[PATCH] video: Add support for the Solomon SSD1307 OLED Controller

[PATCH] video: Add support for the Solomon SSD1307 OLED Controller

[Maxime Ripard]

This patch adds support for the Solomon SSD1307 OLED
controller found on the Crystalfontz CFA10036 board.

This controller can drive a display with a resolution up
to 128x39 and can operate over I2C or SPI.

The current driver has only been tested on the CFA-10036,
that is using this controller over I2C to driver a 96x16
OLED screen.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Brian Lilly <brian@crystalfontz.com>
---
 .../devicetree/bindings/video/ssd1307fb.txt        |   24 ++
 drivers/video/Kconfig                              |   13 +
 drivers/video/Makefile                             |    1 +
 drivers/video/ssd1307fb.c                          |  407 ++++++++++++++++++++
 4 files changed, 445 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/video/ssd1307fb.txt
 create mode 100644 drivers/video/ssd1307fb.c

diff --git a/Documentation/devicetree/bindings/video/ssd1307fb.txt b/Documentation/devicetree/bindings/video/ssd1307fb.txt
new file mode 100644
index 0000000..3d0060c
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/ssd1307fb.txt
@@ -0,0 +1,24 @@
+* Solomon SSD1307 Framebuffer Driver
+
+Required properties:
+  - compatible: Should be "solomon,ssd1307fb-<bus>". The only supported bus for
+    now is i2c.
+  - reg: Should contain address of the controller on the I2C bus. Most likely
+         0x3c or 0x3d
+  - pwm: Should contain the pwm to use according to the OF device tree PWM
+         specification [0]
+  - reset-gpios: Should contain the GPIO used to reset the OLED display
+
+Optional properties:
+  - reset-active-low: Is the reset gpio is active on physical low?
+
+[0]: Documentation/devicetree/bindings/pwm/pwm.txt
+
+Examples:
+ssd1307: oled@3c {
+        compatible = "solomon,ssd1307fb-i2c";
+        reg = <0x3c>;
+        pwms = <&pwm 4 3000>;
+        reset-gpios = <&gpio2 7>;
+        reset-active-low;
+};
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index d08d799..294de9c 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -2442,4 +2442,17 @@ config FB_SH_MOBILE_MERAM
 	  Up to 4 memory channels can be configured, allowing 4 RGB or
 	  2 YCbCr framebuffers to be configured.
 
+config FB_SSD1307
+	tristate "Solomon SSD1307 framebuffer support"
+	depends on FB && I2C
+	select FB_SYS_FOPS
+	select FB_SYS_FILLRECT
+	select FB_SYS_COPYAREA
+	select FB_SYS_IMAGEBLIT
+	select FB_DEFERRED_IO
+	select PWM
+	help
+	  This driver implements support for the Solomon SSD1307
+	  OLED controller over I2C.
+
 endmenu
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 23e948e..768a137 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -161,6 +161,7 @@ obj-$(CONFIG_FB_BFIN_7393)        += bfin_adv7393fb.o
 obj-$(CONFIG_FB_MX3)		  += mx3fb.o
 obj-$(CONFIG_FB_DA8XX)		  += da8xx-fb.o
 obj-$(CONFIG_FB_MXS)		  += mxsfb.o
+obj-$(CONFIG_FB_SSD1307)	  += ssd1307fb.o
 
