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rtc-v3020: add ability to access v3020 chip with GPIOs
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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>
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Mike Rapoport authored and Linus Torvalds committed Apr 3, 2009
1 parent c1c490e commit 9661584
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Showing 2 changed files with 176 additions and 20 deletions.
190 changes: 170 additions & 20 deletions drivers/rtc/rtc-v3020.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand All @@ -46,15 +191,15 @@ 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);
}

/* 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);
}
Expand All @@ -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);
}
Expand Down Expand Up @@ -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 */
Expand All @@ -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);

Expand All @@ -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);

Expand All @@ -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;
Expand Down
6 changes: 6 additions & 0 deletions include/linux/rtc-v3020.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down

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