midgard/r12p0/kernel/drivers/gpu/drm/pl111/pl111_drm_cursor.c - manifest_repos/mali-driver - Git at Google

 /*
  *
  * (C) COPYRIGHT 2012-2013 ARM Limited. All rights reserved.
  *
  * This program is free software and is provided to you under the terms of the
  * GNU General Public License version 2 as published by the Free Software
  * Foundation, and any use by you of this program is subject to the terms
  * of such GNU licence.
  *
  * A copy of the licence is included with the program, and can also be obtained
  * from Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA  02110-1301, USA.
  *
  */


 /**
  * pl111_drm_cursor.c
  * Implementation of cursor functions for PL111 DRM
  */
 #include <linux/amba/bus.h>
 #include <linux/amba/clcd.h>
 #include <linux/version.h>
 #include <linux/shmem_fs.h>
 #include <linux/dma-buf.h>
 #include <linux/module.h>

 #include <drm/drmP.h>
 #include <drm/drm_crtc_helper.h>
 #include "pl111_clcd_ext.h"
 #include "pl111_drm.h"

 #define PL111_MAX_CURSOR_WIDTH (64)
 #define PL111_MAX_CURSOR_HEIGHT (64)

 #define ARGB_2_LBBP_BINARY_THRESHOLD	(1 << 7)
 #define ARGB_ALPHA_SHIFT		24
 #define ARGB_ALPHA_MASK			(0xff << ARGB_ALPHA_SHIFT)
 #define ARGB_RED_SHIFT			16
 #define ARGB_RED_MASK			(0xff << ARGB_RED_SHIFT)
 #define ARGB_GREEN_SHIFT		8
 #define ARGB_GREEN_MASK			(0xff << ARGB_GREEN_SHIFT)
 #define ARGB_BLUE_SHIFT			0
 #define ARGB_BLUE_MASK			(0xff << ARGB_BLUE_SHIFT)


 void pl111_set_cursor_size(enum pl111_cursor_size size)
 {
 	u32 reg_data = readl(priv.regs + CLCD_CRSR_CONFIG);

 	if (size == CURSOR_64X64)
 		reg_data |= CRSR_CONFIG_CRSR_SIZE;
 	else
 		reg_data &= ~CRSR_CONFIG_CRSR_SIZE;

 	writel(reg_data, priv.regs + CLCD_CRSR_CONFIG);
 }

 void pl111_set_cursor_sync(enum pl111_cursor_sync sync)
 {
 	u32 reg_data = readl(priv.regs + CLCD_CRSR_CONFIG);

 	if (sync == CURSOR_SYNC_VSYNC)
 		reg_data |= CRSR_CONFIG_CRSR_FRAME_SYNC;
 	else
 		reg_data &= ~CRSR_CONFIG_CRSR_FRAME_SYNC;

 	writel(reg_data, priv.regs + CLCD_CRSR_CONFIG);
 }

 void pl111_set_cursor(u32 cursor)
 {
 	u32 reg_data = readl(priv.regs + CLCD_CRSR_CTRL);

 	reg_data &= ~(CRSR_CTRL_CRSR_MAX << CRSR_CTRL_CRSR_NUM_SHIFT);
 	reg_data |= (cursor & CRSR_CTRL_CRSR_MAX) << CRSR_CTRL_CRSR_NUM_SHIFT;

 	writel(reg_data, priv.regs + CLCD_CRSR_CTRL);
 }

 void pl111_set_cursor_enable(bool enable)
 {
 	u32 reg_data = readl(priv.regs + CLCD_CRSR_CTRL);

 	if (enable)
 		reg_data |= CRSR_CTRL_CRSR_ON;
 	else
 		reg_data &= ~CRSR_CTRL_CRSR_ON;

 	writel(reg_data, priv.regs + CLCD_CRSR_CTRL);
 }

 void pl111_set_cursor_position(u32 x, u32 y)
 {
 	u32 reg_data = (x & CRSR_XY_MASK) |
 			((y & CRSR_XY_MASK) << CRSR_XY_Y_SHIFT);

 	writel(reg_data, priv.regs + CLCD_CRSR_XY);
 }

 void pl111_set_cursor_clipping(u32 x, u32 y)
 {
 	u32 reg_data;