 # the test framebuffer is last
 obj-$(CONFIG_FB_VIRTUAL)          += vfb.o
diff --git a/drivers/video/ssd1307fb.c b/drivers/video/ssd1307fb.c
new file mode 100644
index 0000000..ed18f19
--- /dev/null
+++ b/drivers/video/ssd1307fb.c
@@ -0,0 +1,407 @@
+/*
+ * Driver for the Solomon SSD1307 OLED controler
+ *
+ * Copyright 2012 Free Electrons
+ *
+ * Licensed under the GPLv2 or later.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/i2c.h>
+#include <linux/fb.h>
+#include <linux/uaccess.h>
+#include <linux/of_device.h>
+#include <linux/of_gpio.h>
+#include <linux/pwm.h>
+#include <linux/delay.h>
+
+#define SSD1307FB_WIDTH			96
+#define SSD1307FB_HEIGHT		16
+
+#define SSD1307FB_DATA			0x40
+#define SSD1307FB_COMMAND		0x80
+
+#define SSD1307FB_CONTRAST		0x81
+#define SSD1307FB_SEG_REMAP_ON		0xa1
+#define SSD1307FB_DISPLAY_OFF		0xae
+#define SSD1307FB_DISPLAY_ON		0xaf
+#define SSD1307FB_START_PAGE_ADDRESS	0xb0
+
+struct ssd1307fb_par {
+	struct i2c_client *client;
+	struct fb_info *info;
+	struct pwm_device *pwm;
+	u32 pwm_period;
+	int reset;
+};
+
+static struct fb_fix_screeninfo ssd1307fb_fix __devinitdata = {
+	.id		= "Solomon SSD1307",
+	.type		= FB_TYPE_PACKED_PIXELS,
+	.visual		= FB_VISUAL_MONO10,
+	.xpanstep	= 0,
+	.ypanstep	= 0,
+	.ywrapstep	= 0,
+	.line_length	= SSD1307FB_WIDTH / 8,
+	.accel		= FB_ACCEL_NONE,
+};
+
+static struct fb_var_screeninfo ssd1307fb_var __devinitdata = {
+	.xres		= SSD1307FB_WIDTH,
+	.yres		= SSD1307FB_HEIGHT,
+	.xres_virtual	= SSD1307FB_WIDTH,
+	.yres_virtual	= SSD1307FB_HEIGHT,
+	.bits_per_pixel	= 1,
+};
+
+static int ssd1307fb_write_array(struct i2c_client *client, u8 type, u8* cmd, u32 len)
+{
+	u8 *buf;
+	int ret = 0;
+
+	buf = kzalloc(len + 1, GFP_KERNEL);
+	if (!buf) {
+		dev_err(&client->dev, "Couldn't allocate sending buffer.\n");
+		return -ENOMEM;
+	}
+
+	buf[0] = type;
+	memcpy(buf + 1, cmd, len);
+
+	ret = i2c_master_send(client, buf, len + 1);
+	if (ret != len + 1) {
+		dev_err(&client->dev, "Couldn't send I2C command.\n");
+		goto error;
+	}
+
+error:
+	kfree(buf);
+	return ret;
+}
+
+static inline int ssd1307fb_write_cmd_array(struct i2c_client *client, u8* cmd, u32 len)
+{
+	return ssd1307fb_write_array(client, SSD1307FB_COMMAND, cmd, len);
+}
+
+static inline int ssd1307fb_write_cmd(struct i2c_client *client, u8 cmd)
+{
+	return ssd1307fb_write_cmd_array(client, &cmd, 1);
+}
+
+static inline int ssd1307fb_write_data_array(struct i2c_client *client, u8* cmd, u32 len)
+{
+	return ssd1307fb_write_array(client, SSD1307FB_DATA, cmd, len);
+}
+
+static inline int ssd1307fb_write_data(struct i2c_client *client, u8 data)
+{
+	return ssd1307fb_write_data_array(client, &data, 1);
+}
+
+static void ssd1307fb_update_display(struct ssd1307fb_par *par)
+{
+	u8 *vmem = par->info->screen_base;
+	int i, j, k;
+
+	/*
+	 * The screen is divided in pages, each having a height of 8
+	 * pixels, and the width of the screen. When sending a byte of
+	 * data to the controller, it gives the 8 bits for the current
+	 * column. I.e, the first byte are the 8 bits of the first
+	 * column, then the 8 bits for the second column, etc.
+	 *
+	 *
+	 * Representation of the screen, assuming it is 5 bits
+	 * wide. Each letter-number combination is a bit that controls
+	 * one pixel.
+	 *
+	 * A0 A1 A2 A3 A4
+	 * B0 B1 B2 B3 B4
+	 * C0 C1 C2 C3 C4
+	 * D0 D1 D2 D3 D4
+	 * E0 E1 E2 E3 E4
+	 * F0 F1 F2 F3 F4
+	 * G0 G1 G2 G3 G4
+	 * H0 H1 H2 H3 H4
+	 *
+	 * If you want to update this screen, you need to send 5 bytes:
