[PATCHv2 04/10] fbdev: ssd1307fb: Unify init code and obtain hw specific bits from DT

["Thomas Niederprüm" <niederp@physik.uni-kl.de>]

The SSD130X controllers are very similar from the configuration point of view.
The configuration registers for the SSD1305/6/7 are bit identical (except the
the VHCOM register and the the default values for clock setup register). This
patch unifies the init code of the controller and adds hardware specific
properties to DT that are needed to correctly initialize the device.

The SSD130X can be wired to the OLED panel in various ways. Even for the
same controller this wiring can differ from one display module to another
and can not be probed by software. The added DT properties reflect these
hardware decisions of the display module manufacturer.
The 'com-sequential', 'com-lrremap' and 'com-invdir' values define different
possibilities for the COM signals pin configuration and readout direction
of the video memory. The 'segment-remap' allows the inversion of the memory-
to-pin mapping ultimately inverting the order of the controllers output pins.
The 'prechargepX' values need to be adapted according the capacitance of the
OLEDs pixel cells.

So far these hardware specific bits are hard coded in the init code, making
the driver usable only for one certain wiring of the controller. This patch
makes the driver usable with all possible hardware setups, given a valid hw
description in DT. If the values are not set in DT the default values
according to the controllers datasheet are assumed. This implies that this
patch changes the existing behaviour with respect to the segment remap for
the SSD1307 when the corresponding property is not present in DT. The example
in the DT bindings documentation is updated to reflect this change.

Note that the SSD1306 does not seem to be using the configuration written to
the registers at all. Nevertheless an example is added to the DT bindings
documentation that would lead to the same configuration as the current init
code.

Signed-off-by: Thomas Niederprüm <niederp@physik.uni-kl.de>
---
 .../devicetree/bindings/video/ssd1307fb.txt        |  22 +++
 drivers/video/fbdev/ssd1307fb.c                    | 195 ++++++++++++---------
 2 files changed, 138 insertions(+), 79 deletions(-)

diff --git a/Documentation/devicetree/bindings/video/ssd1307fb.txt b/Documentation/devicetree/bindings/video/ssd1307fb.txt
index 7a12542..6bdd69b 100644
--- a/Documentation/devicetree/bindings/video/ssd1307fb.txt
+++ b/Documentation/devicetree/bindings/video/ssd1307fb.txt
@@ -15,6 +15,15 @@ Required properties:
 
 Optional properties:
   - reset-active-low: Is the reset gpio is active on physical low?
+  - solomon,segment-remap: Display needs inverted data column to segment mapping
+  - solomon,com-sequential: Display uses sequential COM pin configuration
+  - solomon,com-lrremap: Display uses left-right COM pin remap
+  - solomon,com-invdir: Display uses inverted COM pin scan direction
+  - solomon,com-offset: Offset of the first COM pin wired to the panel
+  - solomon,prechargep1: Length of deselect period (phase 1) in clock cycles.
+  - solomon,prechargep2: Length of precharge period (phase 2) in clock cycles.
+                         This needs to be the higher, the higher the capacitance
+                         of the OLED's pixels is
 
 [0]: Documentation/devicetree/bindings/pwm/pwm.txt
 
@@ -25,4 +34,17 @@ ssd1307: oled@3c {
         pwms = <&pwm 4 3000>;
         reset-gpios = <&gpio2 7>;
         reset-active-low;
+        solomon,segment-remap;
+};
+
+ssd1306: oled@3c {
+        compatible = "solomon,ssd1306fb-i2c";
+        reg = <0x3c>;
+        pwms = <&pwm 4 3000>;
+        reset-gpios = <&gpio2 7>;
+        reset-active-low;
+        solomon,segment-remap;
+        solomon,com-lrremap;
+        solomon,com-invdir;
+        solomon,com-offset = <32>;
 };
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 25dd08d..b4880c0 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -17,6 +17,9 @@
 #include <linux/pwm.h>
 #include <linux/delay.h>
 
+#define DEVID_SSD1306 6
+#define DEVID_SSD1307 7
+
 #define SSD1307FB_DATA			0x40
 #define SSD1307FB_COMMAND		0x80
 
@@ -39,22 +42,38 @@
 #define	SSD1307FB_SET_COM_PINS_CONFIG	0xda
 #define	SSD1307FB_SET_VCOMH		0xdb
 