 	/*
 	 * Do not allow setting clipping values larger than
 	 * the cursor size since the cursor is already fully hidden
 	 * when x,y = PL111_MAX_CURSOR_WIDTH.
 	 */
 	if (x > PL111_MAX_CURSOR_WIDTH)
 		x = PL111_MAX_CURSOR_WIDTH;
 	if (y > PL111_MAX_CURSOR_WIDTH)
 		y = PL111_MAX_CURSOR_WIDTH;

 	reg_data = (x & CRSR_CLIP_MASK) |
 			((y & CRSR_CLIP_MASK) << CRSR_CLIP_Y_SHIFT);

 	writel(reg_data, priv.regs + CLCD_CRSR_CLIP);
 }

 void pl111_set_cursor_palette(u32 color0, u32 color1)
 {
 	writel(color0 & CRSR_PALETTE_MASK, priv.regs + CLCD_CRSR_PALETTE_0);
 	writel(color1 & CRSR_PALETTE_MASK, priv.regs + CLCD_CRSR_PALETTE_1);
 }

 void pl111_cursor_enable(void)
 {
 	pl111_set_cursor_sync(CURSOR_SYNC_VSYNC);
 	pl111_set_cursor_size(CURSOR_64X64);
 	pl111_set_cursor_palette(0x0, 0x00ffffff);
 	pl111_set_cursor_enable(true);
 }

 void pl111_cursor_disable(void)
 {
 	pl111_set_cursor_enable(false);
 }

 /* shift required to locate pixel into the correct position in
  * a cursor LBBP word, indexed by x mod 16.
  */
 static const unsigned char
 x_mod_16_to_value_shift[CLCD_CRSR_IMAGE_PIXELS_PER_WORD] = {
 	6, 4, 2, 0, 14, 12, 10, 8, 22, 20, 18, 16, 30, 28, 26, 24
 };

 /* Pack the pixel value into its correct position in the buffer as specified
  * for LBBP */
 static inline void
 set_lbbp_pixel(uint32_t *buffer, unsigned int x, unsigned int y,
 				uint32_t value)
 {
 	u32 *cursor_ram = priv.regs + CLCD_CRSR_IMAGE;
 	uint32_t shift;
 	uint32_t data;

 	shift = x_mod_16_to_value_shift[x % CLCD_CRSR_IMAGE_PIXELS_PER_WORD];

 	/* Get the word containing this pixel */
 	cursor_ram = cursor_ram + (x >> CLCD_CRSR_IMAGE_WORDS_PER_LINE) + (y << 2);

 	/* Update pixel in cursor RAM */
 	data = readl(cursor_ram);
 	data &= ~(CLCD_CRSR_LBBP_COLOR_MASK << shift);
 	data |= value << shift;
 	writel(data, cursor_ram);
 }

 static u32 pl111_argb_to_lbbp(u32 argb_pix)
 {
 	u32 lbbp_pix = CLCD_CRSR_LBBP_TRANSPARENT;
 	u32 alpha = (argb_pix & ARGB_ALPHA_MASK) >> ARGB_ALPHA_SHIFT;
 	u32 red = (argb_pix & ARGB_RED_MASK) >> ARGB_RED_SHIFT;
 	u32 green = (argb_pix & ARGB_GREEN_MASK) >> ARGB_GREEN_SHIFT;
 	u32 blue =  (argb_pix & ARGB_BLUE_MASK) >> ARGB_BLUE_SHIFT;

 	/*
 	 * Converting from 8 pixel transparency to binary transparency
 	 * it's the best we can achieve.
 	 */
 	if (alpha & ARGB_2_LBBP_BINARY_THRESHOLD) {
 		u32 gray, max, min;

 		/*
 		 * Convert to gray using the lightness method:
 		 * gray = [max(R,G,B) + min(R,G,B)]/2
 		 */
 		min = min(red, green);
 		min = min(min, blue);
 		max = max(red, green);
 		max = max(max, blue);
 		gray = (min + max) >> 1; /* divide by 2 */
 		/* Apply binary threshold to the gray value calculated */
 		if (gray & ARGB_2_LBBP_BINARY_THRESHOLD)
 			lbbp_pix = CLCD_CRSR_LBBP_FOREGROUND;
 		else
 			lbbp_pix = CLCD_CRSR_LBBP_BACKGROUND;
 	}