+	 *  (1) A0 B0 C0 D0 E0 F0 G0 H0
+	 *  (2) A1 B1 C1 D1 E1 F1 G1 H1
+	 *  (3) A2 B2 C2 D2 E2 F2 G2 H2
+	 *  (4) A3 B3 C3 D3 E3 F3 G3 H3
+	 *  (5) A4 B4 C4 D4 E4 F4 G4 H4
+	 */
+
+	for (i = 0; i < (SSD1307FB_HEIGHT / 8); i++) {
+		ssd1307fb_write_cmd(par->client, SSD1307FB_START_PAGE_ADDRESS + (i + 1));
+		ssd1307fb_write_cmd(par->client, 0x00);
+		ssd1307fb_write_cmd(par->client, 0x10);
+
+		for (j = 0; j < SSD1307FB_WIDTH; j++) {
+			u8 buf = 0;
+			for (k = 0; k < 8; k++) {
+				u32 page_length = SSD1307FB_WIDTH * i;
+				u32 index = page_length + (SSD1307FB_WIDTH * k + j) / 8;
+				u8 byte = *(vmem + index);
+				u8 bit = byte & (1 << (7 - (j % 8)));
+				bit = bit >> (7 - (j % 8));
+				buf |= bit << k;
+			}
+			ssd1307fb_write_data(par->client, buf);
+		}
+	}
+}
+
+
+static ssize_t ssd1307fb_write(struct fb_info *info, const char __user *buf,
+		size_t count, loff_t *ppos)
+{
+	struct ssd1307fb_par *par = info->par;
+	unsigned long total_size;
+	unsigned long p = *ppos;
+	u8 __iomem *dst;
+	int err = 0;
+
+	total_size = info->screen_size;
+
+	if (total_size = 0)
+		total_size = info->fix.smem_len;
+
+	if (p > total_size)
+		return -EFBIG;
+
+	if (count > total_size) {
+		err = -EFBIG;
+		count = total_size;
+	}
+
+	if (count + p > total_size) {
+		if (!err)
+			err = -ENOSPC;
+
+		count = total_size - p;
+	}
+
+	dst = (void __force *) (info->screen_base + p);
+
+	if (copy_from_user(dst, buf, count))
+		err = -EFAULT;
+
+	if  (!err)
+		*ppos += count;
+
+	ssd1307fb_update_display(par);
+
+	return (err) ? err : count;
+}
+
+static void ssd1307fb_fillrect(struct fb_info *info, const struct fb_fillrect *rect)
+{
+	struct ssd1307fb_par *par = info->par;
+	sys_fillrect(info, rect);
+	ssd1307fb_update_display(par);
+}
+
+static void ssd1307fb_copyarea(struct fb_info *info, const struct fb_copyarea *area) 
+{
+	struct ssd1307fb_par *par = info->par;
+	sys_copyarea(info, area);
+	ssd1307fb_update_display(par);
+}
+
+static void ssd1307fb_imageblit(struct fb_info *info, const struct fb_image *image) 
+{
+	struct ssd1307fb_par *par = info->par;
+	sys_imageblit(info, image);
+	ssd1307fb_update_display(par);
+}
+
+static struct fb_ops ssd1307fb_ops = {
+	.owner		= THIS_MODULE,
+	.fb_read	= fb_sys_read,
+	.fb_write	= ssd1307fb_write,
+	.fb_fillrect	= ssd1307fb_fillrect,
+	.fb_copyarea	= ssd1307fb_copyarea,
+	.fb_imageblit	= ssd1307fb_imageblit,
+};
+
+static void ssd1307fb_deferred_io(struct fb_info *info,
+				struct list_head *pagelist)
+{
+	ssd1307fb_update_display(info->par);
+}
+
+static struct fb_deferred_io ssd1307fb_defio = {
+	.delay		= HZ,
+	.deferred_io	= ssd1307fb_deferred_io,
+};
+
+static int __devinit ssd1307fb_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+	struct fb_info *info;
+	u32 vmem_size = SSD1307FB_WIDTH * SSD1307FB_HEIGHT / 8;
+	struct ssd1307fb_par *par;
+	u8 *vmem;
+	int ret;
+
+	if (!client->dev.of_node) {
+		dev_err(&client->dev, "No device tree data found!\n");
+		return -EINVAL;
+	}
+
+	info = framebuffer_alloc(sizeof(struct ssd1307fb_par), &client->dev);
+	if (!info) {
+		dev_err(&client->dev, "Couldn't allocate framebuffer.\n");
+		return -ENOMEM;
+	}
+
+	vmem = devm_kzalloc(&client->dev, vmem_size, GFP_KERNEL);
+	if (!vmem) {
+		dev_err(&client->dev, "Couldn't allocate graphical memory.\n");
+		ret = -ENOMEM;
+		goto fb_alloc_error;
+	}
+
+	info->fbops = &ssd1307fb_ops;
+	info->fix = ssd1307fb_fix;
+	info->fbdefio = &ssd1307fb_defio;
+
+	info->var = ssd1307fb_var;
