[PATCH 4/5] fbdev: Add support for SuperVidel's SuperBlitter

[Michael Schmitz <schmitzmic@gmail.com>]

From: Miro Kropacek <miro.kropacek@gmail.com>

The SuperVidel graphics FPGA includes a hardware blitter (bit block
transfer engine) operating within the SuperVidel DDR2 video RAM.

Two versions of this blitter exist. Later versions (>= 9) of the
SuperVidel firmware support an asynchronous command FIFO, older
versions must be polled for command completion.

Add hardware-accelerated copyarea, fillrect and imageblit fb
operations (falling back to the non-accelerated versions for
anything that exceeds blitter capabilities).

Signed-off-by: Miro Kropacek <miro.kropacek@gmail.com>
Reviewed-by: Michael Schmitz <schmitzmic@gmail.com>
Cc: <linux-fbdev@vger.kernel.org>
Link: https://lists.debian.org/debian-68k/2026/08/msg00000.html
---
 drivers/video/fbdev/atafb.c | 197 ++++++++++++++++++++++++++++++++++++
 1 file changed, 197 insertions(+)

diff --git a/drivers/video/fbdev/atafb.c b/drivers/video/fbdev/atafb.c
index 50853d7a08e3..dc2d4154e1b6 100644
--- a/drivers/video/fbdev/atafb.c
+++ b/drivers/video/fbdev/atafb.c
@@ -2304,6 +2304,185 @@ static int ext_detect(void)
 	return 1;
 }
 
