staging: fbtft: add fb_ssd1306 driver

This commit adds the fb_ssd1306 driver from the fbtft project at
https://github.com/notro/fbtft.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Noralf Tronnes <notro@tronnes.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fbtft/Kconfig

@@ -103,3 +103,9 @@ config FB_TFT_SSD1289
 	depends on FB_TFT
 	help
 	  Framebuffer support for SSD1289
+
+config FB_TFT_SSD1306
+	tristate "FB driver for the SSD1306 OLED Controller"
+	depends on FB_TFT
+	help
+	  Framebuffer support for SSD1306

drivers/staging/fbtft/Makefile

@@ -19,3 +19,4 @@ obj-$(CONFIG_FB_TFT_RA8875)      += fb_ra8875.o
 obj-$(CONFIG_FB_TFT_S6D02A1)     += fb_s6d02a1.o
 obj-$(CONFIG_FB_TFT_S6D1121)     += fb_s6d1121.o
 obj-$(CONFIG_FB_TFT_SSD1289)     += fb_ssd1289.o
+obj-$(CONFIG_FB_TFT_SSD1306)     += fb_ssd1306.o

drivers/staging/fbtft/fb_ssd1306.c

+/*
+ * FB driver for the SSD1306 OLED Controller
+ *
+ * Copyright (C) 2013 Noralf Tronnes
+ *
+ * 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
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/gpio.h>
+#include <linux/delay.h>
+
+#include "fbtft.h"
+
+#define DRVNAME		"fb_ssd1306"
+#define WIDTH		128
+#define HEIGHT		64
+
+
+/*
+  write_reg() caveat:
+
+     This doesn't work because D/C has to be LOW for both values:
+       write_reg(par, val1, val2);
+
+     Do it like this:
+       write_reg(par, val1);
+       write_reg(par, val2);
+*/
+
+/* Init sequence taken from the Adafruit SSD1306 Arduino library */
+static int init_display(struct fbtft_par *par)
+{
+	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);
+
+	par->fbtftops.reset(par);
+
+	if (par->gamma.curves[0] == 0) {
+		mutex_lock(&par->gamma.lock);
+		if (par->info->var.yres == 64)
+			par->gamma.curves[0] = 0xCF;
+		else
+			par->gamma.curves[0] = 0x8F;
+		mutex_unlock(&par->gamma.lock);
+	}
+
+	/* Set Display OFF */
+	write_reg(par, 0xAE);
+
+	/* Set Display Clock Divide Ratio/ Oscillator Frequency */
+	write_reg(par, 0xD5);
+	write_reg(par, 0x80);
+
+	/* Set Multiplex Ratio */
+	write_reg(par, 0xA8);
+	if (par->info->var.yres == 64)
+		write_reg(par, 0x3F);
+	else
+		write_reg(par, 0x1F);
+
+	/* Set Display Offset */
+	write_reg(par, 0xD3);
+	write_reg(par, 0x0);
+
+	/* Set Display Start Line */
+	write_reg(par, 0x40 | 0x0);
+
+	/* Charge Pump Setting */
+	write_reg(par, 0x8D);
+	/* A[2] = 1b, Enable charge pump during display on */
+	write_reg(par, 0x14);
+
+	/* Set Memory Addressing Mode */
+	write_reg(par, 0x20);
+	/* Vertical addressing mode  */
+	write_reg(par, 0x01);
+
+	/*Set Segment Re-map */
+	/* column address 127 is mapped to SEG0 */
+	write_reg(par, 0xA0 | 0x1);
+
+	/* Set COM Output Scan Direction */
+	/* remapped mode. Scan from COM[N-1] to COM0 */
+	write_reg(par, 0xC8);
+
+	/* Set COM Pins Hardware Configuration */
+	write_reg(par, 0xDA);
+	if (par->info->var.yres == 64)
+		/* A[4]=1b, Alternative COM pin configuration */
+		write_reg(par, 0x12);
+	else