+	info->var.red.length = 1;
+	info->var.red.offset = 0;
+	info->var.green.length = 1;
+	info->var.green.offset = 0;
+	info->var.blue.length = 1;
+	info->var.blue.offset = 0;
+
+	info->screen_base = (u8 __force __iomem *)vmem;
+	info->fix.smem_start = (unsigned long)vmem;
+	info->fix.smem_len = vmem_size;
+
+	fb_deferred_io_init(info);
+
+	par = info->par;
+	par->info = info;
+	par->client = client;
+
+	par->reset = of_get_named_gpio(client->dev.of_node,
+					 "reset-gpios", 0);
+	if (!gpio_is_valid(par->reset)) {
+		ret = -EINVAL;
+		goto reset_oled_error;
+	}
+
+	ret = devm_gpio_request_one(&client->dev, par->reset,
+				    GPIOF_OUT_INIT_HIGH,
+				    "oled-reset");
+	if (ret) {
+		dev_err(&client->dev,
+			"failed to request gpio %d: %d\n",
+			par->reset, ret);
+		goto reset_oled_error;
+	}
+
+	par->pwm = pwm_get(&client->dev, NULL);
+	if (IS_ERR(par->pwm)) {
+		dev_err(&client->dev, "Could not get PWM from device tree!\n");
+		ret = PTR_ERR(par->pwm);
+		goto pwm_error;
+	}
+
+	par->pwm_period = pwm_get_period(par->pwm);
+
+	dev_dbg(&client->dev, "Using PWM%d with a %dns period.\n", par->pwm->pwm, par->pwm_period);
+
+	ret = register_framebuffer(info);
+	if (ret) {
+		dev_err(&client->dev, "Couldn't register the framebuffer\n");
+		goto fbreg_error;
+	}
+
+	i2c_set_clientdata(client, info);
+
+	/* Reset the screen */
+	gpio_set_value(par->reset, 0);
+	udelay(4);
+	gpio_set_value(par->reset, 1);
+	udelay(4);
+
+	/* Enable the PWM */
+	pwm_config(par->pwm, par->pwm_period / 2, par->pwm_period);
+	pwm_enable(par->pwm);
+
+	/* Map column 127 of the OLED to segment 0 */
+	ret = ssd1307fb_write_cmd(client, SSD1307FB_SEG_REMAP_ON);
+	if (ret < 0) {
+		dev_err(&client->dev, "Couldn't remap the screen.\n");
+		goto remap_error;
+	}
+
+	/* Turn on the display */
+	ret = ssd1307fb_write_cmd(client, SSD1307FB_DISPLAY_ON);
+	if (ret < 0) {
+		dev_err(&client->dev, "Couldn't turn the display on.\n");
+		goto remap_error;
+	}
+
+	dev_info(&client->dev, "fb%d: %s framebuffer device registered, using %d bytes of video memory\n", info->node, info->fix.id, vmem_size);
+
+	return 0;
+
+remap_error:
+	unregister_framebuffer(info);
+	pwm_disable(par->pwm);
+fbreg_error:
+	pwm_put(par->pwm);
+pwm_error:
+reset_oled_error:
+	fb_deferred_io_cleanup(info);
+fb_alloc_error:
+	framebuffer_release(info);
+	return ret;
+}
+
+static int __devexit ssd1307fb_remove(struct i2c_client *client)
+{
+	struct fb_info *info = i2c_get_clientdata(client);
+	struct ssd1307fb_par *par = info->par;
+
+	unregister_framebuffer(info);
+	pwm_disable(par->pwm);
+	pwm_put(par->pwm);
+	fb_deferred_io_cleanup(info);
+	framebuffer_release(info);
+
+	return 0;
+}
+
+static const struct i2c_device_id ssd1307fb_i2c_id[] = {
+	{ "ssd1307fb", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ssd1307fb_i2c_id);
+
+static const struct of_device_id ssd1307fb_of_match[] = {
+	{ .compatible = "solomon,ssd1307fb-i2c" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, ssd1307fb_of_match);
+
+static struct i2c_driver ssd1307fb_driver = {
+	.probe = ssd1307fb_probe,
+	.remove = __devexit_p(ssd1307fb_remove),
+	.id_table = ssd1307fb_i2c_id,
+	.driver = {
+		.name = "ssd1307fb",
+		.of_match_table = of_match_ptr(ssd1307fb_of_match),
+		.owner = THIS_MODULE,
+	},
+};
+
+module_i2c_driver(ssd1307fb_driver);
+
+MODULE_DESCRIPTION("FB driver for the Solomon SSD1307 OLED controler");
+MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
+MODULE_LICENSE("GPL");
-- 
1.7.9.5

