drm: via driver update to CVS version

This updates the DRM via driver to the latest CVS version, which contains
support for DMA blitting.

It also contains some whitespace and other minor fixes

From: Thomas Hellstrom <unichrome@shipmail.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>

1 files changed, 805 insertions, 0 deletions

diff --git a/drivers/char/drm/via_dmablit.c b/drivers/char/drm/via_dmablit.c
new file mode 100644
index 000000000000..9d5e027dae0e
--- /dev/null
+++ b/drivers/char/drm/via_dmablit.c
@@ -0,0 +1,805 @@
+/* via_dmablit.c -- PCI DMA BitBlt support for the VIA Unichrome/Pro
+ * 
+ * Copyright (C) 2005 Thomas Hellstrom, All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sub license,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, 
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE 
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: 
+ *    Thomas Hellstrom.
+ *    Partially based on code obtained from Digeo Inc.
+ */
+
+
+/*
+ * Unmaps the DMA mappings. 
+ * FIXME: Is this a NoOp on x86? Also 
+ * FIXME: What happens if this one is called and a pending blit has previously done 
+ * the same DMA mappings? 
+ */
+
+#include "drmP.h"
+#include "via_drm.h"
+#include "via_drv.h"
+#include "via_dmablit.h"
+
+#include <linux/pagemap.h>
+
+#define VIA_PGDN(x)             (((unsigned long)(x)) & PAGE_MASK)
+#define VIA_PGOFF(x)            (((unsigned long)(x)) & ~PAGE_MASK)
+#define VIA_PFN(x)              ((unsigned long)(x) >> PAGE_SHIFT)
+
+typedef struct _drm_via_descriptor {
+        uint32_t mem_addr;
+        uint32_t dev_addr;
+        uint32_t size;
+        uint32_t next;
+} drm_via_descriptor_t;
+
+
+/*
+ * Unmap a DMA mapping.
+ */
+
+
+
+static void
+via_unmap_blit_from_device(struct pci_dev *pdev, drm_via_sg_info_t *vsg)
+{
+        int num_desc = vsg->num_desc;
+        unsigned cur_descriptor_page = num_desc / vsg->descriptors_per_page;
+        unsigned descriptor_this_page = num_desc % vsg->descriptors_per_page;
+        drm_via_descriptor_t *desc_ptr = vsg->desc_pages[cur_descriptor_page] + 
+                descriptor_this_page;
+        dma_addr_t next = vsg->chain_start;
+
+        while(num_desc--) {
+                if (descriptor_this_page-- == 0) {
+                        cur_descriptor_page--;
+                        descriptor_this_page = vsg->descriptors_per_page - 1;
+                        desc_ptr = vsg->desc_pages[cur_descriptor_page] + 
+                                descriptor_this_page;
+                }
+                dma_unmap_single(&pdev->dev, next, sizeof(*desc_ptr), DMA_TO_DEVICE);
+                dma_unmap_page(&pdev->dev, desc_ptr->mem_addr, desc_ptr->size, vsg->direction);
+                next = (dma_addr_t) desc_ptr->next;
+                desc_ptr--;
+        }
+}
+
+/*
+ * If mode = 0, count how many descriptors are needed.
+ * If mode = 1, Map the DMA pages for the device, put together and map also the descriptors.
+ * Descriptors are run in reverse order by the hardware because we are not allowed to update the
+ * 'next' field without syncing calls when the descriptor is already mapped.