+static u_int contrast = 128;
+module_param(contrast, uint, S_IRUGO);
+
 struct ssd1307fb_par;
 
-struct ssd1307fb_ops {
-	int (*init)(struct ssd1307fb_par *);
-	int (*remove)(struct ssd1307fb_par *);
+struct ssd1307fb_deviceinfo {
+	int device_id;
+	u32 default_vcomh;
+	u32 default_dclk_div;
+	u32 default_dclk_frq;
 };
 
 struct ssd1307fb_par {
+	u32 com_invdir;
+	u32 com_lrremap;
+	u32 com_offset;
+	u32 com_seq;
+	u32 contrast;
+	u32 dclk_div;
+	u32 dclk_frq;
+	struct ssd1307fb_deviceinfo *device_info;
 	struct i2c_client *client;
 	u32 height;
 	struct fb_info *info;
-	struct ssd1307fb_ops *ops;
 	u32 page_offset;
+	u32 prechargep1;
+	u32 prechargep2;
 	struct pwm_device *pwm;
 	u32 pwm_period;
 	int reset;
+	u32 seg_remap;
+	u32 vcomh;
 	u32 width;
 };
 
@@ -255,69 +274,46 @@ static struct fb_deferred_io ssd1307fb_defio = {
 	.deferred_io	= ssd1307fb_deferred_io,
 };
 
-static int ssd1307fb_ssd1307_init(struct ssd1307fb_par *par)
+static int ssd1307fb_init(struct ssd1307fb_par *par)
 {
 	int ret;
+	u32 precharge, dclk, com_invdir, compins;
 
-	par->pwm = pwm_get(&par->client->dev, NULL);
-	if (IS_ERR(par->pwm)) {
-		dev_err(&par->client->dev, "Could not get PWM from device tree!\n");
-		return PTR_ERR(par->pwm);
-	}
-
-	par->pwm_period = pwm_get_period(par->pwm);
-	/* Enable the PWM */
-	pwm_config(par->pwm, par->pwm_period / 2, par->pwm_period);
-	pwm_enable(par->pwm);
-
-	dev_dbg(&par->client->dev, "Using PWM%d with a %dns period.\n",
-		par->pwm->pwm, par->pwm_period);
-
-	/* Map column 127 of the OLED to segment 0 */
-	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SEG_REMAP_ON);
-	if (ret < 0)
-		return ret;
-
-	/* Turn on the display */
-	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_DISPLAY_ON);
-	if (ret < 0)
-		return ret;
-
-	return 0;
-}
-
-static int ssd1307fb_ssd1307_remove(struct ssd1307fb_par *par)
-{
-	pwm_disable(par->pwm);
-	pwm_put(par->pwm);
-	return 0;
-}
+	if (par->device_info->device_id == DEVID_SSD1307) {
+		par->pwm = pwm_get(&par->client->dev, NULL);
+		if (IS_ERR(par->pwm)) {
+			dev_err(&par->client->dev, "Could not get PWM from device tree!\n");
+			return PTR_ERR(par->pwm);
+		}
 
-static struct ssd1307fb_ops ssd1307fb_ssd1307_ops = {
-	.init	= ssd1307fb_ssd1307_init,
-	.remove	= ssd1307fb_ssd1307_remove,
-};
+		par->pwm_period = pwm_get_period(par->pwm);
+		/* Enable the PWM */
+		pwm_config(par->pwm, par->pwm_period / 2, par->pwm_period);
+		pwm_enable(par->pwm);
 
-static int ssd1307fb_ssd1306_init(struct ssd1307fb_par *par)
-{
-	int ret;
+		dev_dbg(&par->client->dev, "Using PWM%d with a %dns period.\n",
+			par->pwm->pwm, par->pwm_period);
+	};
 
 	/* Set initial contrast */
 	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_CONTRAST);
 	if (ret < 0)
 		return ret;
 
-	ret = ssd1307fb_write_cmd(par->client, 0x7f);
-	if (ret < 0)
-		return ret;
-
-	/* Set COM direction */
-	ret = ssd1307fb_write_cmd(par->client, 0xc8);
+	ret = ssd1307fb_write_cmd(par->client, par->contrast);
 	if (ret < 0)
 		return ret;
 
