.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index 31e3f866d11a7..e572eb34a3c1a 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -19,6 +19,8 @@
 #include <linux/debugfs.h>
 #endif

+#define VALID_IRQ(i) (i >= 0)
+
 /* Slave spi_dev related */
 struct chip_data {
        u8 tmode;               /* TR/TO/RO/EEPROM */
@@ -359,7 +361,7 @@ static int dw_spi_transfer_one(struct spi_controller 
*master,
                        spi_enable_chip(dws, 1);
                        return ret;
                }
-       } else if (!chip->poll_mode) {
+       } else if (!chip->poll_mode && VALID_IRQ(dws->irq)) {
                txlevel = min_t(u16, dws->fifo_len / 2, dws->len / 
dws->n_bytes);
                dw_writel(dws, DW_SPI_TXFLTR, txlevel);

@@ -379,7 +381,7 @@ static int dw_spi_transfer_one(struct spi_controller 
*master,
                        return ret;
        }

-       if (chip->poll_mode)
+       if (chip->poll_mode || !VALID_IRQ(dws->irq))
                return poll_transfer(dws);

        return 1;
@@ -487,11 +489,13 @@ int dw_spi_add_host(struct device *dev, struct dw_spi 
*dws)

        spi_controller_set_devdata(master, dws);

-       ret = request_irq(dws->irq, dw_spi_irq, IRQF_SHARED, dev_name(dev),
-                         master);
-       if (ret < 0) {
-               dev_err(dev, "can not get IRQ\n");
-               goto err_free_master;
+       if (VALID_IRQ(dws->irq)) {
+               ret = request_irq(dws->irq, dw_spi_irq, IRQF_SHARED,
+                                 dev_name(dev), master);
+               if (ret < 0) {
+                       dev_err(dev, "can not get IRQ\n");
+                       goto err_free_master;
+               }
        }

        master->use_gpio_descriptors = true;
@@ -539,7 +543,8 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
        if (dws->dma_ops && dws->dma_ops->dma_exit)
                dws->dma_ops->dma_exit(dws);
        spi_enable_chip(dws, 0);
-       free_irq(dws->irq, master);
+       if (VALID_IRQ(dws->irq))
+               free_irq(dws->irq, master);
 err_free_master:
        spi_controller_put(master);
        return ret;
--
2.26.2