+ */
+
+static void
+via_map_blit_for_device(struct pci_dev *pdev,
+                   const drm_via_dmablit_t *xfer,
+                   drm_via_sg_info_t *vsg, 
+                   int mode)
+{
+        unsigned cur_descriptor_page = 0;
+        unsigned num_descriptors_this_page = 0;
+        unsigned char *mem_addr = xfer->mem_addr;
+        unsigned char *cur_mem;
+        unsigned char *first_addr = (unsigned char *)VIA_PGDN(mem_addr);
+        uint32_t fb_addr = xfer->fb_addr;
+        uint32_t cur_fb;
+        unsigned long line_len;
+        unsigned remaining_len;
+        int num_desc = 0;
+        int cur_line;
+        dma_addr_t next = 0 | VIA_DMA_DPR_EC;
+        drm_via_descriptor_t *desc_ptr = 0;
+
+        if (mode == 1) 
+                desc_ptr = vsg->desc_pages[cur_descriptor_page];
+
+        for (cur_line = 0; cur_line < xfer->num_lines; ++cur_line) {
+
+                line_len = xfer->line_length;
+                cur_fb = fb_addr;
+                cur_mem = mem_addr;
+                
+                while (line_len > 0) {
+
+                        remaining_len = min(PAGE_SIZE-VIA_PGOFF(cur_mem), line_len);
+                        line_len -= remaining_len;
+
+                        if (mode == 1) {
+                                desc_ptr->mem_addr = 
+                                        dma_map_page(&pdev->dev, 
+                                                     vsg->pages[VIA_PFN(cur_mem) - 
+                                                                VIA_PFN(first_addr)],
+                                                     VIA_PGOFF(cur_mem), remaining_len, 
+                                                     vsg->direction);
+                                desc_ptr->dev_addr = cur_fb;
+                                
+                                desc_ptr->size = remaining_len;
+                                desc_ptr->next = (uint32_t) next;
+                                next = dma_map_single(&pdev->dev, desc_ptr, sizeof(*desc_ptr), 
+                                                      DMA_TO_DEVICE);
+                                desc_ptr++;
+                                if (++num_descriptors_this_page >= vsg->descriptors_per_page) {
+                                        num_descriptors_this_page = 0;
+                                        desc_ptr = vsg->desc_pages[++cur_descriptor_page];
+                                }
+                        }
+                        
+                        num_desc++;
+                        cur_mem += remaining_len;
+                        cur_fb += remaining_len;
+                }
+                
+                mem_addr += xfer->mem_stride;
+                fb_addr += xfer->fb_stride;
+        }
+
+        if (mode == 1) {
+                vsg->chain_start = next;
+                vsg->state = dr_via_device_mapped;
+        }
+        vsg->num_desc = num_desc;
+}
+
+/*
+ * Function that frees up all resources for a blit. It is usable even if the 
+ * blit info has only be partially built as long as the status enum is consistent
+ * with the actual status of the used resources.
+ */
+
+
+void
+via_free_sg_info(struct pci_dev *pdev, drm_via_sg_info_t *vsg) 
+{
+        struct page *page;
+        int i;
+
+        switch(vsg->state) {
+        case dr_via_device_mapped:
+                via_unmap_blit_from_device(pdev, vsg);
+        case dr_via_desc_pages_alloc:
+                for (i=0; i<vsg->num_desc_pages; ++i) {
+                        if (vsg->desc_pages[i] != NULL)
+                          free_page((unsigned long)vsg->desc_pages[i]);
+                }
+                kfree(vsg->desc_pages);
+        case dr_via_pages_locked:
+                for (i=0; i<vsg->num_pages; ++i) {
+                        if ( NULL != (page = vsg->pages[i])) {
+                                if (! PageReserved(page) && (DMA_FROM_DEVICE == vsg->direction)) 
+                                        SetPageDirty(page);
+                                page_cache_release(page);
+                        }
+                }
+        case dr_via_pages_alloc:
+                vfree(vsg->pages);
+        default:
+                vsg->state = dr_via_sg_init;
+        }
+        if (vsg->bounce_buffer) {
+                vfree(vsg->bounce_buffer);
+                vsg->bounce_buffer = NULL;
+        }
+        vsg->free_on_sequence = 0;
+}               
+
+/*
+ * Fire a blit engine.
+ */
+
+static void
+via_fire_dmablit(drm_device_t *dev, drm_via_sg_info_t *vsg, int engine)
+{
+        drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private;
+
+        VIA_WRITE(VIA_PCI_DMA_MAR0 + engine*0x10, 0);
+        VIA_WRITE(VIA_PCI_DMA_DAR0 + engine*0x10, 0);
+        VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_DD | VIA_DMA_CSR_TD | 
+                  VIA_DMA_CSR_DE);
+        VIA_WRITE(VIA_PCI_DMA_MR0  + engine*0x04, VIA_DMA_MR_CM | VIA_DMA_MR_TDIE);
+        VIA_WRITE(VIA_PCI_DMA_BCR0 + engine*0x10, 0);
+        VIA_WRITE(VIA_PCI_DMA_DPR0 + engine*0x10, vsg->chain_start);
+        VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_DE | VIA_DMA_CSR_TS);
+}
+
+/*
+ * Obtain a page pointer array and lock all pages into system memory. A segmentation violation will
+ * occur here if the calling user does not have access to the submitted address.
