Merge head 'drm-via' of master.kernel.org:/pub/scm/linux/kernel/git/airlied/drm-2.6

1 files changed, 741 insertions, 0 deletions

diff --git a/drivers/char/drm/via_dma.c b/drivers/char/drm/via_dma.c
new file mode 100644
index 00000000000..82f83945162
--- /dev/null
+++ b/drivers/char/drm/via_dma.c
@@ -0,0 +1,741 @@
+/* via_dma.c -- DMA support for the VIA Unichrome/Pro
+ * 
+ * Copyright 2003 Tungsten Graphics, Inc., Cedar Park, Texas.
+ * All Rights Reserved.
+ *
+ * Copyright 2004 Digeo, Inc., Palo Alto, CA, U.S.A.
+ * All Rights Reserved.
+ * 
+ * Copyright 2004 The Unichrome project.
+ * 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: 
+ *    Tungsten Graphics, 
+ *    Erdi Chen, 
+ *    Thomas Hellstrom.
+ */
+
+#include "drmP.h"
+#include "drm.h"
+#include "via_drm.h"
+#include "via_drv.h"
+#include "via_3d_reg.h"
+
+#define CMDBUF_ALIGNMENT_SIZE   (0x100)
+#define CMDBUF_ALIGNMENT_MASK   (0x0ff)
+
+/* defines for VIA 3D registers */
+#define VIA_REG_STATUS          0x400
+#define VIA_REG_TRANSET         0x43C
+#define VIA_REG_TRANSPACE       0x440
+
+/* VIA_REG_STATUS(0x400): Engine Status */
+#define VIA_CMD_RGTR_BUSY       0x00000080	/* Command Regulator is busy */
+#define VIA_2D_ENG_BUSY         0x00000001	/* 2D Engine is busy */
+#define VIA_3D_ENG_BUSY         0x00000002	/* 3D Engine is busy */
+#define VIA_VR_QUEUE_BUSY       0x00020000	/* Virtual Queue is busy */
+
+#define SetReg2DAGP(nReg, nData) {				\
+	*((uint32_t *)(vb)) = ((nReg) >> 2) | HALCYON_HEADER1;	\
+	*((uint32_t *)(vb) + 1) = (nData);			\
+	vb = ((uint32_t *)vb) + 2;				\
+	dev_priv->dma_low +=8;					\
+}
+
+#define via_flush_write_combine() DRM_MEMORYBARRIER() 
+
+#define VIA_OUT_RING_QW(w1,w2)			\
+	*vb++ = (w1);				\
+	*vb++ = (w2);				\
+	dev_priv->dma_low += 8; 
+
+static void via_cmdbuf_start(drm_via_private_t * dev_priv);
+static void via_cmdbuf_pause(drm_via_private_t * dev_priv);
+static void via_cmdbuf_reset(drm_via_private_t * dev_priv);
+static void via_cmdbuf_rewind(drm_via_private_t * dev_priv);
+static int via_wait_idle(drm_via_private_t * dev_priv);
+static void via_pad_cache(drm_via_private_t *dev_priv, int qwords);
+
+
+/*
+ * Free space in command buffer.
+ */
+
+static uint32_t
+via_cmdbuf_space(drm_via_private_t *dev_priv)
+{
+	uint32_t agp_base = dev_priv->dma_offset + 
+		(uint32_t) dev_priv->agpAddr;
+	uint32_t hw_addr = *(dev_priv->hw_addr_ptr) - agp_base;
+	
+	return ((hw_addr <= dev_priv->dma_low) ? 
+		(dev_priv->dma_high + hw_addr - dev_priv->dma_low) : 
+		(hw_addr - dev_priv->dma_low));
+}
+
+/*
+ * How much does the command regulator lag behind?
+ */
+
+static uint32_t
+via_cmdbuf_lag(drm_via_private_t *dev_priv)
+{
+	uint32_t agp_base = dev_priv->dma_offset + 
+		(uint32_t) dev_priv->agpAddr;
+	uint32_t hw_addr = *(dev_priv->hw_addr_ptr) - agp_base;
+	
+	return ((hw_addr <= dev_priv->dma_low) ? 
