spi: spi-gpio: Rewrite to use GPIO descriptors

This converts the bit-banged GPIO SPI driver to looking up and
using GPIO descriptors to get a handle on GPIO lines for SCK,
MOSI, MISO and all CS lines.

All existing board files are converted in one go to keep it all
consistent. With these conversions I rarely find any interrim
steps that makes any sense.

Device tree probing and GPIO handling should work like before
also after this patch.

For board files, we stop using controller data to pass the GPIO
line for chip select, instead we pass this as a GPIO descriptor
lookup like everything else.

In some s3c24xx machines the names of the SPI devices were set to
"spi-gpio" rather than "spi_gpio" which can never have worked, I
fixed it working (I guess) as part of this patch set. Sometimes
I wonder how this code got upstream in the first place, it
obviously is not tested.

mach-s3c64xx/mach-smartq.c has the same problem and additionally
defines the *same* GPIO line for MOSI and MISO which is not going
to be accepted by gpiolib. As the lines were number 1,2,2 I assumed
it was a typo and use lines 1,2,3. A comment gives awat that line 0
is chip select though no actual SPI device is provided for the LCD
supposed to be on this bit-banged SPI bus. I left it intact instead
of just deleting the bus though.

Kill off board file code that try to initialize the SPI lines
to the same values that they will later be set by the spi_gpio
driver anyways. Given the huge number of weird things in these
board files I do not think this code is very tested or put in
with much afterthought anyways.

In order to assert that we do not get performance regressions on
this crucial bing-banged driver, a ran a script like this dumping the
Ilitek ILI9322 regmap 10000 times (it has no caching obviously) on
an otherwise idle system in two iterations before and after the
patches:

 #!/bin/sh
 for run in `seq 10000`
 do
     cat /debug/regmap/spi0.0/registers > /dev/null
 done

Before the patch:

time test.sh
real    3m 41.03s
user    0m 29.41s
sys     3m 7.22s

time test.sh
real    3m 44.24s
user    0m 32.31s
sys     3m 7.60s

After the patch:

time test.sh
real    3m 41.32s
user    0m 28.92s
sys     3m 8.08s

time test.sh
real    3m 39.92s
user    0m 30.20s
sys     3m 5.56s

So any performance differences seems to be in the error margin.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 92 insertions, 178 deletions

diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c
index 1c34c9314c8a..b85a93cad44a 100644
--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -2,6 +2,7 @@
  * SPI master driver using generic bitbanged GPIO
  *
  * Copyright (C) 2006,2008 David Brownell
+ * Copyright (C) 2017 Linus Walleij
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -16,10 +17,9 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
-#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
-#include <linux/of_gpio.h>
 
 #include <linux/spi/spi.h>
 #include <linux/spi/spi_bitbang.h>
@@ -44,7 +44,11 @@ struct spi_gpio {
 	struct spi_bitbang		bitbang;
 	struct spi_gpio_platform_data	pdata;
 	struct platform_device		*pdev;
-	unsigned long			cs_gpios[0];
+	struct gpio_desc		*sck;
+	struct gpio_desc		*miso;
+	struct gpio_desc		*mosi;
+	struct gpio_desc		**cs_gpios;
+	bool				has_cs;
 };
 
 /*----------------------------------------------------------------------*/
@@ -77,13 +81,6 @@ struct spi_gpio {
 
 #define GENERIC_BITBANG	/* vs tight inlines */
 
-/* all functions referencing these symbols must define pdata */
-#define SPI_MISO_GPIO	((pdata)->miso)
-#define SPI_MOSI_GPIO	((pdata)->mosi)
-#define SPI_SCK_GPIO	((pdata)->sck)
-
-#define SPI_N_CHIPSEL	((pdata)->num_chipselect)
-
 #endif
 
 /*----------------------------------------------------------------------*/
@@ -105,25 +102,27 @@ spi_to_pdata(const struct spi_device *spi)
 	return &spi_to_spi_gpio(spi)->pdata;
 }
 