+ */
+
+static int
+via_lock_all_dma_pages(drm_via_sg_info_t *vsg,  drm_via_dmablit_t *xfer)
+{
+        int ret;
+        unsigned long first_pfn = VIA_PFN(xfer->mem_addr);
+        vsg->num_pages = VIA_PFN(xfer->mem_addr + (xfer->num_lines * xfer->mem_stride -1)) - 
+                first_pfn + 1;
+        
+        if (NULL == (vsg->pages = vmalloc(sizeof(struct page *) * vsg->num_pages)))
+                return DRM_ERR(ENOMEM);
+        memset(vsg->pages, 0, sizeof(struct page *) * vsg->num_pages);
+        down_read(&current->mm->mmap_sem);
+        ret = get_user_pages(current, current->mm, (unsigned long) xfer->mem_addr,
+                             vsg->num_pages, vsg->direction, 0, vsg->pages, NULL);
+
+        up_read(&current->mm->mmap_sem);
+        if (ret != vsg->num_pages) {
+                if (ret < 0) 
+                        return ret;
+                vsg->state = dr_via_pages_locked;
+                return DRM_ERR(EINVAL);
+        }
+        vsg->state = dr_via_pages_locked;
+        DRM_DEBUG("DMA pages locked\n");
+        return 0;
+}
+
+/*
+ * Allocate DMA capable memory for the blit descriptor chain, and an array that keeps track of the
+ * pages we allocate. We don't want to use kmalloc for the descriptor chain because it may be
+ * quite large for some blits, and pages don't need to be contingous.
+ */
+
+static int 
+via_alloc_desc_pages(drm_via_sg_info_t *vsg)
+{
+        int i;
+        
+        vsg->descriptors_per_page = PAGE_SIZE / sizeof( drm_via_descriptor_t);
+        vsg->num_desc_pages = (vsg->num_desc + vsg->descriptors_per_page - 1) / 
+                vsg->descriptors_per_page;
+
+        if (NULL ==  (vsg->desc_pages = kmalloc(sizeof(void *) * vsg->num_desc_pages, GFP_KERNEL))) 
+                return DRM_ERR(ENOMEM);
+        
+        memset(vsg->desc_pages, 0, sizeof(void *) * vsg->num_desc_pages);
+        vsg->state = dr_via_desc_pages_alloc;
+        for (i=0; i<vsg->num_desc_pages; ++i) {
+                if (NULL == (vsg->desc_pages[i] = 
+                             (drm_via_descriptor_t *) __get_free_page(GFP_KERNEL)))
+                        return DRM_ERR(ENOMEM);
+        }
+        DRM_DEBUG("Allocated %d pages for %d descriptors.\n", vsg->num_desc_pages,
+                  vsg->num_desc);
+        return 0;
+}
+                        
+static void
+via_abort_dmablit(drm_device_t *dev, int engine)
+{
+        drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private;
+
+        VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_TA);
+}
+
+static void
+via_dmablit_engine_off(drm_device_t *dev, int engine)
+{
+        drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private;
+
+        VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_TD | VIA_DMA_CSR_DD); 
+}
+
+
+
+/*
+ * The dmablit part of the IRQ handler. Trying to do only reasonably fast things here.
+ * The rest, like unmapping and freeing memory for done blits is done in a separate workqueue
+ * task. Basically the task of the interrupt handler is to submit a new blit to the engine, while
+ * the workqueue task takes care of processing associated with the old blit.