 	return lbbp_pix;
 }

 /*
  * The PL111 hardware cursor supports only LBBP which is a 2bpp format but
  * the cursor format from userspace is ARGB8888 so we need to convert
  *  to LBBP here.
  */
 static void pl111_set_cursor_image(u32 *data)
 {
 #ifdef ARGB_LBBP_CONVERSION_DEBUG
 	/* Add 1 on width to insert trailing NULL */
 	char string_cursor[PL111_MAX_CURSOR_WIDTH + 1];
 #endif /* ARGB_LBBP_CONVERSION_DEBUG */
 	unsigned int x;
 	unsigned int y;

 	for (y = 0; y < PL111_MAX_CURSOR_HEIGHT; y++) {
 		for (x = 0; x < PL111_MAX_CURSOR_WIDTH; x++) {
 			u32 value = pl111_argb_to_lbbp(*data);

 #ifdef ARGB_LBBP_CONVERSION_DEBUG
 			if (value == CLCD_CRSR_LBBP_TRANSPARENT)
 				string_cursor[x] = 'T';
 			else if (value == CLCD_CRSR_LBBP_FOREGROUND)
 				string_cursor[x] = 'F';
 			else if (value == CLCD_CRSR_LBBP_INVERSE)
 				string_cursor[x] = 'I';
 			else
 				string_cursor[x] = 'B';

 #endif /* ARGB_LBBP_CONVERSION_DEBUG */
 			set_lbbp_pixel(data, x, y, value);
 			++data;
 		}
 #ifdef ARGB_LBBP_CONVERSION_DEBUG
 		string_cursor[PL111_MAX_CURSOR_WIDTH] = '\0';
 		DRM_INFO("%s\n", string_cursor);
 #endif /* ARGB_LBBP_CONVERSION_DEBUG */
 	}
 }

 int pl111_crtc_cursor_set(struct drm_crtc *crtc,
 			   struct drm_file *file_priv,
 			   uint32_t handle,
 			   uint32_t width,
 			   uint32_t height)
 {
 	struct drm_gem_object *obj;
 	struct pl111_gem_bo *bo;

 	DRM_DEBUG_KMS("handle = %u, width = %u, height = %u\n",
 		handle, width, height);

 	if (!handle) {
 		pl111_cursor_disable();
 		return 0;
 	}

 	if ((width != PL111_MAX_CURSOR_WIDTH) ||
 	    (height != PL111_MAX_CURSOR_HEIGHT))
 		return -EINVAL;

 	obj = drm_gem_object_lookup(crtc->dev, file_priv, handle);
 	if (!obj) {
 		DRM_ERROR("Cannot find cursor object for handle = %d\n",
 			  handle);
 		return -ENOENT;
 	}

 	/*
 	 * We expect a PL111_MAX_CURSOR_WIDTH x PL111_MAX_CURSOR_HEIGHT
 	 * ARGB888 buffer object in the input.
 	 *
 	 */
 	if (obj->size < (PL111_MAX_CURSOR_WIDTH * PL111_MAX_CURSOR_HEIGHT * 4)) {
 		DRM_ERROR("Cannot set cursor with an obj size = %d\n",
 			  obj->size);
 		drm_gem_object_unreference_unlocked(obj);
 		return -EINVAL;
 	}

 	bo = PL111_BO_FROM_GEM(obj);
 	if (!(bo->type & PL111_BOT_DMA)) {
 		DRM_ERROR("Tried to set cursor with non DMA backed obj = %p\n",
 			  obj);
 		drm_gem_object_unreference_unlocked(obj);
 		return -EINVAL;
 	}

 	pl111_set_cursor_image(bo->backing_data.dma.fb_cpu_addr);

 	/*
 	 * Since we copy the contents of the buffer to the HW cursor internal
 	 * memory this GEM object is not needed anymore.
 	 */
 	drm_gem_object_unreference_unlocked(obj);

 	pl111_cursor_enable();

 	return 0;
 }

 int pl111_crtc_cursor_move(struct drm_crtc *crtc,
 			    int x, int y)
 {
 	int x_clip = 0;
 	int y_clip = 0;

 	DRM_DEBUG("x %d y %d\n", x, y);

