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From ba65074e39e6aee492bd3c077f640b29a0a89c05 Mon Sep 17 00:00:00 2001
From: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Date: Mon, 17 Jun 2013 16:00:25 +0300
Subject: [PATCH 070/174] bcm2708_fb: DMA acceleration for fb_copyarea
Based on http://www.raspberrypi.org/phpBB3/viewtopic.php?p=62425#p62425
Also used Simon's dmaer_master module as a reference for tweaking DMA
settings for better performance.
For now busylooping only. IRQ support might be added later.
With non-overclocked Raspberry Pi, the performance is ~360 MB/s
for simple copy or ~260 MB/s for two-pass copy (used when dragging
windows to the right).
In the case of using DMA channel 0, the performance improves
to ~440 MB/s.
For comparison, VFP optimized CPU copy can only do ~114 MB/s in
the same conditions (hindered by reading uncached source buffer).
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
---
drivers/video/bcm2708_fb.c | 162 ++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 159 insertions(+), 3 deletions(-)
--- a/drivers/video/bcm2708_fb.c
+++ b/drivers/video/bcm2708_fb.c
@@ -28,6 +28,7 @@
#include <linux/printk.h>
#include <linux/console.h>
+#include <mach/dma.h>
#include <mach/platform.h>
#include <mach/vcio.h>
@@ -63,6 +64,11 @@ struct bcm2708_fb {
struct fbinfo_s *info;
dma_addr_t dma;
u32 cmap[16];
+ int dma_chan;
+ int dma_irq;
+ void __iomem *dma_chan_base;
+ void *cb_base; /* DMA control blocks */
+ dma_addr_t cb_handle;
};
#define to_bcm2708(info) container_of(info, struct bcm2708_fb, fb)
@@ -312,11 +318,133 @@ static void bcm2708_fb_fillrect(struct f
cfb_fillrect(info, rect);
}
+/* A helper function for configuring dma control block */
+static void set_dma_cb(struct bcm2708_dma_cb *cb,
+ int burst_size,
+ dma_addr_t dst,
+ int dst_stride,
+ dma_addr_t src,
+ int src_stride,
+ int w,
+ int h)
+{
+ cb->info = BCM2708_DMA_BURST(burst_size) | BCM2708_DMA_S_WIDTH |
+ BCM2708_DMA_S_INC | BCM2708_DMA_D_WIDTH |
+ BCM2708_DMA_D_INC | BCM2708_DMA_TDMODE;
+ cb->dst = dst;
+ cb->src = src;
+ /*
+ * This is not really obvious from the DMA documentation,
+ * but the top 16 bits must be programmmed to "height -1"
+ * and not "height" in 2D mode.
+ */
+ cb->length = ((h - 1) << 16) | w;
+ cb->stride = ((dst_stride - w) << 16) | (u16)(src_stride - w);
+ cb->pad[0] = 0;
+ cb->pad[1] = 0;
+}
+
static void bcm2708_fb_copyarea(struct fb_info *info,
const struct fb_copyarea *region)
{
- /*print_debug("bcm2708_fb_copyarea\n"); */
- cfb_copyarea(info, region);
+ struct bcm2708_fb *fb = to_bcm2708(info);
+ struct bcm2708_dma_cb *cb = fb->cb_base;
+ int bytes_per_pixel = (info->var.bits_per_pixel + 7) >> 3;
+ /* Channel 0 supports larger bursts and is a bit faster */
+ int burst_size = (fb->dma_chan == 0) ? 8 : 2;
+
+ /* Fallback to cfb_copyarea() if we don't like something */
+ if (bytes_per_pixel > 4 ||
+ info->var.xres > 1920 || info->var.yres > 1200 ||
+ region->width <= 0 || region->width > info->var.xres ||
+ region->height <= 0 || region->height > info->var.yres ||
+ region->sx < 0 || region->sx >= info->var.xres ||
+ region->sy < 0 || region->sy >= info->var.yres ||
+ region->dx < 0 || region->dx >= info->var.xres ||
+ region->dy < 0 || region->dy >= info->var.yres ||
+ region->sx + region->width > info->var.xres ||
+ region->dx + region->width > info->var.xres ||
+ region->sy + region->height > info->var.yres ||
+ region->dy + region->height > info->var.yres) {
+ cfb_copyarea(info, region);
+ return;
+ }
+
+ if (region->dy == region->sy && region->dx > region->sx) {
+ /*
+ * A difficult case of overlapped copy. Because DMA can't
+ * copy individual scanlines in backwards direction, we need
+ * two-pass processing. We do it by programming a chain of dma
+ * control blocks in the first 16K part of the buffer and use
+ * the remaining 48K as the intermediate temporary scratch
+ * buffer. The buffer size is sufficient to handle up to
+ * 1920x1200 resolution at 32bpp pixel depth.
