btext.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Procedures for drawing on the screen early on in the boot process.
 *
 * Benjamin Herrenschmidt <[email protected]>
 */
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/font.h>

#include <asm/btext.h>
#include <asm/oplib.h>
#include <asm/io.h>

#define NO_SCROLL

#ifndef NO_SCROLL
static void scrollscreen(void);
#endif

static void draw_byte(unsigned char c, long locX, long locY);
static void draw_byte_32(const unsigned char *bits, unsigned int *base, int rb);
static void draw_byte_16(const unsigned char *bits, unsigned int *base, int rb);
static void draw_byte_8(const unsigned char *bits, unsigned int *base, int rb);

#define __force_data __section(".data")

static int g_loc_X __force_data;
static int g_loc_Y __force_data;
static int g_max_loc_X __force_data;
static int g_max_loc_Y __force_data;

static int dispDeviceRowBytes __force_data;
static int dispDeviceDepth  __force_data;
static int dispDeviceRect[4] __force_data;
static unsigned char *dispDeviceBase __force_data;

static int __init btext_initialize(phandle node)
{
	unsigned int width, height, depth, pitch;
	unsigned long address = 0;
	u32 prop;

	if (prom_getproperty(node, "width", (char *)&width, 4) < 0)
		return -EINVAL;
	if (prom_getproperty(node, "height", (char *)&height, 4) < 0)
		return -EINVAL;
	if (prom_getproperty(node, "depth", (char *)&depth, 4) < 0)
		return -EINVAL;
	pitch = width * ((depth + 7) / 8);

	if (prom_getproperty(node, "linebytes", (char *)&prop, 4) >= 0 &&
	    prop != 0xffffffffu)
		pitch = prop;

	if (pitch == 1)
		pitch = 0x1000;

	if (prom_getproperty(node, "address", (char *)&prop, 4) >= 0)
		address = prop;

	/* FIXME: Add support for PCI reg properties. Right now, only
	 * reliable on macs
	 */
	if (address == 0)
		return -EINVAL;

	g_loc_X = 0;
	g_loc_Y = 0;
	g_max_loc_X = width / 8;
	g_max_loc_Y = height / 16;
	dispDeviceBase = (unsigned char *)address;
	dispDeviceRowBytes = pitch;
	dispDeviceDepth = depth == 15 ? 16 : depth;
	dispDeviceRect[0] = dispDeviceRect[1] = 0;
	dispDeviceRect[2] = width;
	dispDeviceRect[3] = height;

	return 0;
}

/* Calc the base address of a given point (x,y) */
static unsigned char * calc_base(int x, int y)
{
	unsigned char *base = dispDeviceBase;

	base += (x + dispDeviceRect[0]) * (dispDeviceDepth >> 3);
	base += (y + dispDeviceRect[1]) * dispDeviceRowBytes;
	return base;
}

static void btext_clearscreen(void)
{
	unsigned int *base	= (unsigned int *)calc_base(0, 0);
	unsigned long width 	= ((dispDeviceRect[2] - dispDeviceRect[0]) *
					(dispDeviceDepth >> 3)) >> 2;
	int i,j;

	for (i=0; i<(dispDeviceRect[3] - dispDeviceRect[1]); i++)
	{
		unsigned int *ptr = base;
		for(j=width; j; --j)
			*(ptr++) = 0;
		base += (dispDeviceRowBytes >> 2);
	}
}

#ifndef NO_SCROLL
static void scrollscreen(void)
{
	unsigned int *src     	= (unsigned int *)calc_base(0,16);
	unsigned int *dst     	= (unsigned int *)calc_base(0,0);
	unsigned long width    	= ((dispDeviceRect[2] - dispDeviceRect[0]) *
				   (dispDeviceDepth >> 3)) >> 2;
	int i,j;

	for (i=0; i<(dispDeviceRect[3] - dispDeviceRect[1] - 16); i++)
	{
		unsigned int *src_ptr = src;
		unsigned int *dst_ptr = dst;
		for(j=width; j; --j)
			*(dst_ptr++) = *(src_ptr++);
		src += (dispDeviceRowBytes >> 2);
		dst += (dispDeviceRowBytes >> 2);
	}
	for (i=0; i<16; i++)
	{
		unsigned int *dst_ptr = dst;
		for(j=width; j; --j)
			*(dst_ptr++) = 0;
		dst += (dispDeviceRowBytes >> 2);
	}
}
#endif /* ndef NO_SCROLL */