 	/* Set segment re-map */
-	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SEG_REMAP_ON);
+	if (par->seg_remap) {
+		ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SEG_REMAP_ON);
+		if (ret < 0)
+			return ret;
+	};
+
+	/* Set COM direction */
+	com_invdir = 0xc0 | (par->com_invdir & 0xf) << 3;
+	ret = ssd1307fb_write_cmd(par->client,  com_invdir);
 	if (ret < 0)
 		return ret;
 
@@ -335,34 +331,38 @@ static int ssd1307fb_ssd1306_init(struct ssd1307fb_par *par)
 	if (ret < 0)
 		return ret;
 
-	ret = ssd1307fb_write_cmd(par->client, 0x20);
+	ret = ssd1307fb_write_cmd(par->client, par->com_offset);
 	if (ret < 0)
 		return ret;
 
 	/* Set clock frequency */
+	dclk = (par->dclk_div & 0xf) | (par->dclk_frq & 0xf) << 4;
 	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_CLOCK_FREQ);
 	if (ret < 0)
 		return ret;
 
-	ret = ssd1307fb_write_cmd(par->client, 0xf0);
+	ret = ssd1307fb_write_cmd(par->client, dclk);
 	if (ret < 0)
 		return ret;
 
 	/* Set precharge period in number of ticks from the internal clock */
+	precharge = (par->prechargep1 & 0xf) | (par->prechargep2 & 0xf) << 4;
 	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_PRECHARGE_PERIOD);
 	if (ret < 0)
 		return ret;
 
-	ret = ssd1307fb_write_cmd(par->client, 0x22);
+	ret = ssd1307fb_write_cmd(par->client, precharge);
 	if (ret < 0)
 		return ret;
 
 	/* Set COM pins configuration */
+	compins = 0x02 | (!par->com_seq & 0x1) << 4
+				   | (par->com_lrremap & 0x1) << 5;
 	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_COM_PINS_CONFIG);
 	if (ret < 0)
 		return ret;
 
-	ret = ssd1307fb_write_cmd(par->client, 0x22);
+	ret = ssd1307fb_write_cmd(par->client, compins);
 	if (ret < 0)
 		return ret;
 
@@ -371,18 +371,20 @@ static int ssd1307fb_ssd1306_init(struct ssd1307fb_par *par)
 	if (ret < 0)
 		return ret;
 
-	ret = ssd1307fb_write_cmd(par->client, 0x49);
+	ret = ssd1307fb_write_cmd(par->client, par->vcomh);
 	if (ret < 0)
 		return ret;
 
-	/* Turn on the DC-DC Charge Pump */
-	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_CHARGE_PUMP);
-	if (ret < 0)
-		return ret;
+	if (par->device_info->device_id == DEVID_SSD1306) {
+		/* Turn on the DC-DC Charge Pump */
+		ret = ssd1307fb_write_cmd(par->client, SSD1307FB_CHARGE_PUMP);
+		if (ret < 0)
+			return ret;
 
-	ret = ssd1307fb_write_cmd(par->client, 0x14);
-	if (ret < 0)
-		return ret;
+		ret = ssd1307fb_write_cmd(par->client, 0x14);
+		if (ret < 0)
+			return ret;
+	};
 
 	/* Switch to horizontal addressing mode */
 	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_ADDRESS_MODE);
@@ -394,6 +396,7 @@ static int ssd1307fb_ssd1306_init(struct ssd1307fb_par *par)
 	if (ret < 0)
 		return ret;
 
+    /* Set column range */
 	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_COL_RANGE);
 	if (ret < 0)
 		return ret;
@@ -406,6 +409,7 @@ static int ssd1307fb_ssd1306_init(struct ssd1307fb_par *par)
 	if (ret < 0)
 		return ret;
 
+    /* Set page range */
 	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_PAGE_RANGE);
 	if (ret < 0)
 		return ret;
@@ -427,18 +431,28 @@ static int ssd1307fb_ssd1306_init(struct ssd1307fb_par *par)
 	return 0;
 }
 