 	/*
 	 * The cursor image is clipped automatically at the screen limits when
 	 * it extends beyond the screen image to the right or bottom but
 	 * we must clip it using pl111 HW features for negative values.
 	 */
 	if (x < 0) {
 		x_clip = -x;
 		x = 0;
 	}
 	if (y < 0) {
 		y_clip = -y;
 		y = 0;
 	}

 	pl111_set_cursor_clipping(x_clip, y_clip);
 	pl111_set_cursor_position(x, y);

 	return 0;
 }
	/*
	*
	* (C) COPYRIGHT 2012-2013 ARM Limited. All rights reserved.
	*
	* This program is free software and is provided to you under the terms of the
	* GNU General Public License version 2 as published by the Free Software
	* Foundation, and any use by you of this program is subject to the terms
	* of such GNU licence.
	*
	* A copy of the licence is included with the program, and can also be obtained
	* from Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
	* Boston, MA 02110-1301, USA.
	*
	*/



	/**
	* pl111_drm_cursor.c
	* Implementation of cursor functions for PL111 DRM
	*/
	#include <linux/amba/bus.h>
	#include <linux/amba/clcd.h>
	#include <linux/version.h>
	#include <linux/shmem_fs.h>
	#include <linux/dma-buf.h>
	#include <linux/module.h>

	#include <drm/drmP.h>
	#include <drm/drm_crtc_helper.h>
	#include "pl111_clcd_ext.h"
	#include "pl111_drm.h"

	#define PL111_MAX_CURSOR_WIDTH (64)
	#define PL111_MAX_CURSOR_HEIGHT (64)

	#define ARGB_2_LBBP_BINARY_THRESHOLD (1 << 7)
	#define ARGB_ALPHA_SHIFT 24
	#define ARGB_ALPHA_MASK (0xff << ARGB_ALPHA_SHIFT)
	#define ARGB_RED_SHIFT 16
	#define ARGB_RED_MASK (0xff << ARGB_RED_SHIFT)
	#define ARGB_GREEN_SHIFT 8
	#define ARGB_GREEN_MASK (0xff << ARGB_GREEN_SHIFT)
	#define ARGB_BLUE_SHIFT 0
	#define ARGB_BLUE_MASK (0xff << ARGB_BLUE_SHIFT)


	void pl111_set_cursor_size(enum pl111_cursor_size size)
	{
	u32 reg_data = readl(priv.regs + CLCD_CRSR_CONFIG);

	if (size == CURSOR_64X64)
	reg_data \|= CRSR_CONFIG_CRSR_SIZE;
	else
	reg_data &= ~CRSR_CONFIG_CRSR_SIZE;

	writel(reg_data, priv.regs + CLCD_CRSR_CONFIG);
	}

	void pl111_set_cursor_sync(enum pl111_cursor_sync sync)
	{
	u32 reg_data = readl(priv.regs + CLCD_CRSR_CONFIG);

	if (sync == CURSOR_SYNC_VSYNC)
	reg_data \|= CRSR_CONFIG_CRSR_FRAME_SYNC;
	else
	reg_data &= ~CRSR_CONFIG_CRSR_FRAME_SYNC;

	writel(reg_data, priv.regs + CLCD_CRSR_CONFIG);
	}

	void pl111_set_cursor(u32 cursor)
	{
	u32 reg_data = readl(priv.regs + CLCD_CRSR_CTRL);

	reg_data &= ~(CRSR_CTRL_CRSR_MAX << CRSR_CTRL_CRSR_NUM_SHIFT);
	reg_data \|= (cursor & CRSR_CTRL_CRSR_MAX) << CRSR_CTRL_CRSR_NUM_SHIFT;

	writel(reg_data, priv.regs + CLCD_CRSR_CTRL);
	}

	void pl111_set_cursor_enable(bool enable)
	{
	u32 reg_data = readl(priv.regs + CLCD_CRSR_CTRL);

	if (enable)
	reg_data \|= CRSR_CTRL_CRSR_ON;
	else
	reg_data &= ~CRSR_CTRL_CRSR_ON;

	writel(reg_data, priv.regs + CLCD_CRSR_CTRL);
	}

	void pl111_set_cursor_position(u32 x, u32 y)
	{
	u32 reg_data = (x & CRSR_XY_MASK) \|
	((y & CRSR_XY_MASK) << CRSR_XY_Y_SHIFT);

	writel(reg_data, priv.regs + CLCD_CRSR_XY);
	}

	void pl111_set_cursor_clipping(u32 x, u32 y)
	{
	u32 reg_data;

