207 lines
6.0 KiB
Diff
207 lines
6.0 KiB
Diff
From ab41011a32fdc35352ee6b308f29b6954056d787 Mon Sep 17 00:00:00 2001
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From: Luke Diamand <luked@broadcom.com>
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Date: Wed, 1 Jan 2014 00:45:29 +0000
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Subject: [PATCH 149/174] bcm2708_fb: use IRQ for DMA copies
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The copyarea ioctl() uses DMA to speed things along. This
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was busy-waiting for completion. This change supports using
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an interrupt instead for larger transfers. For small
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transfers, busy-waiting is still likely to be faster.
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Signed-off-by: Luke Diamand <luke@diamand.org>
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---
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arch/arm/mach-bcm2708/dma.c | 8 ++++
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arch/arm/mach-bcm2708/include/mach/dma.h | 2 +
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drivers/video/bcm2708_fb.c | 64 ++++++++++++++++++++++++++++++--
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3 files changed, 70 insertions(+), 4 deletions(-)
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--- a/arch/arm/mach-bcm2708/dma.c
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+++ b/arch/arm/mach-bcm2708/dma.c
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@@ -83,6 +83,14 @@ extern void bcm_dma_wait_idle(void __iom
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EXPORT_SYMBOL_GPL(bcm_dma_start);
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+extern bool bcm_dma_is_busy(void __iomem *dma_chan_base)
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+{
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+ dsb();
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+
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+ return readl(dma_chan_base + BCM2708_DMA_CS) & BCM2708_DMA_ACTIVE;
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+}
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+EXPORT_SYMBOL_GPL(bcm_dma_is_busy);
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+
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/* Complete an ongoing DMA (assuming its results are to be ignored)
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Does nothing if there is no DMA in progress.
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This routine waits for the current AXI transfer to complete before
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--- a/arch/arm/mach-bcm2708/include/mach/dma.h
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+++ b/arch/arm/mach-bcm2708/include/mach/dma.h
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@@ -64,11 +64,13 @@ struct bcm2708_dma_cb {
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unsigned long next;
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unsigned long pad[2];
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};
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+struct scatterlist;
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extern int bcm_sg_suitable_for_dma(struct scatterlist *sg_ptr, int sg_len);
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extern void bcm_dma_start(void __iomem *dma_chan_base,
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dma_addr_t control_block);
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extern void bcm_dma_wait_idle(void __iomem *dma_chan_base);
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+extern bool bcm_dma_is_busy(void __iomem *dma_chan_base);
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extern int /*rc*/ bcm_dma_abort(void __iomem *dma_chan_base);
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/* When listing features we can ask for when allocating DMA channels give
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--- a/drivers/video/bcm2708_fb.c
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+++ b/drivers/video/bcm2708_fb.c
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@@ -21,6 +21,7 @@
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#include <linux/mm.h>
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#include <linux/fb.h>
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#include <linux/init.h>
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+#include <linux/interrupt.h>
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#include <linux/ioport.h>
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#include <linux/list.h>
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#include <linux/platform_device.h>
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@@ -48,6 +49,11 @@ static const char *bcm2708_name = "BCM27
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#define DRIVER_NAME "bcm2708_fb"
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+static u32 dma_busy_wait_threshold = 1<<15;
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+module_param(dma_busy_wait_threshold, int, 0644);
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+MODULE_PARM_DESC(dma_busy_wait_threshold, "Busy-wait for DMA completion below this area");
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+
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+
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/* this data structure describes each frame buffer device we find */
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struct fbinfo_s {
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@@ -77,6 +83,7 @@ struct bcm2708_fb {
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void *cb_base; /* DMA control blocks */
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dma_addr_t cb_handle;
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struct dentry *debugfs_dir;
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+ wait_queue_head_t dma_waitq;
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struct bcm2708_fb_stats stats;
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};
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@@ -95,6 +102,10 @@ static int bcm2708_fb_debugfs_init(struc
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"dma_copies",
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offsetof(struct bcm2708_fb_stats, dma_copies)
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},
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+ {
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+ "dma_irqs",
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+ offsetof(struct bcm2708_fb_stats, dma_irqs)
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+ },
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};
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fb->debugfs_dir = debugfs_create_dir(DRIVER_NAME, NULL);
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@@ -400,6 +411,7 @@ static void bcm2708_fb_copyarea(struct f
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int bytes_per_pixel = (info->var.bits_per_pixel + 7) >> 3;
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/* Channel 0 supports larger bursts and is a bit faster */
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int burst_size = (fb->dma_chan == 0) ? 8 : 2;
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+ int pixels = region->width * region->height;
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/* Fallback to cfb_copyarea() if we don't like something */