-/* this is #defined to avoid unused-variable warnings when inlining */
-#define pdata		spi_to_pdata(spi)
-
+/* These helpers are in turn called by the bitbang inlines */
 static inline void setsck(const struct spi_device *spi, int is_on)
 {
-	gpio_set_value_cansleep(SPI_SCK_GPIO, is_on);
+	struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
+
+	gpiod_set_value_cansleep(spi_gpio->sck, is_on);
 }
 
 static inline void setmosi(const struct spi_device *spi, int is_on)
 {
-	gpio_set_value_cansleep(SPI_MOSI_GPIO, is_on);
+	struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
+
+	gpiod_set_value_cansleep(spi_gpio->mosi, is_on);
 }
 
 static inline int getmiso(const struct spi_device *spi)
 {
-	return !!gpio_get_value_cansleep(SPI_MISO_GPIO);
-}
+	struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
 
-#undef pdata
+	return !!gpiod_get_value_cansleep(spi_gpio->miso);
+}
 
 /*
  * NOTE:  this clocks "as fast as we can".  It "should" be a function of the
@@ -216,123 +215,89 @@ static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi,
 static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
 {
 	struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
-	unsigned long cs = spi_gpio->cs_gpios[spi->chip_select];
 
-	/* set initial clock polarity */
+	/* set initial clock line level */
 	if (is_active)
-		setsck(spi, spi->mode & SPI_CPOL);
+		gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL);
+
+	/* Drive chip select line, if we have one */
+	if (spi_gpio->has_cs) {
+		struct gpio_desc *cs = spi_gpio->cs_gpios[spi->chip_select];
 
-	if (cs != SPI_GPIO_NO_CHIPSELECT) {
-		/* SPI is normally active-low */
-		gpio_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
+		/* SPI chip selects are normally active-low */
+		gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
 	}
 }
 
 static int spi_gpio_setup(struct spi_device *spi)
 {
-	unsigned long		cs;
+	struct gpio_desc	*cs;
 	int			status = 0;
 	struct spi_gpio		*spi_gpio = spi_to_spi_gpio(spi);
-	struct device_node	*np = spi->master->dev.of_node;
-
-	if (np) {
-		/*
-		 * In DT environments, the CS GPIOs have already been
-		 * initialized from the "cs-gpios" property of the node.
-		 */
-		cs = spi_gpio->cs_gpios[spi->chip_select];
-	} else {
-		/*
-		 * ... otherwise, take it from spi->controller_data
-		 */
-		cs = (uintptr_t) spi->controller_data;
-	}
 
-	if (!spi->controller_state) {
-		if (cs != SPI_GPIO_NO_CHIPSELECT) {
-			status = gpio_request(cs, dev_name(&spi->dev));
-			if (status)
-				return status;
-			status = gpio_direction_output(cs,
-					!(spi->mode & SPI_CS_HIGH));
-		}
-	}
-	if (!status) {
-		/* in case it was initialized from static board data */
-		spi_gpio->cs_gpios[spi->chip_select] = cs;
+	/*
+	 * The CS GPIOs have already been
+	 * initialized from the descriptor lookup.
+	 */
+	cs = spi_gpio->cs_gpios[spi->chip_select];
+	if (!spi->controller_state && cs)
+		status = gpiod_direction_output(cs,
+						!(spi->mode & SPI_CS_HIGH));
+
+	if (!status)
 		status = spi_bitbang_setup(spi);
-	}
 
-	if (status) {
-		if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT)
-			gpio_free(cs);
-	}
 	return status;
 }
 
 static void spi_gpio_cleanup(struct spi_device *spi)
 {
-	struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
-	unsigned long cs = spi_gpio->cs_gpios[spi->chip_select];
-
-	if (cs != SPI_GPIO_NO_CHIPSELECT)
-		gpio_free(cs);
 	spi_bitbang_cleanup(spi);
 }
 