+		(dev_priv->dma_low - hw_addr) : 
+		(dev_priv->dma_wrap + dev_priv->dma_low - hw_addr));
+}
+
+/*
+ * Check that the given size fits in the buffer, otherwise wait.
+ */
+
+static inline int
+via_cmdbuf_wait(drm_via_private_t * dev_priv, unsigned int size)
+{
+	uint32_t agp_base = dev_priv->dma_offset + (uint32_t) dev_priv->agpAddr;
+	uint32_t cur_addr, hw_addr, next_addr;
+	volatile uint32_t *hw_addr_ptr;
+	uint32_t count;
+	hw_addr_ptr = dev_priv->hw_addr_ptr;
+	cur_addr = dev_priv->dma_low;
+	next_addr = cur_addr + size + 512*1024;
+	count = 1000000;
+	do {
+	        hw_addr = *hw_addr_ptr - agp_base;
+		if (count-- == 0) {
+			DRM_ERROR("via_cmdbuf_wait timed out hw %x cur_addr %x next_addr %x\n",
+				  hw_addr, cur_addr, next_addr);
+			return -1;
+		}
+	} while ((cur_addr < hw_addr) && (next_addr >= hw_addr));
+	return 0;
+}
+
+
+/*
+ * Checks whether buffer head has reach the end. Rewind the ring buffer
+ * when necessary.
+ *
+ * Returns virtual pointer to ring buffer.
+ */
+
+static inline uint32_t *via_check_dma(drm_via_private_t * dev_priv,
+				      unsigned int size)
+{
+	if ((dev_priv->dma_low + size + 4*CMDBUF_ALIGNMENT_SIZE) > dev_priv->dma_high) {
+		via_cmdbuf_rewind(dev_priv);
+	}
+	if (via_cmdbuf_wait(dev_priv, size) != 0) {
+		return NULL;
+	}
+
+	return (uint32_t *) (dev_priv->dma_ptr + dev_priv->dma_low);
+}
+
+int via_dma_cleanup(drm_device_t * dev)
+{
+	if (dev->dev_private) {
+		drm_via_private_t *dev_priv =
+			(drm_via_private_t *) dev->dev_private;
+
+		if (dev_priv->ring.virtual_start) {
+			via_cmdbuf_reset(dev_priv);
+
+			drm_core_ioremapfree(&dev_priv->ring.map, dev);
+			dev_priv->ring.virtual_start = NULL;
+		}
+
+	}
+
+	return 0;
+}
+
+static int via_initialize(drm_device_t * dev,
+			  drm_via_private_t * dev_priv,
+			  drm_via_dma_init_t * init)
+{
+	if (!dev_priv || !dev_priv->mmio) {
+		DRM_ERROR("via_dma_init called before via_map_init\n");
+		return DRM_ERR(EFAULT);
+	}
+
+	if (dev_priv->ring.virtual_start != NULL) {
+		DRM_ERROR("%s called again without calling cleanup\n",
+			  __FUNCTION__);
+		return DRM_ERR(EFAULT);
+	}
+
+	if (!dev->agp || !dev->agp->base) {
+		DRM_ERROR("%s called with no agp memory available\n", 
+			  __FUNCTION__);
+		return DRM_ERR(EFAULT);
+	}
+
+	dev_priv->ring.map.offset = dev->agp->base + init->offset;
+	dev_priv->ring.map.size = init->size;
+	dev_priv->ring.map.type = 0;
+	dev_priv->ring.map.flags = 0;
+	dev_priv->ring.map.mtrr = 0;
+
+	drm_core_ioremap(&dev_priv->ring.map, dev);
+
+	if (dev_priv->ring.map.handle == NULL) {
+		via_dma_cleanup(dev);
+		DRM_ERROR("can not ioremap virtual address for"
+			  " ring buffer\n");
+		return DRM_ERR(ENOMEM);
+	}
+
+	dev_priv->ring.virtual_start = dev_priv->ring.map.handle;
+
+	dev_priv->dma_ptr = dev_priv->ring.virtual_start;
+	dev_priv->dma_low = 0;
+	dev_priv->dma_high = init->size;
+	dev_priv->dma_wrap = init->size;
+	dev_priv->dma_offset = init->offset;
+	dev_priv->last_pause_ptr = NULL;
+	dev_priv->hw_addr_ptr = dev_priv->mmio->handle + init->reg_pause_addr;
+
+	via_cmdbuf_start(dev_priv);
+
+	return 0;
+}
+
+int via_dma_init(DRM_IOCTL_ARGS)
+{
+	DRM_DEVICE;
+	drm_via_private_t *dev_priv = (drm_via_private_t *) dev->dev_private;
+	drm_via_dma_init_t init;
+	int retcode = 0;
+
+	DRM_COPY_FROM_USER_IOCTL(init, (drm_via_dma_init_t *) data,
+				 sizeof(init));
+
+	switch (init.func) {
+	case VIA_INIT_DMA:
+		if (!capable(CAP_SYS_ADMIN))
+			retcode = DRM_ERR(EPERM);
+		else
+			retcode = via_initialize(dev, dev_priv, &init);
+		break;
+	case VIA_CLEANUP_DMA:
+		if (!capable(CAP_SYS_ADMIN))
+			retcode = DRM_ERR(EPERM);
+		else
+			retcode = via_dma_cleanup(dev);
+		break;
+        case VIA_DMA_INITIALIZED:
+		retcode = (dev_priv->ring.virtual_start != NULL) ? 