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if (bytes_per_pixel > 4 ||
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@@ -492,8 +504,20 @@ static void bcm2708_fb_copyarea(struct f
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cb->next = 0;
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- bcm_dma_start(fb->dma_chan_base, fb->cb_handle);
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- bcm_dma_wait_idle(fb->dma_chan_base);
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+ if (pixels < dma_busy_wait_threshold) {
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+ bcm_dma_start(fb->dma_chan_base, fb->cb_handle);
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+ bcm_dma_wait_idle(fb->dma_chan_base);
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+ } else {
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+ void __iomem *dma_chan = fb->dma_chan_base;
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+ cb->info |= BCM2708_DMA_INT_EN;
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+ bcm_dma_start(fb->dma_chan_base, fb->cb_handle);
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+ while (bcm_dma_is_busy(dma_chan)) {
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+ wait_event_interruptible(
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+ fb->dma_waitq,
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+ !bcm_dma_is_busy(dma_chan));
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+ }
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+ fb->stats.dma_irqs++;
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+ }
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fb->stats.dma_copies++;
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}
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@@ -504,6 +528,24 @@ static void bcm2708_fb_imageblit(struct
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cfb_imageblit(info, image);
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}
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+static irqreturn_t bcm2708_fb_dma_irq(int irq, void *cxt)
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+{
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+ struct bcm2708_fb *fb = cxt;
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+
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+ /* FIXME: should read status register to check if this is
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+ * actually interrupting us or not, in case this interrupt
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+ * ever becomes shared amongst several DMA channels
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+ *
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+ * readl(dma_chan_base + BCM2708_DMA_CS) & BCM2708_DMA_IRQ;
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+ */
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+
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+ /* acknowledge the interrupt */
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+ writel(BCM2708_DMA_INT, fb->dma_chan_base + BCM2708_DMA_CS);
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+
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+ wake_up(&fb->dma_waitq);
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+ return IRQ_HANDLED;
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+}
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+
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static struct fb_ops bcm2708_fb_ops = {
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.owner = THIS_MODULE,
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.fb_check_var = bcm2708_fb_check_var,
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@@ -568,6 +610,7 @@ static int bcm2708_fb_register(struct bc
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fb->fb.monspecs.dclkmax = 100000000;
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bcm2708_fb_set_bitfields(&fb->fb.var);
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+ init_waitqueue_head(&fb->dma_waitq);
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/*
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* Allocate colourmap.
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@@ -593,14 +636,15 @@ static int bcm2708_fb_probe(struct platf
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struct bcm2708_fb *fb;
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int ret;
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- fb = kmalloc(sizeof(struct bcm2708_fb), GFP_KERNEL);
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+ fb = kzalloc(sizeof(struct bcm2708_fb), GFP_KERNEL);
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if (!fb) {
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dev_err(&dev->dev,
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"could not allocate new bcm2708_fb struct\n");
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ret = -ENOMEM;
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goto free_region;
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}
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- memset(fb, 0, sizeof(struct bcm2708_fb));
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+
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+ bcm2708_fb_debugfs_init(fb);
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bcm2708_fb_debugfs_init(fb);
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@@ -624,6 +668,14 @@ static int bcm2708_fb_probe(struct platf
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}
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fb->dma_chan = ret;
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+ ret = request_irq(fb->dma_irq, bcm2708_fb_dma_irq,
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+ 0, "bcm2708_fb dma", fb);
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+ if (ret) {
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+ pr_err("%s: failed to request DMA irq\n", __func__);
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+ goto free_dma_chan;
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+ }
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+
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+
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pr_info("BCM2708FB: allocated DMA channel %d @ %p\n",
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fb->dma_chan, fb->dma_chan_base);
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@@ -635,6 +687,8 @@ static int bcm2708_fb_probe(struct platf
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goto out;
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}
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+free_dma_chan:
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+ bcm_dma_chan_free(fb->dma_chan);
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free_cb:
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dma_free_writecombine(&dev->dev, SZ_64K, fb->cb_base, fb->cb_handle);
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free_fb:
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@@ -662,6 +716,8 @@ static int bcm2708_fb_remove(struct plat
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fb->dma);
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bcm2708_fb_debugfs_deinit(fb);
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+ free_irq(fb->dma_irq, fb);
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+
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kfree(fb);
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return 0;
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