text: /*
   * Copyright (C) 2016 Noralf Trønnes
   *
   * 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.
   */
  
  #include <linux/backlight.h>
  #include <linux/dma-buf.h>
  #include <linux/pm.h>
  #include <linux/spi/spi.h>
  #include <linux/swab.h>
  
  #include <drm/tinydrm/tinydrm.h>
  #include <drm/tinydrm/tinydrm-helpers.h>
  
  static unsigned int spi_max;
  module_param(spi_max, uint, 0400);
  MODULE_PARM_DESC(spi_max, "Set a lower SPI max transfer size");
  
  /**
   * tinydrm_merge_clips - Merge clip rectangles
   * @dst: Destination clip rectangle
   * @src: Source clip rectangle(s)
   * @num_clips: Number of @src clip rectangles
   * @flags: Dirty fb ioctl flags
   * @max_width: Maximum width of @dst
   * @max_height: Maximum height of @dst
   *
   * This function merges @src clip rectangle(s) into @dst. If @src is NULL,
   * @max_width and @min_width is used to set a full @dst clip rectangle.
   *
   * Returns:
   * true if it's a full clip, false otherwise
   */
  bool tinydrm_merge_clips(struct drm_clip_rect *dst,
  			 struct drm_clip_rect *src, unsigned int num_clips,
  			 unsigned int flags, u32 max_width, u32 max_height)
  {
  	unsigned int i;
  
  	if (!src || !num_clips) {
  		dst->x1 = 0;
  		dst->x2 = max_width;
  		dst->y1 = 0;
  		dst->y2 = max_height;
  		return true;
  	}
  
  	dst->x1 = ~0;
  	dst->y1 = ~0;
  	dst->x2 = 0;
  	dst->y2 = 0;
  
  	for (i = 0; i < num_clips; i++) {
  		if (flags & DRM_MODE_FB_DIRTY_ANNOTATE_COPY)
  			i++;
  		dst->x1 = min(dst->x1, src[i].x1);
  		dst->x2 = max(dst->x2, src[i].x2);
  		dst->y1 = min(dst->y1, src[i].y1);
  		dst->y2 = max(dst->y2, src[i].y2);
  	}
  
  	if (dst->x2 > max_width || dst->y2 > max_height ||
  	    dst->x1 >= dst->x2 || dst->y1 >= dst->y2) {
  		DRM_DEBUG_KMS("Illegal clip: x1=%u, x2=%u, y1=%u, y2=%u\n",
  			      dst->x1, dst->x2, dst->y1, dst->y2);
  		dst->x1 = 0;
  		dst->y1 = 0;
  		dst->x2 = max_width;
  		dst->y2 = max_height;
  	}
  
  	return (dst->x2 - dst->x1) == max_width &&
  	       (dst->y2 - dst->y1) == max_height;
  }
  EXPORT_SYMBOL(tinydrm_merge_clips);
  
  /**
   * tinydrm_memcpy - Copy clip buffer
   * @dst: Destination buffer
   * @vaddr: Source buffer
   * @fb: DRM framebuffer
   * @clip: Clip rectangle area to copy
   */
  void tinydrm_memcpy(void *dst, void *vaddr, struct drm_framebuffer *fb,
  		    struct drm_clip_rect *clip)
  {
  	unsigned int cpp = drm_format_plane_cpp(fb->format->format, 0);
  	unsigned int pitch = fb->pitches[0];
  	void *src = vaddr + (clip->y1 * pitch) + (clip->x1 * cpp);
  	size_t len = (clip->x2 - clip->x1) * cpp;
  	unsigned int y;
  
  	for (y = clip->y1; y < clip->y2; y++) {
  		memcpy(dst, src, len);
  		src += pitch;
  		dst += len;
  	}
  }
  EXPORT_SYMBOL(tinydrm_memcpy);
  
  /**
   * tinydrm_swab16 - Swap bytes into clip buffer
   * @dst: RGB565 destination buffer
   * @vaddr: RGB565 source buffer
   * @fb: DRM framebuffer
   * @clip: Clip rectangle area to copy
   */
  void tinydrm_swab16(u16 *dst, void *vaddr, struct drm_framebuffer *fb,
  		    struct drm_clip_rect *clip)
  {
  	size_t len = (clip->x2 - clip->x1) * sizeof(u16);
  	unsigned int x, y;
  	u16 *src, *buf;
  
  	/*
  	 * The cma memory is write-combined so reads are uncached.
  	 * Speed up by fetching one line at a time.
  	 */
  	buf = kmalloc(len, GFP_KERNEL);
  	if (!buf)
  		return;
  
  	for (y = clip->y1; y < clip->y2; y++) {
  		src = vaddr + (y * fb->pitches[0]);
  		src += clip->x1;
  		memcpy(buf, src, len);
  		src = buf;
  		for (x = clip->x1; x < clip->x2; x++)
  			*dst++ = swab16(*src++);
  	}
  
  	kfree(buf);
  }
  EXPORT_SYMBOL(tinydrm_swab16);
  