	/*
	* Do not allow setting clipping values larger than
	* the cursor size since the cursor is already fully hidden
	* when x,y = PL111_MAX_CURSOR_WIDTH.
	*/
	if (x > PL111_MAX_CURSOR_WIDTH)
	x = PL111_MAX_CURSOR_WIDTH;
	if (y > PL111_MAX_CURSOR_WIDTH)
	y = PL111_MAX_CURSOR_WIDTH;

	reg_data = (x & CRSR_CLIP_MASK) \|
	((y & CRSR_CLIP_MASK) << CRSR_CLIP_Y_SHIFT);

	writel(reg_data, priv.regs + CLCD_CRSR_CLIP);
	}

	void pl111_set_cursor_palette(u32 color0, u32 color1)
	{
	writel(color0 & CRSR_PALETTE_MASK, priv.regs + CLCD_CRSR_PALETTE_0);
	writel(color1 & CRSR_PALETTE_MASK, priv.regs + CLCD_CRSR_PALETTE_1);
	}

	void pl111_cursor_enable(void)
	{
	pl111_set_cursor_sync(CURSOR_SYNC_VSYNC);
	pl111_set_cursor_size(CURSOR_64X64);
	pl111_set_cursor_palette(0x0, 0x00ffffff);
	pl111_set_cursor_enable(true);
	}

	void pl111_cursor_disable(void)
	{
	pl111_set_cursor_enable(false);
	}

	/* shift required to locate pixel into the correct position in
	* a cursor LBBP word, indexed by x mod 16.
	*/
	static const unsigned char
	x_mod_16_to_value_shift[CLCD_CRSR_IMAGE_PIXELS_PER_WORD] = {
	6, 4, 2, 0, 14, 12, 10, 8, 22, 20, 18, 16, 30, 28, 26, 24
	};

	/* Pack the pixel value into its correct position in the buffer as specified
	* for LBBP */
	static inline void
	set_lbbp_pixel(uint32_t *buffer, unsigned int x, unsigned int y,
	uint32_t value)
	{
	u32 *cursor_ram = priv.regs + CLCD_CRSR_IMAGE;
	uint32_t shift;
	uint32_t data;

	shift = x_mod_16_to_value_shift[x % CLCD_CRSR_IMAGE_PIXELS_PER_WORD];

	/* Get the word containing this pixel */
	cursor_ram = cursor_ram + (x >> CLCD_CRSR_IMAGE_WORDS_PER_LINE) + (y << 2);

	/* Update pixel in cursor RAM */
	data = readl(cursor_ram);
	data &= ~(CLCD_CRSR_LBBP_COLOR_MASK << shift);
	data \|= value << shift;
	writel(data, cursor_ram);
	}

	static u32 pl111_argb_to_lbbp(u32 argb_pix)
	{
	u32 lbbp_pix = CLCD_CRSR_LBBP_TRANSPARENT;
	u32 alpha = (argb_pix & ARGB_ALPHA_MASK) >> ARGB_ALPHA_SHIFT;
	u32 red = (argb_pix & ARGB_RED_MASK) >> ARGB_RED_SHIFT;
	u32 green = (argb_pix & ARGB_GREEN_MASK) >> ARGB_GREEN_SHIFT;
	u32 blue = (argb_pix & ARGB_BLUE_MASK) >> ARGB_BLUE_SHIFT;

	/*
	* Converting from 8 pixel transparency to binary transparency
	* it's the best we can achieve.
	*/
	if (alpha & ARGB_2_LBBP_BINARY_THRESHOLD) {
	u32 gray, max, min;

	/*
	* Convert to gray using the lightness method:
	* gray = [max(R,G,B) + min(R,G,B)]/2
	*/
	min = min(red, green);
	min = min(min, blue);
	max = max(red, green);
	max = max(max, blue);
	gray = (min + max) >> 1; /* divide by 2 */
	/* Apply binary threshold to the gray value calculated */
	if (gray & ARGB_2_LBBP_BINARY_THRESHOLD)
	lbbp_pix = CLCD_CRSR_LBBP_FOREGROUND;
	else
	lbbp_pix = CLCD_CRSR_LBBP_BACKGROUND;
	}

