haiku/src/add-ons/kernel/bus_managers/scsi/dma_buffer.c

/*
** Copyright 2002/03, Thomas Kurschel. All rights reserved.
** Distributed under the terms of the OpenBeOS License.
*/

/*
	Part of Open SCSI bus manager

	DMA buffer handling.

	If the peripheral driver hasn't made sure that the data of a request 
	is DMA safe, we check that and copy data to a buffer if needed.
	The buffer is enlarged on demand and destroyed after a time-out
	by a daemon. Obviously, it's a good idea to avoid all this, therefore 
	blkman takes care of that for read/write requests.
	
	To be able to copy data back after the request was finished, we need a 
	S/G list to the original data as the copying is done in a different
	thread/process context (namely the service thread).
	
	Currently, there is only one buffer per device; in the future,
	we may support multiple buffers, especially if we want to support
	more then 4 GB memory, which leads to trouble with 32-bit PCI cards.
*/


#include "scsi_internal.h"
#include "KernelExport_ext.h"
#include <string.h>


// check whether S/G list of request is supported DMA controller
static bool
is_sg_list_dma_safe(scsi_ccb *request) 
{
	scsi_bus_info *bus = request->bus;
	const physical_entry *sg_list = request->sg_list;
	uint32 sg_count = request->sg_cnt;
	uint32 dma_boundary = bus->dma_params.dma_boundary;
	uint32 alignment = bus->dma_params.alignment;
	uint32 max_sg_block_size = bus->dma_params.max_sg_block_size;
	uint32 cur_idx;
	
	// not too many S/G list entries
	if( sg_count > bus->dma_params.max_sg_blocks ) {
		SHOW_FLOW0( 0, "S/G-list too long" );
		return false;
	}
		
	// if there are no further restrictions - be happy
	if (dma_boundary == ~0UL && alignment == 0 && max_sg_block_size == 0)
		return true;

	// argh - controller is a bit picky, so make sure he likes us
	for( cur_idx = sg_count; cur_idx >= 1; --cur_idx, ++sg_list ) {
		addr_t max_len;

		// calculate space upto next dma boundary crossing and
		// verify that it isn't crossed
		max_len = (dma_boundary + 1) - 
			((addr_t)sg_list->address & dma_boundary);
			
		if( max_len < sg_list->size ) {
			SHOW_FLOW( 0, "S/G-entry crosses DMA boundary @0x%x", 
				(int)sg_list->address + (int)max_len);
			return false;
		}
		
		// check both begin and end of entry for alignment
		if( ((addr_t)sg_list->address & alignment) != 0 ) {
			SHOW_FLOW( 0, "S/G-entry has bad alignment @0x%x",
				(int)sg_list->address );
			return false;
		}
		
		if( (((addr_t)sg_list->address + sg_list->size) & alignment) != 0 ) {
			SHOW_FLOW( 0, "end of S/G-entry has bad alignment @0x%x",
				(int)sg_list->address + (int)sg_list->size );
			return false;
		}
		
		// verify entry size
		if( sg_list->size > max_sg_block_size ) {
			SHOW_FLOW( 0, "S/G-entry is too long (%d/%d bytes)",
				(int)sg_list->size, (int)max_sg_block_size );
			return false;
		}
	}
	
	return true;
}


/** copy data from/to DMA buffer */

static bool
scsi_copy_dma_buffer(scsi_ccb *request, uint32 size, bool to_buffer)
{
	dma_buffer *buffer = request->dma_buffer;
	const physical_entry *sg_list = buffer->sg_list_orig;
	uint32 num_vecs = buffer->sg_cnt_orig;
	char *buffer_data = buffer->address;

	SHOW_FLOW(0, "to_buffer=%d, %d bytes", to_buffer, (int)size);

	// survive even if controller returned invalid data size
	size = min(size, request->data_len);