+ */
+                
+void
+via_dmablit_handler(drm_device_t *dev, int engine, int from_irq)
+{
+        drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private;
+        drm_via_blitq_t *blitq = dev_priv->blit_queues + engine;
+        int cur;
+        int done_transfer;
+        unsigned long irqsave=0;
+        uint32_t status = 0;
+
+        DRM_DEBUG("DMA blit handler called. engine = %d, from_irq = %d, blitq = 0x%lx\n",
+                  engine, from_irq, (unsigned long) blitq);
+
+        if (from_irq) {
+                spin_lock(&blitq->blit_lock);
+        } else {
+                spin_lock_irqsave(&blitq->blit_lock, irqsave);
+        }
+
+        done_transfer = blitq->is_active && 
+          (( status = VIA_READ(VIA_PCI_DMA_CSR0 + engine*0x04)) & VIA_DMA_CSR_TD);
+        done_transfer = done_transfer || ( blitq->aborting && !(status & VIA_DMA_CSR_DE)); 
+
+        cur = blitq->cur;
+        if (done_transfer) {
+
+                blitq->blits[cur]->aborted = blitq->aborting;
+                blitq->done_blit_handle++;
+                DRM_WAKEUP(blitq->blit_queue + cur);            
+
+                cur++;
+                if (cur >= VIA_NUM_BLIT_SLOTS) 
+                        cur = 0;
+                blitq->cur = cur;
+
+                /*
+                 * Clear transfer done flag.
+                 */
+
+                VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04,  VIA_DMA_CSR_TD);
+
+                blitq->is_active = 0;
+                blitq->aborting = 0;
+                schedule_work(&blitq->wq);      
+
+        } else if (blitq->is_active && time_after_eq(jiffies, blitq->end)) {
+
+                /*
+                 * Abort transfer after one second.
+                 */
+
+                via_abort_dmablit(dev, engine);
+                blitq->aborting = 1;
+                blitq->end = jiffies + DRM_HZ;
+        }
+                        
+        if (!blitq->is_active) {
+                if (blitq->num_outstanding) {
+                        via_fire_dmablit(dev, blitq->blits[cur], engine);
+                        blitq->is_active = 1;
+                        blitq->cur = cur;
+                        blitq->num_outstanding--;
+                        blitq->end = jiffies + DRM_HZ;
+                        if (!timer_pending(&blitq->poll_timer)) {
+                                blitq->poll_timer.expires = jiffies+1;
+                                add_timer(&blitq->poll_timer);
+                        }
+                } else {
+                        if (timer_pending(&blitq->poll_timer)) {
+                                del_timer(&blitq->poll_timer);
+                        }
+                        via_dmablit_engine_off(dev, engine);
+                }
+        }               
+
+        if (from_irq) {
+                spin_unlock(&blitq->blit_lock);
+        } else {
+                spin_unlock_irqrestore(&blitq->blit_lock, irqsave);
+        }
+} 
+
+
+
+/*
+ * Check whether this blit is still active, performing necessary locking.
+ */
+
+static int
+via_dmablit_active(drm_via_blitq_t *blitq, int engine, uint32_t handle, wait_queue_head_t **queue)
+{
+        unsigned long irqsave;
+        uint32_t slot;
+        int active;
+
+        spin_lock_irqsave(&blitq->blit_lock, irqsave);
+
+        /*
+         * Allow for handle wraparounds.
+         */
+
+        active = ((blitq->done_blit_handle - handle) > (1 << 23)) &&
+                ((blitq->cur_blit_handle - handle) <= (1 << 23));
+
+        if (queue && active) {
+                slot = handle - blitq->done_blit_handle + blitq->cur -1;
+                if (slot >= VIA_NUM_BLIT_SLOTS) {
+                        slot -= VIA_NUM_BLIT_SLOTS;
+                }
+                *queue = blitq->blit_queue + slot;
+        }
+
+        spin_unlock_irqrestore(&blitq->blit_lock, irqsave);
+
+        return active;
+}
+        
+/*
+ * Sync. Wait for at least three seconds for the blit to be performed.
+ */
+
+static int
+via_dmablit_sync(drm_device_t *dev, uint32_t handle, int engine) 
+{
+
+        drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private;
+        drm_via_blitq_t *blitq = dev_priv->blit_queues + engine;
+        wait_queue_head_t *queue;
+        int ret = 0;
+
+        if (via_dmablit_active(blitq, engine, handle, &queue)) {
+                DRM_WAIT_ON(ret, *queue, 3 * DRM_HZ, 
+                            !via_dmablit_active(blitq, engine, handle, NULL));
+        }
+        DRM_DEBUG("DMA blit sync handle 0x%x engine %d returned %d\n",
+                  handle, engine, ret);
+        
+        return ret;
+}
+
+
+/*
+ * A timer that regularly polls the blit engine in cases where we don't have interrupts:
+ * a) Broken hardware (typically those that don't have any video capture facility).