+			0: DRM_ERR( EFAULT );
+	        break;
+	default:
+		retcode = DRM_ERR(EINVAL);
+		break;
+	}
+
+	return retcode;
+}
+
+
+
+static int via_dispatch_cmdbuffer(drm_device_t * dev, drm_via_cmdbuffer_t * cmd)
+{
+	drm_via_private_t *dev_priv;
+	uint32_t *vb;
+	int ret;
+
+	dev_priv = (drm_via_private_t *) dev->dev_private;
+
+	if (dev_priv->ring.virtual_start == NULL) {
+		DRM_ERROR("%s called without initializing AGP ring buffer.\n",
+			  __FUNCTION__);
+		return DRM_ERR(EFAULT);
+	}
+
+	if (cmd->size > VIA_PCI_BUF_SIZE) {
+		return DRM_ERR(ENOMEM);
+	} 
+
+
+	if (DRM_COPY_FROM_USER(dev_priv->pci_buf, cmd->buf, cmd->size))
+		return DRM_ERR(EFAULT);
+
+	/*
+	 * Running this function on AGP memory is dead slow. Therefore
+	 * we run it on a temporary cacheable system memory buffer and
+	 * copy it to AGP memory when ready.
+	 */
+
+		
+	if ((ret = via_verify_command_stream((uint32_t *)dev_priv->pci_buf, cmd->size, dev, 1))) {
+		return ret;
+	}
+       	
+	
+	vb = via_check_dma(dev_priv, (cmd->size < 0x100) ? 0x102 : cmd->size);
+	if (vb == NULL) {
+		return DRM_ERR(EAGAIN);
+	}
+
+	memcpy(vb, dev_priv->pci_buf, cmd->size);
+	
+	dev_priv->dma_low += cmd->size;
+
+	/*
+	 * Small submissions somehow stalls the CPU. (AGP cache effects?)
+	 * pad to greater size.