  /**
   * tinydrm_xrgb8888_to_rgb565 - Convert XRGB8888 to RGB565 clip buffer
   * @dst: RGB565 destination buffer
   * @vaddr: XRGB8888 source buffer
   * @fb: DRM framebuffer
   * @clip: Clip rectangle area to copy
   * @swap: Swap bytes
   *
   * Drivers can use this function for RGB565 devices that don't natively
   * support XRGB8888.
   */
  void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
  				struct drm_framebuffer *fb,
  				struct drm_clip_rect *clip, bool swap)
  {
  	size_t len = (clip->x2 - clip->x1) * sizeof(u32);
  	unsigned int x, y;
  	u32 *src, *buf;
  	u16 val16;
  
  	buf = kmalloc(len, GFP_KERNEL);
  	if (!buf)
  		return;
  
  	for (y = clip->y1; y < clip->y2; y++) {
  		src = vaddr + (y * fb->pitches[0]);
  		src += clip->x1;
  		memcpy(buf, src, len);
  		src = buf;
  		for (x = clip->x1; x < clip->x2; x++) {
  			val16 = ((*src & 0x00F80000) >> 8) |
  				((*src & 0x0000FC00) >> 5) |
  				((*src & 0x000000F8) >> 3);
  			src++;
  			if (swap)
  				*dst++ = swab16(val16);
  			else
  				*dst++ = val16;
  		}
  	}
  
  	kfree(buf);
  }
  EXPORT_SYMBOL(tinydrm_xrgb8888_to_rgb565);
  
  /**
   * tinydrm_xrgb8888_to_gray8 - Convert XRGB8888 to grayscale
   * @dst: 8-bit grayscale destination buffer
   * @vaddr: XRGB8888 source buffer
   * @fb: DRM framebuffer
   * @clip: Clip rectangle area to copy
   *
   * Drm doesn't have native monochrome or grayscale support.
   * Such drivers can announce the commonly supported XR24 format to userspace
   * and use this function to convert to the native format.
   *
   * Monochrome drivers will use the most significant bit,
   * where 1 means foreground color and 0 background color.
   *
   * ITU BT.601 is used for the RGB -> luma (brightness) conversion.
   */
  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
  			       struct drm_clip_rect *clip)
  {
  	unsigned int len = (clip->x2 - clip->x1) * sizeof(u32);
  	unsigned int x, y;
  	void *buf;
  	u32 *src;
  
  	if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
  		return;
  	/*
  	 * The cma memory is write-combined so reads are uncached.
  	 * Speed up by fetching one line at a time.
  	 */
  	buf = kmalloc(len, GFP_KERNEL);
  	if (!buf)
  		return;
  
  	for (y = clip->y1; y < clip->y2; y++) {
  		src = vaddr + (y * fb->pitches[0]);
  		src += clip->x1;
  		memcpy(buf, src, len);
  		src = buf;
  		for (x = clip->x1; x < clip->x2; x++) {
  			u8 r = (*src & 0x00ff0000) >> 16;
  			u8 g = (*src & 0x0000ff00) >> 8;
  			u8 b =  *src & 0x000000ff;
  
  			/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
  			*dst++ = (3 * r + 6 * g + b) / 10;
  			src++;
  		}
  	}
  
  	kfree(buf);
  }
  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
  
  #if IS_ENABLED(CONFIG_SPI)
  
  /**
   * tinydrm_spi_max_transfer_size - Determine max SPI transfer size
   * @spi: SPI device
   * @max_len: Maximum buffer size needed (optional)
   *
   * This function returns the maximum size to use for SPI transfers. It checks
   * the SPI master, the optional @max_len and the module parameter spi_max and
   * returns the smallest.
   *
   * Returns:
   * Maximum size for SPI transfers
   */
  size_t tinydrm_spi_max_transfer_size(struct spi_device *spi, size_t max_len)
  {
  	size_t ret;
  
  	ret = min(spi_max_transfer_size(spi), spi->master->max_dma_len);
  	if (max_len)
  		ret = min(ret, max_len);
  	if (spi_max)
  		ret = min_t(size_t, ret, spi_max);
  	ret &= ~0x3;
  	if (ret < 4)
  		ret = 4;
  
  	return ret;
  }
  EXPORT_SYMBOL(tinydrm_spi_max_transfer_size);
  