+		/* A[4]=0b, Sequential COM pin configuration */
+		write_reg(par, 0x02);
+
+	/* Set Pre-charge Period */
+	write_reg(par, 0xD9);
+	write_reg(par, 0xF1);
+
+	/* Set VCOMH Deselect Level */
+	write_reg(par, 0xDB);
+	/* according to the datasheet, this value is out of bounds */
+	write_reg(par, 0x40);
+
+	/* Entire Display ON */
+	/* Resume to RAM content display. Output follows RAM content */
+	write_reg(par, 0xA4);
+
+	/* Set Normal Display
+	   0 in RAM: OFF in display panel
+	   1 in RAM: ON in display panel */
+	write_reg(par, 0xA6);
+
+	/* Set Display ON */
+	write_reg(par, 0xAF);
+
+	return 0;
+}
+
+static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
+{
+	fbtft_par_dbg(DEBUG_SET_ADDR_WIN, par,
+		"%s(xs=%d, ys=%d, xe=%d, ye=%d)\n", __func__, xs, ys, xe, ye);
+
+	/* Set Lower Column Start Address for Page Addressing Mode */
+	write_reg(par, 0x00 | 0x0);
+	/* Set Higher Column Start Address for Page Addressing Mode */
+	write_reg(par, 0x10 | 0x0);
+	/* Set Display Start Line */
+	write_reg(par, 0x40 | 0x0);
+}
+
+static int blank(struct fbtft_par *par, bool on)
+{
+	fbtft_par_dbg(DEBUG_BLANK, par, "%s(blank=%s)\n",
+		__func__, on ? "true" : "false");
+
+	if (on)
+		write_reg(par, 0xAE);
+	else
+		write_reg(par, 0xAF);
+	return 0;
+}
+
+/* Gamma is used to control Contrast */
+static int set_gamma(struct fbtft_par *par, unsigned long *curves)
+{
+	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);
+
+	/* apply mask */
+	curves[0] &= 0xFF;
+
+	/* Set Contrast Control for BANK0 */
+	write_reg(par, 0x81);
+	write_reg(par, curves[0]);
+
+	return 0;
+}
+
+static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
+{
+	u16 *vmem16 = (u16 *)par->info->screen_base;
+	u8 *buf = par->txbuf.buf;
+	int x, y, i;
+	int ret = 0;
+
+	fbtft_par_dbg(DEBUG_WRITE_VMEM, par, "%s()\n", __func__);
+
+	for (x = 0; x < par->info->var.xres; x++) {
+		for (y = 0; y < par->info->var.yres/8; y++) {
+			*buf = 0x00;
+			for (i = 0; i < 8; i++)
+				*buf |= (vmem16[(y*8+i)*par->info->var.xres+x] ? 1 : 0) << i;
+			buf++;
+		}
+	}
+
+	/* Write data */
+	gpio_set_value(par->gpio.dc, 1);
+	ret = par->fbtftops.write(par, par->txbuf.buf,
+				par->info->var.xres*par->info->var.yres/8);
+	if (ret < 0)
+		dev_err(par->info->device,
+			"%s: write failed and returned: %d\n", __func__, ret);
+
+	return ret;
+}
+
+
+static struct fbtft_display display = {
+	.regwidth = 8,
+	.width = WIDTH,
+	.height = HEIGHT,
+	.gamma_num = 1,
+	.gamma_len = 1,
+	.gamma = "00",
+	.fbtftops = {
+		.write_vmem = write_vmem,
+		.init_display = init_display,
+		.set_addr_win = set_addr_win,
+		.blank = blank,
+		.set_gamma = set_gamma,
+	},
+};
+
+
+FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1306", &display);
+
+MODULE_ALIAS("spi:" DRVNAME);
+MODULE_ALIAS("platform:" DRVNAME);
+MODULE_ALIAS("spi:ssd1306");
+MODULE_ALIAS("platform:ssd1306");
+
+MODULE_DESCRIPTION("SSD1306 OLED Driver");
+MODULE_AUTHOR("Noralf Tronnes");
+MODULE_LICENSE("GPL");