Re: [PATCH] video: Add support for the Solomon SSD1307 OLED Controller

[Andrew Morton]

On Thu, 15 Nov 2012 16:32:07 +0100
Maxime Ripard <maxime.ripard@free-electrons.com> wrote:

> This patch adds support for the Solomon SSD1307 OLED
> controller found on the Crystalfontz CFA10036 board.
> 
> This controller can drive a display with a resolution up
> to 128x39 and can operate over I2C or SPI.
> 
> The current driver has only been tested on the CFA-10036,
> that is using this controller over I2C to driver a 96x16
> OLED screen.
>
> ...
>
> +static ssize_t ssd1307fb_write(struct fb_info *info, const char __user *buf,
> +		size_t count, loff_t *ppos)
> +{
> +	struct ssd1307fb_par *par = info->par;
> +	unsigned long total_size;
> +	unsigned long p = *ppos;
> +	u8 __iomem *dst;
> +	int err = 0;
> +
> +	total_size = info->screen_size;
> +
> +	if (total_size = 0)
> +		total_size = info->fix.smem_len;
> +
> +	if (p > total_size)
> +		return -EFBIG;
> +
> +	if (count > total_size) {
> +		err = -EFBIG;
> +		count = total_size;
> +	}
> +
> +	if (count + p > total_size) {
> +		if (!err)
> +			err = -ENOSPC;
> +
> +		count = total_size - p;
> +	}
> +
> +	dst = (void __force *) (info->screen_base + p);
> +
> +	if (copy_from_user(dst, buf, count))
> +		err = -EFAULT;
> +
> +	if  (!err)
> +		*ppos += count;
> +
> +	ssd1307fb_update_display(par);
> +
> +	return (err) ? err : count;
> +}

There are a lot of things not to like about this function ;)

EFBIG means "file too large" and ENOSPC means "No space left on
device".  A video driver has no business returning these errors.  If
these errors occur then our poor user might end up running around
checking his disk free space and looking for huge files.  Because we
misled him.  These errors are due to invalid syscall arguments, so
how's about we tell the truth and use EINVAL?

Also, the function will under some circumstances return an error, but
it has done the write anyway!  What is userspace supposed to do?  If it
was well written it may retry the write, or report the error and
terminate.  A write() should return the number of bytes written on
success.  It's quite OK for that return value to be less than the
number of bytes the user requested, and I suggest that's what you
should do here.  Or you could just abort the write altogther and return
-EINVAL if there are any invalid arguments.

>
> ...
>
> +	par->reset = of_get_named_gpio(client->dev.of_node,
> +					 "reset-gpios", 0);

It appears that this driver will be unusable if CONFIG_OF=n, yet we
permit it to be configured on such systems.  I think it would be better
to make CONFIG_FB_SSD1307 depend on CONFIG_OF so users don't end up
compiling and bundling unusable drivers?

(otoh, there is a maintainability argument in favor of permitting a
driver to be compiled with x86 allmodconfig)

> +	if (!gpio_is_valid(par->reset)) {
> +		ret = -EINVAL;
> +		goto reset_oled_error;
> +	}
> +
>
> ...
>
> +	gpio_set_value(par->reset, 0);

A Kconfig dependency on CONFIG_GPIO might also be needed, for the same
reasons.

> +	udelay(4);
> +	gpio_set_value(par->reset, 1);
> +	udelay(4);
>
> ...
>