-static int spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
-{
-	int value;
-
-	value = gpio_request(pin, label);
-	if (value == 0) {
-		if (is_in)
-			value = gpio_direction_input(pin);
-		else
-			value = gpio_direction_output(pin, 0);
-	}
-	return value;
-}
-
-static int spi_gpio_request(struct spi_gpio_platform_data *pdata,
-			    const char *label, u16 *res_flags)
+/*
+ * It can be convenient to use this driver with pins that have alternate
+ * functions associated with a "native" SPI controller if a driver for that
+ * controller is not available, or is missing important functionality.
+ *
+ * On platforms which can do so, configure MISO with a weak pullup unless
+ * there's an external pullup on that signal.  That saves power by avoiding
+ * floating signals.  (A weak pulldown would save power too, but many
+ * drivers expect to see all-ones data as the no slave "response".)
+ */
+static int spi_gpio_request(struct device *dev,
+			    struct spi_gpio *spi_gpio,
+			    unsigned int num_chipselects,
+			    u16 *mflags)
 {
-	int value;
-
-	/* NOTE:  SPI_*_GPIO symbols may reference "pdata" */
+	int i;
 
-	if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) {
-		value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
-		if (value)
-			goto done;
-	} else {
+	spi_gpio->mosi = devm_gpiod_get_optional(dev, "mosi", GPIOD_OUT_LOW);
+	if (IS_ERR(spi_gpio->mosi))
+		return PTR_ERR(spi_gpio->mosi);
+	if (!spi_gpio->mosi)
 		/* HW configuration without MOSI pin */
-		*res_flags |= SPI_MASTER_NO_TX;
-	}
+		*mflags |= SPI_MASTER_NO_TX;
 
-	if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) {
-		value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
-		if (value)
-			goto free_mosi;
-	} else {
+	spi_gpio->miso = devm_gpiod_get_optional(dev, "miso", GPIOD_IN);
+	if (IS_ERR(spi_gpio->miso))
+		return PTR_ERR(spi_gpio->miso);
+	if (!spi_gpio->miso)
 		/* HW configuration without MISO pin */
-		*res_flags |= SPI_MASTER_NO_RX;
-	}
+		*mflags |= SPI_MASTER_NO_RX;
 
-	value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
-	if (value)
-		goto free_miso;
+	spi_gpio->sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW);
+	if (IS_ERR(spi_gpio->mosi))
+		return PTR_ERR(spi_gpio->mosi);
 
-	goto done;
+	for (i = 0; i < num_chipselects; i++) {
+		spi_gpio->cs_gpios[i] = devm_gpiod_get_index(dev, "cs",
+							     i, GPIOD_OUT_HIGH);
+		if (IS_ERR(spi_gpio->cs_gpios[i]))
+			return PTR_ERR(spi_gpio->cs_gpios[i]);
+	}
 
-free_miso:
-	if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
-		gpio_free(SPI_MISO_GPIO);
-free_mosi:
-	if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
-		gpio_free(SPI_MOSI_GPIO);
-done:
-	return value;
+	return 0;
 }
 
 #ifdef CONFIG_OF
@@ -358,26 +323,6 @@ static int spi_gpio_probe_dt(struct platform_device *pdev)
 	if (!pdata)
 		return -ENOMEM;
 
-	ret = of_get_named_gpio(np, "gpio-sck", 0);
-	if (ret < 0) {
-		dev_err(&pdev->dev, "gpio-sck property not found\n");
-		goto error_free;
-	}
-	pdata->sck = ret;
-
-	ret = of_get_named_gpio(np, "gpio-miso", 0);
-	if (ret < 0) {
-		dev_info(&pdev->dev, "gpio-miso property not found, switching to no-rx mode\n");
-		pdata->miso = SPI_GPIO_NO_MISO;
-	} else
-		pdata->miso = ret;
-
-	ret = of_get_named_gpio(np, "gpio-mosi", 0);
-	if (ret < 0) {
-		dev_info(&pdev->dev, "gpio-mosi property not found, switching to no-tx mode\n");
-		pdata->mosi = SPI_GPIO_NO_MOSI;
-	} else
-		pdata->mosi = ret;
 
 	ret = of_property_read_u32(np, "num-chipselects", &tmp);
 	if (ret < 0) {
@@ -409,7 +354,6 @@ static int spi_gpio_probe(struct platform_device *pdev)
 	struct spi_gpio_platform_data	*pdata;
 	u16 master_flags = 0;
 	bool use_of = 0;
-	int num_devices;
 
 	status = spi_gpio_probe_dt(pdev);
 	if (status < 0)
@@ -423,59 +367,41 @@ static int spi_gpio_probe(struct platform_device *pdev)
 		return -ENODEV;
 #endif
 
