rtc-v3020: add ability to access v3020 chip with GPIOs

The v3020 RTC can be connected to GPIOs as well as to memory-like
interface.  Add ability to use GPIO bit-bang for v3020 read-write access.

[akpm@linux-foundation.org: fix off-by-one in error path]
Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 176 insertions, 20 deletions

diff --git a/drivers/rtc/rtc-v3020.c b/drivers/rtc/rtc-v3020.c
index 66955cc9c746..ad164056feb6 100644
--- a/drivers/rtc/rtc-v3020.c
+++ b/drivers/rtc/rtc-v3020.c
@@ -27,17 +27,162 @@
 #include <linux/bcd.h>
 #include <linux/rtc-v3020.h>
 #include <linux/delay.h>
+#include <linux/gpio.h>
 
 #include <linux/io.h>
 
 #undef DEBUG
 
+struct v3020;
+
+struct v3020_chip_ops {
+        int (*map_io)(struct v3020 *chip, struct platform_device *pdev,
+                      struct v3020_platform_data *pdata);
+        void (*unmap_io)(struct v3020 *chip);
+        unsigned char (*read_bit)(struct v3020 *chip);
+        void (*write_bit)(struct v3020 *chip, unsigned char bit);
+};
+
+#define V3020_CS        0
+#define V3020_WR        1
+#define V3020_RD        2
+#define V3020_IO        3
+
+struct v3020_gpio {
+        const char *name;
+        unsigned int gpio;
+};
+
 struct v3020 {
+        /* MMIO access */
         void __iomem *ioaddress;
         int leftshift;
+
+        /* GPIO access */
+        struct v3020_gpio *gpio;
+
+        struct v3020_chip_ops *ops;
+
         struct rtc_device *rtc;
 };
 
+
+static int v3020_mmio_map(struct v3020 *chip, struct platform_device *pdev,
+                          struct v3020_platform_data *pdata)
+{
+        if (pdev->num_resources != 1)
+                return -EBUSY;
+
+        if (pdev->resource[0].flags != IORESOURCE_MEM)
+                return -EBUSY;
+
+        chip->leftshift = pdata->leftshift;
+        chip->ioaddress = ioremap(pdev->resource[0].start, 1);
+        if (chip->ioaddress == NULL)
+                return -EBUSY;
+
+        return 0;
+}
+
+static void v3020_mmio_unmap(struct v3020 *chip)
+{
+        iounmap(chip->ioaddress);
+}
+
+static void v3020_mmio_write_bit(struct v3020 *chip, unsigned char bit)
+{
+        writel(bit << chip->leftshift, chip->ioaddress);
+}
+
+static unsigned char v3020_mmio_read_bit(struct v3020 *chip)
+{
+        return readl(chip->ioaddress) & (1 << chip->leftshift);
+}
+
+static struct v3020_chip_ops v3020_mmio_ops = {
+        .map_io         = v3020_mmio_map,
+        .unmap_io       = v3020_mmio_unmap,
+        .read_bit       = v3020_mmio_read_bit,
+        .write_bit      = v3020_mmio_write_bit,
+};
+
+static struct v3020_gpio v3020_gpio[] = {
+        { "RTC CS", 0 },
+        { "RTC WR", 0 },
+        { "RTC RD", 0 },
+        { "RTC IO", 0 },
+};
+
+static int v3020_gpio_map(struct v3020 *chip, struct platform_device *pdev,
+                          struct v3020_platform_data *pdata)
+{
+        int i, err;
+
+        v3020_gpio[V3020_CS].gpio = pdata->gpio_cs;
+        v3020_gpio[V3020_WR].gpio = pdata->gpio_wr;
+        v3020_gpio[V3020_RD].gpio = pdata->gpio_rd;
+        v3020_gpio[V3020_IO].gpio = pdata->gpio_io;
+
+        for (i = 0; i < ARRAY_SIZE(v3020_gpio); i++) {
+                err = gpio_request(v3020_gpio[i].gpio, v3020_gpio[i].name);
+                if (err)
+                        goto err_request;
+
+                gpio_direction_output(v3020_gpio[i].gpio, 1);
+        }
+
+        chip->gpio = v3020_gpio;
+
+        return 0;
+
+err_request:
+        while (--i >= 0)
+                gpio_free(v3020_gpio[i].gpio);
+
+        return err;
+}
+
+static void v3020_gpio_unmap(struct v3020 *chip)
+{
+        int i;
+
+        for (i = 0; i < ARRAY_SIZE(v3020_gpio); i++)
+                gpio_free(v3020_gpio[i].gpio);
+}
+
+static void v3020_gpio_write_bit(struct v3020 *chip, unsigned char bit)
+{
+        gpio_direction_output(chip->gpio[V3020_IO].gpio, bit);
+        gpio_set_value(chip->gpio[V3020_CS].gpio, 0);
+        gpio_set_value(chip->gpio[V3020_WR].gpio, 0);
+        udelay(1);
+        gpio_set_value(chip->gpio[V3020_WR].gpio, 1);
+        gpio_set_value(chip->gpio[V3020_CS].gpio, 1);
+}
+
+static unsigned char v3020_gpio_read_bit(struct v3020 *chip)
+{
+        int bit;
+
+        gpio_direction_input(chip->gpio[V3020_IO].gpio);
+        gpio_set_value(chip->gpio[V3020_CS].gpio, 0);
+        gpio_set_value(chip->gpio[V3020_RD].gpio, 0);
+        udelay(1);
+        bit = !!gpio_get_value(chip->gpio[V3020_IO].gpio);
+        udelay(1);
+        gpio_set_value(chip->gpio[V3020_RD].gpio, 1);
+        gpio_set_value(chip->gpio[V3020_CS].gpio, 1);
+
+        return bit;
+}
+
+static struct v3020_chip_ops v3020_gpio_ops = {
+        .map_io         = v3020_gpio_map,
+        .unmap_io       = v3020_gpio_unmap,
+        .read_bit       = v3020_gpio_read_bit,
+        .write_bit      = v3020_gpio_write_bit,
+};
+
 static void v3020_set_reg(struct v3020 *chip, unsigned char address,
                         unsigned char data)
 {
@@ -46,7 +191,7 @@ static void v3020_set_reg(struct v3020 *chip, unsigned char address,
 