-static struct ssd1307fb_ops ssd1307fb_ssd1306_ops = {
-	.init	= ssd1307fb_ssd1306_init,
+static struct ssd1307fb_deviceinfo ssd1307fb_ssd1306_deviceinfo = {
+	.device_id  = DEVID_SSD1306,
+	.default_vcomh = 0x20,
+	.default_dclk_div = 0,
+	.default_dclk_frq = 8,
+};
+
+static struct ssd1307fb_deviceinfo ssd1307fb_ssd1307_deviceinfo = {
+	.device_id  = DEVID_SSD1307,
+	.default_vcomh = 0x20,
+	.default_dclk_div = 1,
+	.default_dclk_frq = 12,
 };
 
 static const struct of_device_id ssd1307fb_of_match[] = {
 	{
 		.compatible = "solomon,ssd1306fb-i2c",
-		.data = (void *)&ssd1307fb_ssd1306_ops,
+		.data = (void *)&ssd1307fb_ssd1306_deviceinfo,
 	},
 	{
 		.compatible = "solomon,ssd1307fb-i2c",
-		.data = (void *)&ssd1307fb_ssd1307_ops,
+		.data = (void *)&ssd1307fb_ssd1307_deviceinfo,
 	},
 	{},
 };
@@ -469,8 +483,8 @@ static int ssd1307fb_probe(struct i2c_client *client,
 	par->info = info;
 	par->client = client;
 
-	par->ops = (struct ssd1307fb_ops *)of_match_device(ssd1307fb_of_match,
-							   &client->dev)->data;
+	par->device_info = (struct ssd1307fb_deviceinfo *)of_match_device(
+			ssd1307fb_of_match, &client->dev)->data;
 
 	par->reset = of_get_named_gpio(client->dev.of_node,
 					 "reset-gpios", 0);
@@ -488,6 +502,27 @@ static int ssd1307fb_probe(struct i2c_client *client,
 	if (of_property_read_u32(node, "solomon,page-offset", &par->page_offset))
 		par->page_offset = 1;
 
+	if (of_property_read_u32(node, "solomon,com-offset", &par->com_offset))
+		par->com_offset = 0;
+
+	if (of_property_read_u32(node, "solomon,prechargep1", &par->prechargep1))
+		par->prechargep1 = 2;
+
+	if (of_property_read_u32(node, "solomon,prechargep2", &par->prechargep2))
+		par->prechargep2 = 0;
+
+	par->seg_remap = of_property_read_bool(node, "solomon,segment-remap");
+	par->com_seq = of_property_read_bool(node, "solomon,com-sequential");
+	par->com_lrremap = of_property_read_bool(node, "solomon,com-lrremap");
+	par->com_invdir = of_property_read_bool(node, "solomon,com-invdir");
+
+	par->contrast = contrast;
+	par->vcomh = par->device_info->default_vcomh;
+
+	/* Setup display timing */
+	par->dclk_div = par->device_info->default_dclk_div;
+	par->dclk_frq = par->device_info->default_dclk_frq;
+
 	vmem_size = par->width * par->height / 8;
 
 	vmem = vzalloc(vmem_size);
@@ -539,11 +574,9 @@ static int ssd1307fb_probe(struct i2c_client *client,
 	gpio_set_value(par->reset, 1);
 	udelay(4);
 
-	if (par->ops->init) {
-		ret = par->ops->init(par);
-		if (ret)
-			goto reset_oled_error;
-	}
+	ret = ssd1307fb_init(par);
+	if (ret)
+		goto reset_oled_error;
 
 	ret = register_framebuffer(info);
 	if (ret) {
@@ -556,8 +589,10 @@ static int ssd1307fb_probe(struct i2c_client *client,
 	return 0;
 
 panel_init_error:
-	if (par->ops->remove)
-		par->ops->remove(par);
+	if (par->device_info->device_id == DEVID_SSD1307) {
+		pwm_disable(par->pwm);
+		pwm_put(par->pwm);
+	};
 reset_oled_error:
 	fb_deferred_io_cleanup(info);
 	vfree(vmem);
@@ -572,8 +607,10 @@ static int ssd1307fb_remove(struct i2c_client *client)
 	struct ssd1307fb_par *par = info->par;
 
 	unregister_framebuffer(info);
-	if (par->ops->remove)
-		par->ops->remove(par);
+	if (par->device_info->device_id == DEVID_SSD1307) {
+		pwm_disable(par->pwm);
+		pwm_put(par->pwm);
+	};
 	fb_deferred_io_cleanup(info);
 	framebuffer_release(info);
 
-- 
2.3.0