-	if (use_of && !SPI_N_CHIPSEL)
-		num_devices = 1;
-	else
-		num_devices = SPI_N_CHIPSEL;
-
-	status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
-	if (status < 0)
-		return status;
+	master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio));
+	if (!master)
+		return -ENOMEM;
 
-	master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio) +
-					(sizeof(unsigned long) * num_devices));
-	if (!master) {
-		status = -ENOMEM;
-		goto gpio_free;
-	}
 	spi_gpio = spi_master_get_devdata(master);
+
+	spi_gpio->cs_gpios = devm_kzalloc(&pdev->dev,
+				pdata->num_chipselect * sizeof(*spi_gpio->cs_gpios),
+				GFP_KERNEL);
+	if (!spi_gpio->cs_gpios)
+		return -ENOMEM;
+
 	platform_set_drvdata(pdev, spi_gpio);
 
+	/* Determine if we have chip selects connected */
+	spi_gpio->has_cs = !!pdata->num_chipselect;
+
 	spi_gpio->pdev = pdev;
 	if (pdata)
 		spi_gpio->pdata = *pdata;
 
+	status = spi_gpio_request(&pdev->dev, spi_gpio,
+				  pdata->num_chipselect, &master_flags);
+	if (status)
+		return status;
+
 	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
 	master->flags = master_flags;
 	master->bus_num = pdev->id;
-	master->num_chipselect = num_devices;
+	/* The master needs to think there is a chipselect even if not connected */
+	master->num_chipselect = spi_gpio->has_cs ? pdata->num_chipselect : 1;
 	master->setup = spi_gpio_setup;
 	master->cleanup = spi_gpio_cleanup;
 #ifdef CONFIG_OF
 	master->dev.of_node = pdev->dev.of_node;
-
-	if (use_of) {
-		int i;
-		struct device_node *np = pdev->dev.of_node;
-
-		/*
-		 * In DT environments, take the CS GPIO from the "cs-gpios"
-		 * property of the node.
-		 */
-
-		if (!SPI_N_CHIPSEL)
-			spi_gpio->cs_gpios[0] = SPI_GPIO_NO_CHIPSELECT;
-		else
-			for (i = 0; i < SPI_N_CHIPSEL; i++) {
-				status = of_get_named_gpio(np, "cs-gpios", i);
-				if (status < 0) {
-					dev_err(&pdev->dev,
-						"invalid cs-gpios property\n");
-					goto gpio_free;
-				}
-				spi_gpio->cs_gpios[i] = status;
-			}
-	}
 #endif
 
 	spi_gpio->bitbang.master = master;
@@ -496,15 +422,8 @@ static int spi_gpio_probe(struct platform_device *pdev)
 	spi_gpio->bitbang.flags = SPI_CS_HIGH;
 
 	status = spi_bitbang_start(&spi_gpio->bitbang);
-	if (status < 0) {
-gpio_free:
-		if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
-			gpio_free(SPI_MISO_GPIO);
-		if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
-			gpio_free(SPI_MOSI_GPIO);
-		gpio_free(SPI_SCK_GPIO);
+	if (status)
 		spi_master_put(master);
-	}
 
 	return status;
 }
@@ -520,11 +439,6 @@ static int spi_gpio_remove(struct platform_device *pdev)
 	/* stop() unregisters child devices too */
 	spi_bitbang_stop(&spi_gpio->bitbang);
 
-	if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
-		gpio_free(SPI_MISO_GPIO);
-	if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
-		gpio_free(SPI_MOSI_GPIO);
-	gpio_free(SPI_SCK_GPIO);
 	spi_master_put(spi_gpio->bitbang.master);
 
 	return 0;