         tmp = address;
         for (i = 0; i < 4; i++) {
-                writel((tmp & 1) << chip->leftshift, chip->ioaddress);
+                chip->ops->write_bit(chip, (tmp & 1));
                 tmp >>= 1;
                 udelay(1);
         }
@@ -54,7 +199,7 @@ static void v3020_set_reg(struct v3020 *chip, unsigned char address,
         /* Commands dont have data */
         if (!V3020_IS_COMMAND(address)) {
                 for (i = 0; i < 8; i++) {
-                        writel((data & 1) << chip->leftshift, chip->ioaddress);
+                        chip->ops->write_bit(chip, (data & 1));
                         data >>= 1;
                         udelay(1);
                 }
@@ -67,14 +212,14 @@ static unsigned char v3020_get_reg(struct v3020 *chip, unsigned char address)
         int i;
 
         for (i = 0; i < 4; i++) {
-                writel((address & 1) << chip->leftshift, chip->ioaddress);
+                chip->ops->write_bit(chip, (address & 1));
                 address >>= 1;
                 udelay(1);
         }
 
         for (i = 0; i < 8; i++) {
                 data >>= 1;
-                if (readl(chip->ioaddress) & (1 << chip->leftshift))
+                if (chip->ops->read_bit(chip))
                         data |= 0x80;
                 udelay(1);
         }
@@ -164,25 +309,23 @@ static int rtc_probe(struct platform_device *pdev)
         int i;
         int temp;
 
-        if (pdev->num_resources != 1)
-                return -EBUSY;
-
-        if (pdev->resource[0].flags != IORESOURCE_MEM)
-                return -EBUSY;
-
         chip = kzalloc(sizeof *chip, GFP_KERNEL);
         if (!chip)
                 return -ENOMEM;
 
-        chip->leftshift = pdata->leftshift;
-        chip->ioaddress = ioremap(pdev->resource[0].start, 1);
-        if (chip->ioaddress == NULL)
+        if (pdata->use_gpio)
+                chip->ops = &v3020_gpio_ops;
+        else
+                chip->ops = &v3020_mmio_ops;
+
+        retval = chip->ops->map_io(chip, pdev, pdata);
+        if (retval)
                 goto err_chip;
 
         /* Make sure the v3020 expects a communication cycle
          * by reading 8 times */
         for (i = 0; i < 8; i++)
-                temp = readl(chip->ioaddress);
+                temp = chip->ops->read_bit(chip);
 
         /* Test chip by doing a write/read sequence
          * to the chip ram */
@@ -196,10 +339,17 @@ static int rtc_probe(struct platform_device *pdev)
          * are all disabled */
         v3020_set_reg(chip, V3020_STATUS_0, 0x0);
 
-        dev_info(&pdev->dev, "Chip available at physical address 0x%llx,"
-                "data connected to D%d\n",
-                (unsigned long long)pdev->resource[0].start,
-                chip->leftshift);
+        if (pdata->use_gpio)
+                dev_info(&pdev->dev, "Chip available at GPIOs "
+                         "%d, %d, %d, %d\n",
+                         chip->gpio[V3020_CS].gpio, chip->gpio[V3020_WR].gpio,
+                         chip->gpio[V3020_RD].gpio, chip->gpio[V3020_IO].gpio);
+        else
+                dev_info(&pdev->dev, "Chip available at "
+                         "physical address 0x%llx,"
+                         "data connected to D%d\n",
+                         (unsigned long long)pdev->resource[0].start,
+                         chip->leftshift);
 
         platform_set_drvdata(pdev, chip);
 
@@ -214,7 +364,7 @@ static int rtc_probe(struct platform_device *pdev)
         return 0;
 
 err_io:
-        iounmap(chip->ioaddress);
+        chip->ops->unmap_io(chip);
 err_chip:
         kfree(chip);
 
@@ -229,7 +379,7 @@ static int rtc_remove(struct platform_device *dev)
         if (rtc)
                 rtc_device_unregister(rtc);
 
-        iounmap(chip->ioaddress);
+        chip->ops->unmap_io(chip);
         kfree(chip);
 
         return 0;
diff --git a/include/linux/rtc-v3020.h b/include/linux/rtc-v3020.h
index bf74e63c98fe..8ba646e610d9 100644
--- a/include/linux/rtc-v3020.h
+++ b/include/linux/rtc-v3020.h
@@ -14,6 +14,12 @@
  * is used depends on the board. */
 struct v3020_platform_data {
         int leftshift; /* (1<<(leftshift)) & readl() */
+
+        int use_gpio:1;
+        unsigned int gpio_cs;
+        unsigned int gpio_wr;
+        unsigned int gpio_rd;
+        unsigned int gpio_io;
 };
 
 #define V3020_STATUS_0  0x00