+ * b) Blit abort. The hardware doesn't send an interrupt when a blit is aborted.
+ * The timer and hardware IRQ's can and do work in parallel. If the hardware has
+ * irqs, it will shorten the latency somewhat.
+ */
+
+
+
+static void
+via_dmablit_timer(unsigned long data)
+{
+        drm_via_blitq_t *blitq = (drm_via_blitq_t *) data;
+        drm_device_t *dev = blitq->dev;
+        int engine = (int)
+                (blitq - ((drm_via_private_t *)dev->dev_private)->blit_queues);
+                
+        DRM_DEBUG("Polling timer called for engine %d, jiffies %lu\n", engine, 
+                  (unsigned long) jiffies);
+
+        via_dmablit_handler(dev, engine, 0);
+        
+        if (!timer_pending(&blitq->poll_timer)) {
+                blitq->poll_timer.expires = jiffies+1;
+                add_timer(&blitq->poll_timer);
+        }
+        via_dmablit_handler(dev, engine, 0);
+
+}
+
+
+
+
+/*
+ * Workqueue task that frees data and mappings associated with a blit.
+ * Also wakes up waiting processes. Each of these tasks handles one
+ * blit engine only and may not be called on each interrupt.
+ */
+
+
+static void 
+via_dmablit_workqueue(void *data)
+{
+        drm_via_blitq_t *blitq = (drm_via_blitq_t *) data;
+        drm_device_t *dev = blitq->dev;
+        unsigned long irqsave;
+        drm_via_sg_info_t *cur_sg;
+        int cur_released;
+        
+        
+        DRM_DEBUG("Workqueue task called for blit engine %ld\n",(unsigned long) 
+                  (blitq - ((drm_via_private_t *)dev->dev_private)->blit_queues));
+
+        spin_lock_irqsave(&blitq->blit_lock, irqsave);
+        
+        while(blitq->serviced != blitq->cur) {
+
+                cur_released = blitq->serviced++;
+
+                DRM_DEBUG("Releasing blit slot %d\n", cur_released);
+
+                if (blitq->serviced >= VIA_NUM_BLIT_SLOTS) 
+                        blitq->serviced = 0;
+                
+                cur_sg = blitq->blits[cur_released];
+                blitq->num_free++;
+                                
+                spin_unlock_irqrestore(&blitq->blit_lock, irqsave);
+                
+                DRM_WAKEUP(&blitq->busy_queue);
+                
+                via_free_sg_info(dev->pdev, cur_sg);
+                kfree(cur_sg);
+                
+                spin_lock_irqsave(&blitq->blit_lock, irqsave);
+        }
+
+        spin_unlock_irqrestore(&blitq->blit_lock, irqsave);
+}
+        
+
+/*
+ * Init all blit engines. Currently we use two, but some hardware have 4.
+ */
+
+
+void
+via_init_dmablit(drm_device_t *dev)
+{
+        int i,j;
+        drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private;
+        drm_via_blitq_t *blitq;
+
+        pci_set_master(dev->pdev);      
+        
+        for (i=0; i< VIA_NUM_BLIT_ENGINES; ++i) {
+                blitq = dev_priv->blit_queues + i;
+                blitq->dev = dev;
+                blitq->cur_blit_handle = 0;
+                blitq->done_blit_handle = 0;
+                blitq->head = 0;
+                blitq->cur = 0;
+                blitq->serviced = 0;
+                blitq->num_free = VIA_NUM_BLIT_SLOTS;
+                blitq->num_outstanding = 0;
+                blitq->is_active = 0;
+                blitq->aborting = 0;
+                blitq->blit_lock = SPIN_LOCK_UNLOCKED;
+                for (j=0; j<VIA_NUM_BLIT_SLOTS; ++j) {
+                        DRM_INIT_WAITQUEUE(blitq->blit_queue + j);
+                }
+                DRM_INIT_WAITQUEUE(&blitq->busy_queue);
+                INIT_WORK(&blitq->wq, via_dmablit_workqueue, blitq);
+                init_timer(&blitq->poll_timer);
+                blitq->poll_timer.function = &via_dmablit_timer;
+                blitq->poll_timer.data = (unsigned long) blitq;
+        }       
+}
+
+/*
+ * Build all info and do all mappings required for a blit.
