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

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Date:   Wed, 13 May 2020 16:00:22 +0200
From:   Lars Povlsen <lars.povlsen@...rochip.com>
To:     Mark Brown <broonie@...nel.org>, SoC Team <soc@...nel.org>
CC:     Lars Povlsen <lars.povlsen@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        <linux-spi@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: [PATCH 01/10] spi: dw: Add support for polled operation via no IRQ specified in DT

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@...tlin.com>
Signed-off-by: Lars Povlsen <lars.povlsen@...rochip.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