	return lbbp_pix;
	}

	/*
	* The PL111 hardware cursor supports only LBBP which is a 2bpp format but
	* the cursor format from userspace is ARGB8888 so we need to convert
	* to LBBP here.
	*/
	static void pl111_set_cursor_image(u32 *data)
	{
	#ifdef ARGB_LBBP_CONVERSION_DEBUG
	/* Add 1 on width to insert trailing NULL */
	char string_cursor[PL111_MAX_CURSOR_WIDTH + 1];
	#endif /* ARGB_LBBP_CONVERSION_DEBUG */
	unsigned int x;
	unsigned int y;

	for (y = 0; y < PL111_MAX_CURSOR_HEIGHT; y++) {
	for (x = 0; x < PL111_MAX_CURSOR_WIDTH; x++) {
	u32 value = pl111_argb_to_lbbp(*data);

	#ifdef ARGB_LBBP_CONVERSION_DEBUG
	if (value == CLCD_CRSR_LBBP_TRANSPARENT)
	string_cursor[x] = 'T';
	else if (value == CLCD_CRSR_LBBP_FOREGROUND)
	string_cursor[x] = 'F';
	else if (value == CLCD_CRSR_LBBP_INVERSE)
	string_cursor[x] = 'I';
	else
	string_cursor[x] = 'B';

	#endif /* ARGB_LBBP_CONVERSION_DEBUG */
	set_lbbp_pixel(data, x, y, value);
	++data;
	}
	#ifdef ARGB_LBBP_CONVERSION_DEBUG
	string_cursor[PL111_MAX_CURSOR_WIDTH] = '\0';
	DRM_INFO("%s\n", string_cursor);
	#endif /* ARGB_LBBP_CONVERSION_DEBUG */
	}
	}

	int pl111_crtc_cursor_set(struct drm_crtc *crtc,
	struct drm_file *file_priv,
	uint32_t handle,
	uint32_t width,
	uint32_t height)
	{
	struct drm_gem_object *obj;
	struct pl111_gem_bo *bo;

	DRM_DEBUG_KMS("handle = %u, width = %u, height = %u\n",
	handle, width, height);

	if (!handle) {
	pl111_cursor_disable();
	return 0;
	}

	if ((width != PL111_MAX_CURSOR_WIDTH) \|\|
	(height != PL111_MAX_CURSOR_HEIGHT))
	return -EINVAL;

	obj = drm_gem_object_lookup(crtc->dev, file_priv, handle);
	if (!obj) {
	DRM_ERROR("Cannot find cursor object for handle = %d\n",
	handle);
	return -ENOENT;
	}

	/*
	* We expect a PL111_MAX_CURSOR_WIDTH x PL111_MAX_CURSOR_HEIGHT
	* ARGB888 buffer object in the input.
	*
	*/
	if (obj->size < (PL111_MAX_CURSOR_WIDTH * PL111_MAX_CURSOR_HEIGHT * 4)) {
	DRM_ERROR("Cannot set cursor with an obj size = %d\n",
	obj->size);
	drm_gem_object_unreference_unlocked(obj);
	return -EINVAL;
	}

	bo = PL111_BO_FROM_GEM(obj);
	if (!(bo->type & PL111_BOT_DMA)) {
	DRM_ERROR("Tried to set cursor with non DMA backed obj = %p\n",
	obj);
	drm_gem_object_unreference_unlocked(obj);
	return -EINVAL;
	}

	pl111_set_cursor_image(bo->backing_data.dma.fb_cpu_addr);

	/*
	* Since we copy the contents of the buffer to the HW cursor internal
	* memory this GEM object is not needed anymore.
	*/
	drm_gem_object_unreference_unlocked(obj);

	pl111_cursor_enable();

	return 0;
	}

	int pl111_crtc_cursor_move(struct drm_crtc *crtc,
	int x, int y)
	{
	int x_clip = 0;
	int y_clip = 0;

	DRM_DEBUG("x %d y %d\n", x, y);

	/*
	* The cursor image is clipped automatically at the screen limits when
	* it extends beyond the screen image to the right or bottom but
	* we must clip it using pl111 HW features for negative values.
	*/
	if (x < 0) {
	x_clip = -x;
	x = 0;
	}
	if (y < 0) {
	y_clip = -y;
	y = 0;
	}

	pl111_set_cursor_clipping(x_clip, y_clip);
	pl111_set_cursor_position(x, y);

	return 0;
	}