linux-kernel - [PATCH] spi: cadence: Allow for GPIO pins to be used as chipselects

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Date:   Tue, 25 Apr 2017 11:30:14 -0700
From:   Moritz Fischer <mdf@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-spi@...r.kernel.org, broonie@...nel.org,
        moritz.fischer@...us.com, alex.williams@...com,
        Moritz Fischer <mdf@...nel.org>
Subject: [PATCH] spi: cadence: Allow for GPIO pins to be used as chipselects

This adds support for using GPIOs for chipselects as described by the
default dt-bindings.

Signed-off-by: Moritz Fischer <mdf@...nel.org>
---

Hi Mark,

I've tested this on my Zynq-7000 based system with
GPIO and non-gpio based chipselects mixed.

Thanks for your time,

Moritz

---
 drivers/spi/spi-cadence.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index 1c57ce6..f0b5c7b 100644
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -13,6 +13,7 @@
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/gpio.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
@@ -127,6 +128,10 @@ struct cdns_spi {
 	u32 is_decoded_cs;
 };
 
+struct cdns_spi_device_data {
+	bool gpio_requested;
+};
+
 /* Macros for the SPI controller read/write */
 static inline u32 cdns_spi_read(struct cdns_spi *xspi, u32 offset)
 {
@@ -456,6 +461,64 @@ static int cdns_unprepare_transfer_hardware(struct spi_master *master)
 	return 0;
 }
 
+static int cdns_spi_setup(struct spi_device *spi)
+{
+
+	int ret = -EINVAL;
+	struct cdns_spi_device_data *cdns_spi_data = spi_get_ctldata(spi);
+
+	/* this is a pin managed by the controller, leave it alone */
+	if (spi->cs_gpio == -ENOENT)
+		return 0;
+
+	/* this seems to be the first time we're here */
+	if (!cdns_spi_data) {
+		cdns_spi_data = kzalloc(sizeof(*cdns_spi_data), GFP_KERNEL);
+		if (!cdns_spi_data)
+			return -ENOMEM;
+		cdns_spi_data->gpio_requested = false;
+		spi_set_ctldata(spi, cdns_spi_data);
+	}
+
+	/* if we haven't done so, grab the gpio */
+	if (!cdns_spi_data->gpio_requested && gpio_is_valid(spi->cs_gpio)) {
+		ret = gpio_request_one(spi->cs_gpio,
+				       (spi->mode & SPI_CS_HIGH) ?
+				       GPIOF_OUT_INIT_LOW : GPIOF_OUT_INIT_HIGH,
+				       dev_name(&spi->dev));
+		if (ret)
+			dev_err(&spi->dev, "can't request chipselect gpio %d\n",
+				spi->cs_gpio);
+		else
+			cdns_spi_data->gpio_requested = true;
+	} else {
+		if (gpio_is_valid(spi->cs_gpio)) {
+			int mode = ((spi->mode & SPI_CS_HIGH) ?
+				    GPIOF_OUT_INIT_LOW : GPIOF_OUT_INIT_HIGH);
+
+			ret = gpio_direction_output(spi->cs_gpio, mode);
+			if (ret)
+				dev_err(&spi->dev, "chipselect gpio %d setup failed (%d)\n",
+					spi->cs_gpio, ret);
+		}
+	}
+
+	return ret;
+}
+
+static void cdns_spi_cleanup(struct spi_device *spi)
+{
+	struct cdns_spi_device_data *cdns_spi_data = spi_get_ctldata(spi);
+
+	if (cdns_spi_data) {
+		if (cdns_spi_data->gpio_requested)
+			gpio_free(spi->cs_gpio);
+		kfree(cdns_spi_data);
+		spi_set_ctldata(spi, NULL);
+	}
+
+}
+
 /**
  * cdns_spi_probe - Probe method for the SPI driver
  * @pdev:	Pointer to the platform_device structure
@@ -555,6 +618,8 @@ static int cdns_spi_probe(struct platform_device *pdev)
 	master->transfer_one = cdns_transfer_one;
 	master->unprepare_transfer_hardware = cdns_unprepare_transfer_hardware;
 	master->set_cs = cdns_spi_chipselect;
+	master->setup = cdns_spi_setup;
+	master->cleanup = cdns_spi_cleanup;
 	master->auto_runtime_pm = true;
 	master->mode_bits = SPI_CPOL | SPI_CPHA;
 
-- 
2.7.4