+	 */
+
+	if (cmd->size < 0x100)
+	  via_pad_cache(dev_priv,(0x100 - cmd->size) >> 3);
+	via_cmdbuf_pause(dev_priv);
+
+	return 0;
+}
+
+int via_driver_dma_quiescent(drm_device_t * dev)
+{
+	drm_via_private_t *dev_priv = dev->dev_private;
+
+	if (!via_wait_idle(dev_priv)) {
+		return DRM_ERR(EBUSY);
+	}
+	return 0;
+}
+
+int via_flush_ioctl(DRM_IOCTL_ARGS)
+{
+	DRM_DEVICE;
+
+	LOCK_TEST_WITH_RETURN( dev, filp );
+
+	return via_driver_dma_quiescent(dev);
+}
+
+int via_cmdbuffer(DRM_IOCTL_ARGS)
+{
+	DRM_DEVICE;
+	drm_via_cmdbuffer_t cmdbuf;
+	int ret;
+
+	LOCK_TEST_WITH_RETURN( dev, filp );
+
+	DRM_COPY_FROM_USER_IOCTL(cmdbuf, (drm_via_cmdbuffer_t *) data,
+				 sizeof(cmdbuf));
+
+	DRM_DEBUG("via cmdbuffer, buf %p size %lu\n", cmdbuf.buf, cmdbuf.size);
+
+	ret = via_dispatch_cmdbuffer(dev, &cmdbuf);
+	if (ret) {
+		return ret;
+	}
+
+	return 0;
+}
+
+extern int 
+via_parse_command_stream(drm_device_t *dev, const uint32_t * buf, unsigned int size);
+static int via_dispatch_pci_cmdbuffer(drm_device_t * dev,
+				      drm_via_cmdbuffer_t * cmd)
+{
+	drm_via_private_t *dev_priv = dev->dev_private;
+	int ret;
+
+	if (cmd->size > VIA_PCI_BUF_SIZE) {
+		return DRM_ERR(ENOMEM);
+	} 
+	if (DRM_COPY_FROM_USER(dev_priv->pci_buf, cmd->buf, cmd->size))
+		return DRM_ERR(EFAULT);
+	
+	if ((ret = via_verify_command_stream((uint32_t *)dev_priv->pci_buf, cmd->size, dev, 0))) {
+		return ret;
+	}
+	
+	ret = via_parse_command_stream(dev, (const uint32_t *)dev_priv->pci_buf, cmd->size);
+	return ret;
+}
+
+int via_pci_cmdbuffer(DRM_IOCTL_ARGS)
+{
+	DRM_DEVICE;
+	drm_via_cmdbuffer_t cmdbuf;
+	int ret;
+
+	LOCK_TEST_WITH_RETURN( dev, filp );
+
+	DRM_COPY_FROM_USER_IOCTL(cmdbuf, (drm_via_cmdbuffer_t *) data,
+				 sizeof(cmdbuf));
+
+	DRM_DEBUG("via_pci_cmdbuffer, buf %p size %lu\n", cmdbuf.buf,
+		  cmdbuf.size);
+
+	ret = via_dispatch_pci_cmdbuffer(dev, &cmdbuf);
+	if (ret) {
+		return ret;
+	}
+
+	return 0;
+}
+
+
+static inline uint32_t *via_align_buffer(drm_via_private_t * dev_priv,
+					 uint32_t * vb, int qw_count)
+{
+        for (; qw_count > 0; --qw_count) {
+		VIA_OUT_RING_QW(HC_DUMMY, HC_DUMMY);
+	}
+	return vb;
+}
+
+
+/*
+ * This function is used internally by ring buffer mangement code.
+ *
+ * Returns virtual pointer to ring buffer.
+ */
+static inline uint32_t *via_get_dma(drm_via_private_t * dev_priv)
+{
+	return (uint32_t *) (dev_priv->dma_ptr + dev_priv->dma_low);
+}
+
+/*
+ * Hooks a segment of data into the tail of the ring-buffer by
+ * modifying the pause address stored in the buffer itself. If
+ * the regulator has already paused, restart it.
+ */
+static int via_hook_segment(drm_via_private_t *dev_priv,
+			    uint32_t pause_addr_hi, uint32_t pause_addr_lo,
+			    int no_pci_fire)
+{
+	int paused, count;
+	volatile uint32_t *paused_at = dev_priv->last_pause_ptr;
+
+	via_flush_write_combine();
+	while(! *(via_get_dma(dev_priv)-1));
+	*dev_priv->last_pause_ptr = pause_addr_lo;
+	via_flush_write_combine();
+
+	/*
+	 * The below statement is inserted to really force the flush.
+	 * Not sure it is needed.
