Serge Semin writes:

On Wed, May 13, 2020 at 04:00:22PM +0200, Lars Povlsen wrote:

quoted

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.belloni@bootlin.com>
Signed-off-by: Lars Povlsen <redacted>
---
 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

quoted

+#define VALID_IRQ(i) (i >= 0)

Mark and Andy are right. It is a good candidate to be in a generic IRQ-related
code as Anyd suggested:

quoted

quoted

drivers/rtc/rtc-cmos.c:95:#define is_valid_irq(n)               ((n) > 0)
Candidate to be in include/linux/irq.h ?

So if you feel like to author additional useful patch integrated into the
kernel, this one is a good chance for it.

Yeah, but with the poll_transfer() gone below, I think I'll settle on
just getting this into the current framework. Optimization (as this is)
has less priority. I'll put this on the back burner.

quoted

+
 /* 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);

Please note. The chip->poll and the poll_transfer() methods've been discarded
from the driver, since commit 1ceb09717e98 ("spi: dw: remove cs_control and
poll_mode members from chip_data"). So you gonna have to get the
poll_transfer-like method back.

-Sergey

quoted

      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

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-- 
Lars Povlsen,
Microchip