	// we have to use S/G list to original data; the DMA buffer
	// was allocated in kernel and is thus visible even if the thread
	// was changed
	for( ; size > 0 && num_vecs > 0; ++sg_list, --num_vecs ) {
		size_t bytes;
		void *virt_addr;
		
		bytes = min( size, sg_list->size );

		if( map_mainmemory( (addr_t)sg_list->address, &virt_addr ) != B_OK ) 
			return false;
				
		if( to_buffer )
			memcpy( buffer_data, virt_addr, bytes );
		else
			memcpy( virt_addr, buffer_data, bytes );
		
		unmap_mainmemory( virt_addr );
		
		buffer_data += bytes;
	}
		
	return true;
}


// get log2
static int log2( uint32 x )
{
	int y;
	
	for( y = 31; y >= 0; --y )
		if( x == ((uint32)1 << y) )
			break;
			
	return y;
}

static void scsi_free_dma_buffer( dma_buffer *buffer )
{
	if( buffer->area > 0 ) {
		SHOW_FLOW0( 0, "Destroying buffer" );

		delete_area( buffer->area );
		buffer->area = 0;
		buffer->size = 0;
	}
	
	if( buffer->sg_list_area > 0 ) {
		delete_area( buffer->sg_list_area );
		buffer->sg_list_area = 0;
	}
}


/**	allocate dma buffer for given device, deleting old one
 *	size - buffer size in bytes
 */

static bool
scsi_alloc_dma_buffer(dma_buffer *buffer, dma_params *dma_params, uint32 size)
{
	size_t sg_list_size, sg_list_entries;
	
	// free old buffer first	
	scsi_free_dma_buffer( buffer );

	// just in case alignment is redicuously huge
	size = (size + dma_params->alignment) & ~dma_params->alignment;
	
	size = (size + B_PAGE_SIZE - 1) & ~(B_PAGE_SIZE - 1);
	
	// calculate worst case number of S/G entries, i.e. if they are non-continuous;
	// there is a controller limit and a limit by our own S/G manager to check
	if( size / B_PAGE_SIZE > dma_params->max_sg_blocks || 
		size / B_PAGE_SIZE > MAX_TEMP_SG_FRAGMENTS ) 
	{
		uint32 boundary = dma_params->dma_boundary;
		uchar *dma_buffer_address_unaligned;
		
		// alright - a contiguous buffer is required to keep S/G table short
		SHOW_INFO( 0, "need to setup contiguous DMA buffer of size %d", 
			(int)size );


		// verify that we don't get problems with dma boundary
		if (boundary != ~0UL) {
			if( size > boundary + 1 ) {
				SHOW_ERROR( 2, "data is longer then maximum DMA transfer len (%d/%d bytes)", 
					(int)size, (int)boundary + 1 );
				return false;
			}
		
			// round up to next power of two and allocate a buffer double the 
			// needed size so we can cut out an area that doesn't cross 
			// dma boundary
			size = (1 << log2( size )) * 2;
		}
		
		buffer->area = create_area( "DMA buffer", 
			(void **)&dma_buffer_address_unaligned, 
			B_ANY_KERNEL_ADDRESS, size,
			B_FULL_LOCK | B_CONTIGUOUS, 0 );
		if( buffer->area < 0 ) {
			SHOW_ERROR( 2, "Cannot create contignous DMA buffer of %d bytes", 
				(int)size );
			return false;
		}

		if (boundary != ~0UL) {
			uchar *next_boundary;

			// boundary case: cut out piece aligned on "size"
			buffer->address = (uchar *)(
				((addr_t)dma_buffer_address_unaligned + size - 1) & ~(size - 1));
		
			// determine how many bytes are available until next DMA boundary
			next_boundary = (uchar *)(((addr_t)buffer->address + boundary - 1) &
				~(boundary - 1));

			// adjust next boundary if outside allocated area
			if( next_boundary > dma_buffer_address_unaligned + size )
				next_boundary = dma_buffer_address_unaligned + size;
				
			buffer->size = next_boundary - buffer->address;
		} else {
			// non-boundary case: use buffer directly
			buffer->address = dma_buffer_address_unaligned;
			buffer->size = size;
		}
	} else {
		// we can live with a fragmented buffer - very nice
		buffer->area = create_area( "DMA buffer", 
			(void **)&buffer->address, 
			B_ANY_KERNEL_ADDRESS, size,
			B_FULL_LOCK, 0 );
		if( buffer->area < 0 ) {
			SHOW_ERROR( 2, "Cannot create DMA buffer of %d bytes", 
				(int)size );
			return false;
		}
		
		buffer->size = size;
	}

	// create S/G list	
	// worst case is one entry per page, and size is page-aligned
	sg_list_size = buffer->size / B_PAGE_SIZE * sizeof( physical_entry );
	// create_area has page-granularity
	sg_list_size = (sg_list_size + B_PAGE_SIZE - 1) & ~(B_PAGE_SIZE - 1);
	
	buffer->sg_list_area = create_area( "DMA buffer S/G table",
		(void **)&buffer->sg_list,
		B_ANY_KERNEL_ADDRESS, sg_list_size,
		B_FULL_LOCK, 0 );
	if( buffer->sg_list_area < 0 ) {
		SHOW_ERROR( 2, "Cannot craete DMA buffer S/G list of %d bytes",
			(int)sg_list_size );
			
		delete_area( buffer->area );
		buffer->area = 0;
		return false;
	}
	
	sg_list_entries = sg_list_size / sizeof( physical_entry );