+ */
+                
+
+static int
+via_build_sg_info(drm_device_t *dev, drm_via_sg_info_t *vsg, drm_via_dmablit_t *xfer)
+{
+        int draw = xfer->to_fb;
+        int ret = 0;
+        
+        vsg->direction = (draw) ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+        vsg->bounce_buffer = 0;
+
+        vsg->state = dr_via_sg_init;
+
+        if (xfer->num_lines <= 0 || xfer->line_length <= 0) {
+                DRM_ERROR("Zero size bitblt.\n");
+                return DRM_ERR(EINVAL);
+        }
+
+        /*
+         * Below check is a driver limitation, not a hardware one. We
+         * don't want to lock unused pages, and don't want to incoporate the
+         * extra logic of avoiding them. Make sure there are no. 
+         * (Not a big limitation anyway.)
+         */
+
+        if (((xfer->mem_stride - xfer->line_length) >= PAGE_SIZE) ||
+            (xfer->mem_stride > 2048*4)) {
+                DRM_ERROR("Too large system memory stride. Stride: %d, "
+                          "Length: %d\n", xfer->mem_stride, xfer->line_length);
+                return DRM_ERR(EINVAL);
+        }
+
+        if (xfer->num_lines > 2048) {
+                DRM_ERROR("Too many PCI DMA bitblt lines.\n");
+                return DRM_ERR(EINVAL);
+        }               
+
+        /* 
+         * we allow a negative fb stride to allow flipping of images in
+         * transfer. 
+         */
+
+        if (xfer->mem_stride < xfer->line_length ||
+                abs(xfer->fb_stride) < xfer->line_length) {
+                DRM_ERROR("Invalid frame-buffer / memory stride.\n");
+                return DRM_ERR(EINVAL);
+        }
+
+        /*
+         * A hardware bug seems to be worked around if system memory addresses start on
+         * 16 byte boundaries. This seems a bit restrictive however. VIA is contacted
+         * about this. Meanwhile, impose the following restrictions:
+         */
+
+#ifdef VIA_BUGFREE
+        if ((((unsigned long)xfer->mem_addr & 3) != ((unsigned long)xfer->fb_addr & 3)) ||
+            ((xfer->mem_stride & 3) != (xfer->fb_stride & 3))) {
+                DRM_ERROR("Invalid DRM bitblt alignment.\n");
+                return DRM_ERR(EINVAL);
+        }
+#else
+        if ((((unsigned long)xfer->mem_addr & 15) ||
+            ((unsigned long)xfer->fb_addr & 3)) || (xfer->mem_stride & 15) ||
+            (xfer->fb_stride & 3)) {
+                DRM_ERROR("Invalid DRM bitblt alignment.\n");
+                return DRM_ERR(EINVAL);
+        }       
+#endif
+
+        if (0 != (ret = via_lock_all_dma_pages(vsg, xfer))) {
+                DRM_ERROR("Could not lock DMA pages.\n");
+                via_free_sg_info(dev->pdev, vsg);
+                return ret;
+        }
+
+        via_map_blit_for_device(dev->pdev, xfer, vsg, 0);
+        if (0 != (ret = via_alloc_desc_pages(vsg))) {
+                DRM_ERROR("Could not allocate DMA descriptor pages.\n");
+                via_free_sg_info(dev->pdev, vsg);
+                return ret;
+        }
+        via_map_blit_for_device(dev->pdev, xfer, vsg, 1);
+        
+        return 0;
+}
+        
+
+/*
+ * Reserve one free slot in the blit queue. Will wait for one second for one
+ * to become available. Otherwise -EBUSY is returned.
+ */
+
+static int 
+via_dmablit_grab_slot(drm_via_blitq_t *blitq, int engine)
+{
+        int ret=0;
+        unsigned long irqsave;
+
+        DRM_DEBUG("Num free is %d\n", blitq->num_free);
+        spin_lock_irqsave(&blitq->blit_lock, irqsave);
+        while(blitq->num_free == 0) {
+                spin_unlock_irqrestore(&blitq->blit_lock, irqsave);
+
+                DRM_WAIT_ON(ret, blitq->busy_queue, DRM_HZ, blitq->num_free > 0);
+                if (ret) {
+                        return (DRM_ERR(EINTR) == ret) ? DRM_ERR(EAGAIN) : ret;
+                }
+                
+                spin_lock_irqsave(&blitq->blit_lock, irqsave);
+        }
+        
+        blitq->num_free--;
+        spin_unlock_irqrestore(&blitq->blit_lock, irqsave);
+
+        return 0;
+}
+
+/*
+ * Hand back a free slot if we changed our mind.