+/* ------------------- SuperVidel SuperBlitter ---------------------- */
+
+/*
+ * Hardware blitter in the SuperVidel FPGA, operating within SV DDR2 RAM.
+ * FW revision >= 9 provides a command FIFO (async operation); older
+ * revisions are programmed directly with busy-polling.
+ */
+#define SVBLIT_REGS_PHYS	0x80010000
+#define SVBLIT_SRC1		0x58	/* bits 26:0 */
+#define SVBLIT_SRC2		0x5c
+#define SVBLIT_DST		0x60
+#define SVBLIT_COUNT		0x64	/* bytes per line - 1 */
+#define SVBLIT_SRC1_OFFSET	0x68	/* line start to next line start */
+#define SVBLIT_SRC2_OFFSET	0x6c
+#define SVBLIT_DST_OFFSET	0x70
+#define SVBLIT_MASK_AND_LINES	0x74	/* bits 11:0: number of lines */
+#define SVBLIT_CONTROL		0x78	/* bit 0: busy/start, bits 4:1: mode */
+#define SVBLIT_VERSION		0x7c	/* bits 9:0: FW revision */
+#define SVBLIT_FIFO		0x80	/* wr: data; rd: bit 0 empty, bit 1 full */
+
+/*
+ * SuperBlitter bug: Instead of declared 2048 bytes, 2032 is the real maximum.
+ */
+#define SVBLIT_MAX_SPAN	2032
+
+static void __iomem *svblit_regs;
+static int svblit_fw;
+
+static inline u32 svblit_rd(unsigned int reg)
+{
+	return __raw_readl(svblit_regs + reg);
+}
+
+static inline void svblit_wr(unsigned int reg, u32 val)
+{
+	__raw_writel(val, svblit_regs + reg);
+}
+
+/* wait until all queued blits have finished */
+static void svblit_wait(void)
+{
+	if (svblit_fw >= 9)
+		/* FIFO empty flag = fewer than 9 longwords queued */
+		while (!(svblit_rd(SVBLIT_FIFO) & 1))
+			cpu_relax();
+	while (svblit_rd(SVBLIT_CONTROL) & 1)
+		cpu_relax();
+}
+
+/*
+ * FW >= 9 queues commands through the 512-longword FIFO: a command is
+ * 9 longwords (registers 0x58..0x78 in order), executed whenever >= 9
+ * words are queued and the blitter is idle. The full flag rises at
+ * >= 500 queued words, so below it there is always room for a whole
+ * command — one flag check per command prevents overflow (dropped
+ * words would desync the 9-word framing until an SV reinit, which is
+ * exactly what overflowing did before this guard existed). Older FW
+ * is programmed directly with busy-polling.
+ *
+ * The line byte count field is 11 bits but see SVBLIT_MAX_SPAN.
+ */
+static void svblit_copy(u32 src, u32 dst, u32 nbytes, u32 src_offset,
+			u32 dst_offset, u32 lines)
+{
+	while (nbytes) {
+		u32 chunk = min(nbytes, SVBLIT_MAX_SPAN);
+
+		if (svblit_fw >= 9) {
+			while (svblit_rd(SVBLIT_FIFO) & 2)
+				cpu_relax();
+			svblit_wr(SVBLIT_FIFO, src);
+			svblit_wr(SVBLIT_FIFO, 0);
+			svblit_wr(SVBLIT_FIFO, dst);
+			svblit_wr(SVBLIT_FIFO, chunk - 1);
+			svblit_wr(SVBLIT_FIFO, src_offset);
+			svblit_wr(SVBLIT_FIFO, 0);
+			svblit_wr(SVBLIT_FIFO, dst_offset);
+			svblit_wr(SVBLIT_FIFO, lines);
+			svblit_wr(SVBLIT_FIFO, 0x01);
+		} else {
+			while (svblit_rd(SVBLIT_CONTROL) & 1)
+				cpu_relax();
+			svblit_wr(SVBLIT_SRC1, src);
+			svblit_wr(SVBLIT_SRC2, 0);
+			svblit_wr(SVBLIT_DST, dst);
+			svblit_wr(SVBLIT_COUNT, chunk - 1);
+			svblit_wr(SVBLIT_SRC1_OFFSET, src_offset);
+			svblit_wr(SVBLIT_SRC2_OFFSET, 0);
+			svblit_wr(SVBLIT_DST_OFFSET, dst_offset);
+			svblit_wr(SVBLIT_MASK_AND_LINES, lines);
+			svblit_wr(SVBLIT_CONTROL, 0x01);
+		}
+
+		src += chunk;
+		dst += chunk;
+		nbytes -= chunk;
+	}
+}
+
+static int svblit_sync(struct fb_info *info)
+{
+	svblit_wait();
+	return 0;
+}
+
+static void svblit_copyarea(struct fb_info *info,
+			    const struct fb_copyarea *area)
+{
+	u32 bytespp = info->var.bits_per_pixel / 8;
+	u32 pitch = info->fix.line_length;
+
+	/*
+	 * The blitter walks lines in ascending order, so overlapping
+	 * moves down/right would read already overwritten data. Those
+	 * are rare for fbcon (scrolling backwards); leave them and
+	 * oversized areas to the CPU.
+	 */
+	if (area->height > 4095 ||
+	    area->dy > area->sy ||
+	    (area->dy == area->sy && area->dx > area->sx)) {
+		svblit_wait();
+		cfb_copyarea(info, area);
+		return;
+	}
+
+	svblit_copy(external_addr + area->sy * pitch + area->sx * bytespp,
+		    external_addr + area->dy * pitch + area->dx * bytespp,
+		    area->width * bytespp, pitch, pitch, area->height);
+	/* async: every CPU access to the fb goes through svblit_wait() */
+}
+
+static void svblit_fillrect(struct fb_info *info,
+			    const struct fb_fillrect *rect)
+{
+	u32 bytespp = info->var.bits_per_pixel / 8;
+	u32 pitch = info->fix.line_length;
+	u8 *line;
+	u32 pix;
+
+	svblit_wait();		/* the CPU is about to touch the fb */
+
+	if (rect->rop != ROP_COPY || rect->height <= 1 ||
+	    rect->height > 4096) {
+		cfb_fillrect(info, rect);
+		return;
+	}
+
+	pix = (info->fix.visual == FB_VISUAL_TRUECOLOR) ?
+		((u32 *)info->pseudo_palette)[rect->color] : rect->color;
+
+	/* draw the first line with the CPU ... */
+	line = (u8 *)info->screen_base + rect->dy * pitch +
+	       rect->dx * bytespp;
+	switch (bytespp) {
+	case 1:
+		memset(line, pix, rect->width);
+		break;
+	case 2:
+		memset16((u16 *)line, pix, rect->width);
+		break;
+	default:
+		memset32((u32 *)line, pix, rect->width);
+		break;
+	}
+
+	/* ... and let the blitter replicate it into the other lines */
+	svblit_copy(external_addr + rect->dy * pitch + rect->dx * bytespp,
+		    external_addr + (rect->dy + 1) * pitch +
+		    rect->dx * bytespp,
+		    rect->width * bytespp, 0, pitch, rect->height - 1);
+}
+
+static void svblit_imageblit(struct fb_info *info,
+			     const struct fb_image *image)
+{
+	svblit_wait();		/* CPU rendering must not race queued blits */
+	cfb_imageblit(info, image);
+}
+
 #endif /* ATAFB_EXT */
 
 /* ------ This is the same for most hardware types -------- */
@@ -3168,6 +3347,24 @@ static int __init atafb_probe(struct platform_device *pdev)
 		phys_screen_base = external_addr;
 		screen_len = external_len & PAGE_MASK;
 		memset (screen_base, 0, external_len);
+
+		/* framebuffer in SV RAM: enable the SuperBlitter */
+		if (external_addr >= 0xa0000000) {
+			svblit_regs = ioremap(SVBLIT_REGS_PHYS, 0x100);
+			if (svblit_regs) {
+				svblit_fw = svblit_rd(SVBLIT_VERSION) & 0x1ff;
+				atafb_ops.fb_fillrect = svblit_fillrect;
+				atafb_ops.fb_copyarea = svblit_copyarea;
+				atafb_ops.fb_imageblit = svblit_imageblit;
+				atafb_ops.fb_sync = svblit_sync;
+				fb_info.flags |= FBINFO_HWACCEL_COPYAREA |
+						 FBINFO_HWACCEL_FILLRECT;
+				dev_info(&pdev->dev,
+					 "SuperBlitter enabled, FW revision %d (%s)\n",
+					 svblit_fw, svblit_fw >= 9 ?
+					 "async FIFO" : "sync");
+			}
+		}
 	}
 #endif /* ATAFB_EXT */
 
-- 
2.17.1