static void btext_drawchar(char c)
{
	int cline = 0;
#ifdef NO_SCROLL
	int x;
#endif
	switch (c) {
	case '\b':
		if (g_loc_X > 0)
			--g_loc_X;
		break;
	case '\t':
		g_loc_X = (g_loc_X & -8) + 8;
		break;
	case '\r':
		g_loc_X = 0;
		break;
	case '\n':
		g_loc_X = 0;
		g_loc_Y++;
		cline = 1;
		break;
	default:
		draw_byte(c, g_loc_X++, g_loc_Y);
	}
	if (g_loc_X >= g_max_loc_X) {
		g_loc_X = 0;
		g_loc_Y++;
		cline = 1;
	}
#ifndef NO_SCROLL
	while (g_loc_Y >= g_max_loc_Y) {
		scrollscreen();
		g_loc_Y--;
	}
#else
	/* wrap around from bottom to top of screen so we don't
	   waste time scrolling each line.  -- paulus. */
	if (g_loc_Y >= g_max_loc_Y)
		g_loc_Y = 0;
	if (cline) {
		for (x = 0; x < g_max_loc_X; ++x)
			draw_byte(' ', x, g_loc_Y);
	}
#endif
}

static void btext_drawtext(const char *c, unsigned int len)
{
	while (len--)
		btext_drawchar(*c++);
}

static void draw_byte(unsigned char c, long locX, long locY)
{
	unsigned char *base	= calc_base(locX << 3, locY << 4);
	unsigned int font_index = c * 16;
	const unsigned char *font	= font_sun_8x16.data + font_index;
	int rb			= dispDeviceRowBytes;

	switch(dispDeviceDepth) {
	case 24:
	case 32:
		draw_byte_32(font, (unsigned int *)base, rb);
		break;
	case 15:
	case 16:
		draw_byte_16(font, (unsigned int *)base, rb);
		break;
	case 8:
		draw_byte_8(font, (unsigned int *)base, rb);
		break;
	}
}

static unsigned int expand_bits_8[16] = {
	0x00000000,
	0x000000ff,
	0x0000ff00,
	0x0000ffff,
	0x00ff0000,
	0x00ff00ff,
	0x00ffff00,
	0x00ffffff,
	0xff000000,
	0xff0000ff,
	0xff00ff00,
	0xff00ffff,
	0xffff0000,
	0xffff00ff,
	0xffffff00,
	0xffffffff
};

static unsigned int expand_bits_16[4] = {
	0x00000000,
	0x0000ffff,
	0xffff0000,
	0xffffffff
};


static void draw_byte_32(const unsigned char *font, unsigned int *base, int rb)
{
	int l, bits;
	int fg = 0xFFFFFFFFUL;
	int bg = 0x00000000UL;

	for (l = 0; l < 16; ++l)
	{
		bits = *font++;
		base[0] = (-(bits >> 7) & fg) ^ bg;
		base[1] = (-((bits >> 6) & 1) & fg) ^ bg;
		base[2] = (-((bits >> 5) & 1) & fg) ^ bg;
		base[3] = (-((bits >> 4) & 1) & fg) ^ bg;
		base[4] = (-((bits >> 3) & 1) & fg) ^ bg;
		base[5] = (-((bits >> 2) & 1) & fg) ^ bg;
		base[6] = (-((bits >> 1) & 1) & fg) ^ bg;
		base[7] = (-(bits & 1) & fg) ^ bg;
		base = (unsigned int *) ((char *)base + rb);
	}
}

static void draw_byte_16(const unsigned char *font, unsigned int *base, int rb)
{
	int l, bits;
	int fg = 0xFFFFFFFFUL;
	int bg = 0x00000000UL;
	unsigned int *eb = (int *)expand_bits_16;

	for (l = 0; l < 16; ++l)
	{
		bits = *font++;
		base[0] = (eb[bits >> 6] & fg) ^ bg;
		base[1] = (eb[(bits >> 4) & 3] & fg) ^ bg;
		base[2] = (eb[(bits >> 2) & 3] & fg) ^ bg;
		base[3] = (eb[bits & 3] & fg) ^ bg;
		base = (unsigned int *) ((char *)base + rb);
	}
}

static void draw_byte_8(const unsigned char *font, unsigned int *base, int rb)
{
	int l, bits;
	int fg = 0x0F0F0F0FUL;
	int bg = 0x00000000UL;
	unsigned int *eb = (int *)expand_bits_8;

	for (l = 0; l < 16; ++l)
	{
		bits = *font++;
		base[0] = (eb[bits >> 4] & fg) ^ bg;
		base[1] = (eb[bits & 0xf] & fg) ^ bg;
		base = (unsigned int *) ((char *)base + rb);
	}
}

static void btext_console_write(struct console *con, const char *s,
				unsigned int n)
{
	btext_drawtext(s, n);
}

static struct console btext_console = {
	.name	= "btext",
	.write	= btext_console_write,
	.flags	= CON_PRINTBUFFER | CON_ENABLED | CON_BOOT | CON_ANYTIME,
	.index	= 0,
};

int __init btext_find_display(void)
{
	phandle node;
	char type[32];
	int ret;

	node = prom_inst2pkg(prom_stdout);
	if (prom_getproperty(node, "device_type", type, 32) < 0)
		return -ENODEV;
	if (strcmp(type, "display"))
		return -ENODEV;

	ret = btext_initialize(node);
	if (!ret) {
		btext_clearscreen();
		register_console(&btext_console);
	}
	return ret;
}