+	 */
+
+	while(! *dev_priv->last_pause_ptr);
+	dev_priv->last_pause_ptr = via_get_dma(dev_priv) - 1;
+	while(! *dev_priv->last_pause_ptr);
+
+
+	paused = 0;
+	count = 20; 
+
+	while (!(paused = (VIA_READ(0x41c) & 0x80000000)) && count--);
+	if ((count <= 8) && (count >= 0)) {
+		uint32_t rgtr, ptr;
+		rgtr = *(dev_priv->hw_addr_ptr);
+		ptr = ((char *)dev_priv->last_pause_ptr - dev_priv->dma_ptr) + 
+			dev_priv->dma_offset + (uint32_t) dev_priv->agpAddr + 4 - 
+			CMDBUF_ALIGNMENT_SIZE;
+		if (rgtr <= ptr) {
+			DRM_ERROR("Command regulator\npaused at count %d, address %x, "
+				  "while current pause address is %x.\n"
+				  "Please mail this message to "
+				  "<unichrome-devel@lists.sourceforge.net>\n",
+				  count, rgtr, ptr);
+		}
+	}
+		
+	if (paused && !no_pci_fire) {
+	        uint32_t rgtr,ptr;
+		uint32_t ptr_low;
+
+		count = 1000000;
+		while ((VIA_READ(VIA_REG_STATUS) & VIA_CMD_RGTR_BUSY) && count--);
+		
+		rgtr = *(dev_priv->hw_addr_ptr);
+		ptr = ((char *)paused_at - dev_priv->dma_ptr) + 
+			dev_priv->dma_offset + (uint32_t) dev_priv->agpAddr + 4;
+		
+
+		ptr_low = (ptr > 3*CMDBUF_ALIGNMENT_SIZE) ? 
+			ptr - 3*CMDBUF_ALIGNMENT_SIZE : 0;
+		if (rgtr <= ptr && rgtr >= ptr_low) {
+			VIA_WRITE(VIA_REG_TRANSET, (HC_ParaType_PreCR << 16));
+			VIA_WRITE(VIA_REG_TRANSPACE, pause_addr_hi);
+			VIA_WRITE(VIA_REG_TRANSPACE, pause_addr_lo);
+		} 
+	}
+	return paused;
+}
+
+
+
+static int via_wait_idle(drm_via_private_t * dev_priv)
+{
+	int count = 10000000;
+	while (count-- && (VIA_READ(VIA_REG_STATUS) &
+			   (VIA_CMD_RGTR_BUSY | VIA_2D_ENG_BUSY |
+			    VIA_3D_ENG_BUSY))) ;
+	return count;
+}
+
+static uint32_t *via_align_cmd(drm_via_private_t * dev_priv, uint32_t cmd_type,
+			       uint32_t addr, uint32_t *cmd_addr_hi, 
+			       uint32_t *cmd_addr_lo,
+			       int skip_wait)
+{
+	uint32_t agp_base;
+	uint32_t cmd_addr, addr_lo, addr_hi;
+	uint32_t *vb;
+	uint32_t qw_pad_count;
+
+	if (!skip_wait)
+		via_cmdbuf_wait(dev_priv, 2*CMDBUF_ALIGNMENT_SIZE);
+
+	vb = via_get_dma(dev_priv);
+	VIA_OUT_RING_QW( HC_HEADER2 | ((VIA_REG_TRANSET >> 2) << 12) |
+			 (VIA_REG_TRANSPACE >> 2), HC_ParaType_PreCR << 16); 
+	agp_base = dev_priv->dma_offset + (uint32_t) dev_priv->agpAddr;
+	qw_pad_count = (CMDBUF_ALIGNMENT_SIZE >> 3) -
+		((dev_priv->dma_low & CMDBUF_ALIGNMENT_MASK) >> 3);
+
+	
+	cmd_addr = (addr) ? addr : 
+		agp_base + dev_priv->dma_low - 8 + (qw_pad_count << 3);
+	addr_lo = ((HC_SubA_HAGPBpL << 24) | (cmd_type & HC_HAGPBpID_MASK) |
+		   (cmd_addr & HC_HAGPBpL_MASK));
+	addr_hi = ((HC_SubA_HAGPBpH << 24) | (cmd_addr >> 24));
+
+	vb = via_align_buffer(dev_priv, vb, qw_pad_count - 1);
+	VIA_OUT_RING_QW(*cmd_addr_hi = addr_hi, 
+			*cmd_addr_lo = addr_lo);
+	return vb;
+}
+
+
+
+
+static void via_cmdbuf_start(drm_via_private_t * dev_priv)
+{
+	uint32_t pause_addr_lo, pause_addr_hi;
+	uint32_t start_addr, start_addr_lo;