  /**
   * tinydrm_spi_bpw_supported - Check if bits per word is supported
   * @spi: SPI device
   * @bpw: Bits per word
   *
   * This function checks to see if the SPI master driver supports @bpw.
   *
   * Returns:
   * True if @bpw is supported, false otherwise.
   */
  bool tinydrm_spi_bpw_supported(struct spi_device *spi, u8 bpw)
  {
  	u32 bpw_mask = spi->master->bits_per_word_mask;
  
  	if (bpw == 8)
  		return true;
  
  	if (!bpw_mask) {
  		dev_warn_once(&spi->dev,
  			      "bits_per_word_mask not set, assume 8-bit only\n");
  		return false;
  	}
  
  	if (bpw_mask & SPI_BPW_MASK(bpw))
  		return true;
  
  	return false;
  }
  EXPORT_SYMBOL(tinydrm_spi_bpw_supported);
  
  static void
  tinydrm_dbg_spi_print(struct spi_device *spi, struct spi_transfer *tr,
  		      const void *buf, int idx, bool tx)
  {
  	u32 speed_hz = tr->speed_hz ? tr->speed_hz : spi->max_speed_hz;
  	char linebuf[3 * 32];
  
  	hex_dump_to_buffer(buf, tr->len, 16,
  			   DIV_ROUND_UP(tr->bits_per_word, 8),
  			   linebuf, sizeof(linebuf), false);
  
  	printk(KERN_DEBUG
  	       "    tr(%i): speed=%u%s, bpw=%i, len=%u, %s_buf=[%s%s]\n", idx,
  	       speed_hz > 1000000 ? speed_hz / 1000000 : speed_hz / 1000,
  	       speed_hz > 1000000 ? "MHz" : "kHz", tr->bits_per_word, tr->len,
  	       tx ? "tx" : "rx", linebuf, tr->len > 16 ? " ..." : "");
  }
  
  /* called through tinydrm_dbg_spi_message() */
  void _tinydrm_dbg_spi_message(struct spi_device *spi, struct spi_message *m)
  {
  	struct spi_transfer *tmp;
  	int i = 0;
  
  	list_for_each_entry(tmp, &m->transfers, transfer_list) {
  
  		if (tmp->tx_buf)
  			tinydrm_dbg_spi_print(spi, tmp, tmp->tx_buf, i, true);
  		if (tmp->rx_buf)
  			tinydrm_dbg_spi_print(spi, tmp, tmp->rx_buf, i, false);
  		i++;
  	}
  }
  EXPORT_SYMBOL(_tinydrm_dbg_spi_message);
  
  /**
   * tinydrm_spi_transfer - SPI transfer helper
   * @spi: SPI device
   * @speed_hz: Override speed (optional)
   * @header: Optional header transfer
   * @bpw: Bits per word
   * @buf: Buffer to transfer
   * @len: Buffer length
   *
   * This SPI transfer helper breaks up the transfer of @buf into chunks which
   * the SPI master driver can handle. If the machine is Little Endian and the
   * SPI master driver doesn't support 16 bits per word, it swaps the bytes and
   * does a 8-bit transfer.
   * If @header is set, it is prepended to each SPI message.
   *
   * Returns:
   * Zero on success, negative error code on failure.
   */
  int tinydrm_spi_transfer(struct spi_device *spi, u32 speed_hz,
  			 struct spi_transfer *header, u8 bpw, const void *buf,
  			 size_t len)
  {
  	struct spi_transfer tr = {
  		.bits_per_word = bpw,
  		.speed_hz = speed_hz,
  	};
  	struct spi_message m;
  	u16 *swap_buf = NULL;
  	size_t max_chunk;
  	size_t chunk;
  	int ret = 0;
  
  	if (WARN_ON_ONCE(bpw != 8 && bpw != 16))
  		return -EINVAL;
  
  	max_chunk = tinydrm_spi_max_transfer_size(spi, 0);
  
  	if (drm_debug & DRM_UT_DRIVER)
  		pr_debug("[drm:%s] bpw=%u, max_chunk=%zu, transfers:\n",
  			 __func__, bpw, max_chunk);
  
  	if (bpw == 16 && !tinydrm_spi_bpw_supported(spi, 16)) {
  		tr.bits_per_word = 8;
  		if (tinydrm_machine_little_endian()) {
  			swap_buf = kmalloc(min(len, max_chunk), GFP_KERNEL);
  			if (!swap_buf)
  				return -ENOMEM;
  		}
  	}
  
  	spi_message_init(&m);
  	if (header)
  		spi_message_add_tail(header, &m);
  	spi_message_add_tail(&tr, &m);
  
  	while (len) {
  		chunk = min(len, max_chunk);
  
  		tr.tx_buf = buf;
  		tr.len = chunk;
  
  		if (swap_buf) {
  			const u16 *buf16 = buf;
  			unsigned int i;
  
  			for (i = 0; i < chunk / 2; i++)
  				swap_buf[i] = swab16(buf16[i]);
  
  			tr.tx_buf = swap_buf;
  		}
  
  		buf += chunk;
  		len -= chunk;
  
  		tinydrm_dbg_spi_message(spi, &m);
  		ret = spi_sync(spi, &m);
  		if (ret)
  			return ret;
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL(tinydrm_spi_transfer);
  
  #endif /* CONFIG_SPI */
  