+ */
+ int y;
+ dma_addr_t control_block_pa = fb->cb_handle;
+ dma_addr_t scratchbuf = fb->cb_handle + 16 * 1024;
+ int scanline_size = bytes_per_pixel * region->width;
+ int scanlines_per_cb = (64 * 1024 - 16 * 1024) / scanline_size;
+
+ for (y = 0; y < region->height; y += scanlines_per_cb) {
+ dma_addr_t src =
+ fb->fb.fix.smem_start +
+ bytes_per_pixel * region->sx +
+ (region->sy + y) * fb->fb.fix.line_length;
+ dma_addr_t dst =
+ fb->fb.fix.smem_start +
+ bytes_per_pixel * region->dx +
+ (region->dy + y) * fb->fb.fix.line_length;
+
+ if (region->height - y < scanlines_per_cb)
+ scanlines_per_cb = region->height - y;
+
+ set_dma_cb(cb, burst_size, scratchbuf, scanline_size,
+ src, fb->fb.fix.line_length,
+ scanline_size, scanlines_per_cb);
+ control_block_pa += sizeof(struct bcm2708_dma_cb);
+ cb->next = control_block_pa;
+ cb++;
+
+ set_dma_cb(cb, burst_size, dst, fb->fb.fix.line_length,
+ scratchbuf, scanline_size,
+ scanline_size, scanlines_per_cb);
+ control_block_pa += sizeof(struct bcm2708_dma_cb);
+ cb->next = control_block_pa;
+ cb++;
+ }
+ /* move the pointer back to the last dma control block */
+ cb--;
+ } else {
+ /* A single dma control block is enough. */
+ int sy, dy, stride;
+ if (region->dy <= region->sy) {
+ /* processing from top to bottom */
+ dy = region->dy;
+ sy = region->sy;
+ stride = fb->fb.fix.line_length;
+ } else {
+ /* processing from bottom to top */
+ dy = region->dy + region->height - 1;
+ sy = region->sy + region->height - 1;
+ stride = -fb->fb.fix.line_length;
+ }
+ set_dma_cb(cb, burst_size,
+ fb->fb.fix.smem_start + dy * fb->fb.fix.line_length +
+ bytes_per_pixel * region->dx,
+ stride,
+ fb->fb.fix.smem_start + sy * fb->fb.fix.line_length +
+ bytes_per_pixel * region->sx,
+ stride,
+ region->width * bytes_per_pixel,
+ region->height);
+ }
+
+ /* end of dma control blocks chain */
+ cb->next = 0;
+
+ bcm_dma_start(fb->dma_chan_base, fb->cb_handle);
+ bcm_dma_wait_idle(fb->dma_chan_base);
}
static void bcm2708_fb_imageblit(struct fb_info *info,
@@ -359,7 +487,7 @@ static int bcm2708_fb_register(struct bc
fb->dma = dma;
}
fb->fb.fbops = &bcm2708_fb_ops;
- fb->fb.flags = FBINFO_FLAG_DEFAULT;
+ fb->fb.flags = FBINFO_FLAG_DEFAULT | FBINFO_HWACCEL_COPYAREA;
fb->fb.pseudo_palette = fb->cmap;
strncpy(fb->fb.fix.id, bcm2708_name, sizeof(fb->fb.fix.id));
@@ -424,6 +552,28 @@ static int bcm2708_fb_probe(struct platf
}
memset(fb, 0, sizeof(struct bcm2708_fb));
+ fb->cb_base = dma_alloc_writecombine(&dev->dev, SZ_64K,
+ &fb->cb_handle, GFP_KERNEL);
+ if (!fb->cb_base) {
+ dev_err(&dev->dev, "cannot allocate DMA CBs\n");
+ ret = -ENOMEM;
+ goto free_fb;
+ }
+
+ pr_info("BCM2708FB: allocated DMA memory %08x\n",
+ fb->cb_handle);
+
+ ret = bcm_dma_chan_alloc(BCM_DMA_FEATURE_BULK,
+ &fb->dma_chan_base, &fb->dma_irq);
+ if (ret < 0) {
+ dev_err(&dev->dev, "couldn't allocate a DMA channel\n");
+ goto free_cb;
+ }
+ fb->dma_chan = ret;
+
+ pr_info("BCM2708FB: allocated DMA channel %d @ %p\n",
+ fb->dma_chan, fb->dma_chan_base);
+
fb->dev = dev;
ret = bcm2708_fb_register(fb);
@@ -432,6 +582,9 @@ static int bcm2708_fb_probe(struct platf
goto out;
}
+free_cb:
+ dma_free_writecombine(&dev->dev, SZ_64K, fb->cb_base, fb->cb_handle);
+free_fb:
kfree(fb);
free_region:
dev_err(&dev->dev, "probe failed, err %d\n", ret);
@@ -449,6 +602,9 @@ static int bcm2708_fb_remove(struct plat
iounmap(fb->fb.screen_base);
unregister_framebuffer(&fb->fb);
+ dma_free_writecombine(&dev->dev, SZ_64K, fb->cb_base, fb->cb_handle);
+ bcm_dma_chan_free(fb->dma_chan);
+
dma_free_coherent(NULL, PAGE_ALIGN(sizeof(*fb->info)), (void *)fb->info,
fb->dma);
kfree(fb);
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