+	uint32_t end_addr, end_addr_lo;
+	uint32_t command;
+	uint32_t agp_base;
+
+
+	dev_priv->dma_low = 0;
+
+	agp_base = dev_priv->dma_offset + (uint32_t) dev_priv->agpAddr;
+	start_addr = agp_base;
+	end_addr = agp_base + dev_priv->dma_high;
+
+	start_addr_lo = ((HC_SubA_HAGPBstL << 24) | (start_addr & 0xFFFFFF));
+	end_addr_lo = ((HC_SubA_HAGPBendL << 24) | (end_addr & 0xFFFFFF));
+	command = ((HC_SubA_HAGPCMNT << 24) | (start_addr >> 24) |
+		   ((end_addr & 0xff000000) >> 16));
+
+	dev_priv->last_pause_ptr = 
+		via_align_cmd(dev_priv, HC_HAGPBpID_PAUSE, 0, 
+			      &pause_addr_hi, & pause_addr_lo, 1) - 1;
+
+	via_flush_write_combine();
+	while(! *dev_priv->last_pause_ptr);
+
+	VIA_WRITE(VIA_REG_TRANSET, (HC_ParaType_PreCR << 16));
+	VIA_WRITE(VIA_REG_TRANSPACE, command);
+	VIA_WRITE(VIA_REG_TRANSPACE, start_addr_lo);
+	VIA_WRITE(VIA_REG_TRANSPACE, end_addr_lo);
+
+	VIA_WRITE(VIA_REG_TRANSPACE, pause_addr_hi);
+	VIA_WRITE(VIA_REG_TRANSPACE, pause_addr_lo);
+
+	VIA_WRITE(VIA_REG_TRANSPACE, command | HC_HAGPCMNT_MASK);
+}
+
+static void via_pad_cache(drm_via_private_t *dev_priv, int qwords)
+{
+	uint32_t *vb;
+
+	via_cmdbuf_wait(dev_priv, qwords + 2);
+	vb = via_get_dma(dev_priv);
+	VIA_OUT_RING_QW( HC_HEADER2, HC_ParaType_NotTex << 16);
+	via_align_buffer(dev_priv,vb,qwords);
+}
+
+static inline void via_dummy_bitblt(drm_via_private_t * dev_priv)
+{
+	uint32_t *vb = via_get_dma(dev_priv);
+	SetReg2DAGP(0x0C, (0 | (0 << 16)));
+	SetReg2DAGP(0x10, 0 | (0 << 16));
+	SetReg2DAGP(0x0, 0x1 | 0x2000 | 0xAA000000); 
+}
+
+
+static void via_cmdbuf_jump(drm_via_private_t * dev_priv)
+{
+	uint32_t agp_base;
+	uint32_t pause_addr_lo, pause_addr_hi;
+	uint32_t jump_addr_lo, jump_addr_hi;
+	volatile uint32_t *last_pause_ptr;
+	uint32_t dma_low_save1, dma_low_save2;
+
+	agp_base = dev_priv->dma_offset + (uint32_t) dev_priv->agpAddr;
+	via_align_cmd(dev_priv,  HC_HAGPBpID_JUMP, 0, &jump_addr_hi, 
+		      &jump_addr_lo, 0);
+	
+	dev_priv->dma_wrap = dev_priv->dma_low;
+
+
+	/*
+	 * Wrap command buffer to the beginning.
+	 */
+
+	dev_priv->dma_low = 0;
+	if (via_cmdbuf_wait(dev_priv, CMDBUF_ALIGNMENT_SIZE) != 0) {
+		DRM_ERROR("via_cmdbuf_jump failed\n");
+	}
+
+	via_dummy_bitblt(dev_priv);
+	via_dummy_bitblt(dev_priv); 
+
+	last_pause_ptr = via_align_cmd(dev_priv,  HC_HAGPBpID_PAUSE, 0, &pause_addr_hi, 
+				       &pause_addr_lo, 0) -1;
+	via_align_cmd(dev_priv,  HC_HAGPBpID_PAUSE, 0, &pause_addr_hi, 
+		      &pause_addr_lo, 0);
+
+	*last_pause_ptr = pause_addr_lo;
+	dma_low_save1 = dev_priv->dma_low;
+
+	/*
+	 * Now, set a trap that will pause the regulator if it tries to rerun the old
+	 * command buffer. (Which may happen if via_hook_segment detecs a command regulator pause
+	 * and reissues the jump command over PCI, while the regulator has already taken the jump
+	 * and actually paused at the current buffer end).