+ */
+
+static void 
+via_dmablit_release_slot(drm_via_blitq_t *blitq)
+{
+        unsigned long irqsave;
+
+        spin_lock_irqsave(&blitq->blit_lock, irqsave);
+        blitq->num_free++;
+        spin_unlock_irqrestore(&blitq->blit_lock, irqsave);
+        DRM_WAKEUP( &blitq->busy_queue );
+}
+
+/*
+ * Grab a free slot. Build blit info and queue a blit.
+ */
+
+
+static int 
+via_dmablit(drm_device_t *dev, drm_via_dmablit_t *xfer)  
+{
+        drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private;
+        drm_via_sg_info_t *vsg;
+        drm_via_blitq_t *blitq;
+        int ret;
+        int engine;
+        unsigned long irqsave;
+
+        if (dev_priv == NULL) {
+                DRM_ERROR("Called without initialization.\n");
+                return DRM_ERR(EINVAL);
+        }
+
+        engine = (xfer->to_fb) ? 0 : 1;
+        blitq = dev_priv->blit_queues + engine;
+        if (0 != (ret = via_dmablit_grab_slot(blitq, engine))) {
+                return ret;
+        }
+        if (NULL == (vsg = kmalloc(sizeof(*vsg), GFP_KERNEL))) {
+                via_dmablit_release_slot(blitq);
+                return DRM_ERR(ENOMEM);
+        }
+        if (0 != (ret = via_build_sg_info(dev, vsg, xfer))) {
+                via_dmablit_release_slot(blitq);
+                kfree(vsg);
+                return ret;
+        }
+        spin_lock_irqsave(&blitq->blit_lock, irqsave);
+
+        blitq->blits[blitq->head++] = vsg;
+        if (blitq->head >= VIA_NUM_BLIT_SLOTS) 
+                blitq->head = 0;
+        blitq->num_outstanding++;
+        xfer->sync.sync_handle = ++blitq->cur_blit_handle; 
+
+        spin_unlock_irqrestore(&blitq->blit_lock, irqsave);
+        xfer->sync.engine = engine;
+
+        via_dmablit_handler(dev, engine, 0);
+
+        return 0;
+}
+
+/*
+ * Sync on a previously submitted blit. Note that the X server use signals extensively, and
+ * that there is a very big proability that this IOCTL will be interrupted by a signal. In that
+ * case it returns with -EAGAIN for the signal to be delivered. 
+ * The caller should then reissue the IOCTL. This is similar to what is being done for drmGetLock().
+ */
+
+int
+via_dma_blit_sync( DRM_IOCTL_ARGS )
+{
+        drm_via_blitsync_t sync;
+        int err;
+        DRM_DEVICE;
+
+        DRM_COPY_FROM_USER_IOCTL(sync, (drm_via_blitsync_t *)data, sizeof(sync));
+        
+        if (sync.engine >= VIA_NUM_BLIT_ENGINES) 
+                return DRM_ERR(EINVAL);
+
+        err = via_dmablit_sync(dev, sync.sync_handle, sync.engine);
+
+        if (DRM_ERR(EINTR) == err)
+                err = DRM_ERR(EAGAIN);
+
+        return err;
+}
+        
+
+/*
+ * Queue a blit and hand back a handle to be used for sync. This IOCTL may be interrupted by a signal
+ * while waiting for a free slot in the blit queue. In that case it returns with -EAGAIN and should 
+ * be reissued. See the above IOCTL code.
+ */
+
+int 
+via_dma_blit( DRM_IOCTL_ARGS )
+{
+        drm_via_dmablit_t xfer;
+        int err;
+        DRM_DEVICE;
+
+        DRM_COPY_FROM_USER_IOCTL(xfer, (drm_via_dmablit_t __user *)data, sizeof(xfer));
+
+        err = via_dmablit(dev, &xfer);
+
+        DRM_COPY_TO_USER_IOCTL((void __user *)data, xfer, sizeof(xfer));
+
+        return err;
+}