+	 * There appears to be no other way to detect this condition, since the hw_addr_pointer
+	 * does not seem to get updated immediately when a jump occurs.
+	 */
+
+	last_pause_ptr = via_align_cmd(dev_priv,  HC_HAGPBpID_PAUSE, 0, &pause_addr_hi, 
+				       &pause_addr_lo, 0) -1;
+	via_align_cmd(dev_priv,  HC_HAGPBpID_PAUSE, 0, &pause_addr_hi, 
+		      &pause_addr_lo, 0);
+	*last_pause_ptr = pause_addr_lo;
+
+	dma_low_save2 = dev_priv->dma_low;
+	dev_priv->dma_low = dma_low_save1;	
+	via_hook_segment( dev_priv, jump_addr_hi, jump_addr_lo, 0);
+	dev_priv->dma_low = dma_low_save2;
+	via_hook_segment( dev_priv, pause_addr_hi, pause_addr_lo, 0);
+}
+
+
+static void via_cmdbuf_rewind(drm_via_private_t * dev_priv)
+{
+	via_cmdbuf_jump(dev_priv); 
+}
+
+static void via_cmdbuf_flush(drm_via_private_t * dev_priv, uint32_t cmd_type)
+{
+	uint32_t pause_addr_lo, pause_addr_hi;
+
+	via_align_cmd(dev_priv, cmd_type, 0, &pause_addr_hi, &pause_addr_lo, 0);
+	via_hook_segment( dev_priv, pause_addr_hi, pause_addr_lo, 0);
+}
+
+
+static void via_cmdbuf_pause(drm_via_private_t * dev_priv)
+{
+	via_cmdbuf_flush(dev_priv, HC_HAGPBpID_PAUSE);
+}
+
+static void via_cmdbuf_reset(drm_via_private_t * dev_priv)
+{
+	via_cmdbuf_flush(dev_priv, HC_HAGPBpID_STOP);
+	via_wait_idle(dev_priv);
+}
+
+/*
+ * User interface to the space and lag functions.
+ */
+
+int 
+via_cmdbuf_size(DRM_IOCTL_ARGS)
+{
+	DRM_DEVICE;
+	drm_via_cmdbuf_size_t d_siz;
+	int ret = 0;
+	uint32_t tmp_size, count;
+	drm_via_private_t *dev_priv;
+
+	DRM_DEBUG("via cmdbuf_size\n");
+	LOCK_TEST_WITH_RETURN( dev, filp );
+
+	dev_priv = (drm_via_private_t *) dev->dev_private;
+
+	if (dev_priv->ring.virtual_start == NULL) {
+		DRM_ERROR("%s called without initializing AGP ring buffer.\n",
+			  __FUNCTION__);
+		return DRM_ERR(EFAULT);
+	}
+
+	DRM_COPY_FROM_USER_IOCTL(d_siz, (drm_via_cmdbuf_size_t *) data,
+				 sizeof(d_siz));
+
+
+	count = 1000000;
+	tmp_size = d_siz.size;
+	switch(d_siz.func) {
+	case VIA_CMDBUF_SPACE:
+		while (((tmp_size = via_cmdbuf_space(dev_priv)) < d_siz.size) && count--) {
+			if (!d_siz.wait) {
+				break;
+			}
+		}
+		if (!count) {
+			DRM_ERROR("VIA_CMDBUF_SPACE timed out.\n");
+			ret = DRM_ERR(EAGAIN);
+		}
+		break;
+	case VIA_CMDBUF_LAG:
+		while (((tmp_size = via_cmdbuf_lag(dev_priv)) > d_siz.size) && count--) {
+			if (!d_siz.wait) {
+				break;
+			}
+		}
+		if (!count) {
+			DRM_ERROR("VIA_CMDBUF_LAG timed out.\n");
+			ret = DRM_ERR(EAGAIN);
+		}
+		break;
+	default:
+		ret = DRM_ERR(EFAULT);
+	}
+	d_siz.size = tmp_size;
+
+	DRM_COPY_TO_USER_IOCTL((drm_via_cmdbuf_size_t *) data, d_siz,
+			       sizeof(d_siz));
+	return ret;
+}