	{
		size_t mapped_len;
		status_t res;
		iovec vec = {
			buffer->address,
			buffer->size
		};
		
		res = get_iovec_memory_map( 
			&vec, 1, 0, buffer->size, 
			buffer->sg_list, sg_list_entries, &buffer->sg_cnt, 
			&mapped_len );
			
		if( res != B_OK || mapped_len != buffer->size ) {
			SHOW_ERROR( 0, "Error creating S/G list for DMA buffer (%s; wanted %d, got %d bytes)",
				strerror( res ), (int)mapped_len, (int)buffer->size );
		}
	}
	
	return true;
}

static void scsi_free_dma_buffer_sg_orig( dma_buffer *buffer )
{
	if( buffer->sg_orig > 0 ) {
		delete_area( buffer->sg_orig );
		buffer->sg_orig = 0;
		buffer->sg_cnt_max_orig = 0;
	}
}


// allocate S/G list to original data
static bool scsi_alloc_dma_buffer_sg_orig( dma_buffer *buffer, int size )
{
	// free old list first	
	scsi_free_dma_buffer_sg_orig( buffer );
	
	size = (size * sizeof( physical_entry ) + B_PAGE_SIZE - 1) & ~(B_PAGE_SIZE - 1);
	
	buffer->sg_orig = create_area( "S/G to original data", 
		(void **)&buffer->sg_list_orig, 
		B_ANY_KERNEL_ADDRESS, size,
		B_NO_LOCK, 0 );
	if( buffer->sg_orig < 0 ) {
		SHOW_ERROR( 2, "Cannot S/G list buffer to original data of %d bytes", 
			(int)size );
		return false;
	}
	
	buffer->sg_cnt_max_orig = size / sizeof( physical_entry );
	
	SHOW_INFO( 3, "Got up to %d S/G entries to original data",
		(int)buffer->sg_cnt_max_orig );

	return true;
}


// helper: dump S/G table
static void dump_sg_table( const physical_entry *sg_list,
	uint32 sg_list_count )
{
	uint32 cur_idx;
	
	SHOW_FLOW( 0, "count=%d", (int)sg_list_count );
	
	for( cur_idx = sg_list_count; cur_idx >= 1; --cur_idx, ++sg_list ) {
		SHOW_FLOW( 0, "addr=%x, size=%d", (int)sg_list->address,
			(int)sg_list->size );
	}
}


// compose S/G list to original data of request
static bool scsi_dma_buffer_compose_sg_orig( dma_buffer *buffer, scsi_ccb *request )
{
	// enlarge buffer is required
	if( buffer->sg_cnt_max_orig < request->sg_cnt ) {
		if( !scsi_alloc_dma_buffer_sg_orig( buffer, request->sg_cnt ))
			return false;
	}
	
	SHOW_FLOW0( 0, "copy S/G list" );
	
	memcpy( buffer->sg_list_orig, request->sg_list, 
		request->sg_cnt * sizeof( physical_entry ));
		
	buffer->sg_cnt_orig = request->sg_cnt;
	return true;		
}


// init DMA buffer and copy data to it if required
// note: S/G list of request must already be setup
bool scsi_get_dma_buffer( scsi_ccb *request )
{
	scsi_device_info *device = request->device;
	dma_buffer *buffer;
	
	request->buffered = false;

	// perhaps we have luck and no buffering is needed
	if( is_sg_list_dma_safe( request ))		
		return true;
		
	SHOW_FLOW0( 0, "Buffer is not DMA safe" );
	
	dump_sg_table( request->sg_list, request->sg_cnt );

	// only one buffer at a time	
	acquire_sem( device->dma_buffer_owner );
	
	// make sure, clean-up daemon doesn't bother us
	ACQUIRE_BEN( &device->dma_buffer_lock );
	
	// there is only one buffer, so no further management
	buffer = &device->dma_buffer;
	
	buffer->inuse = true;	
	
	RELEASE_BEN( &device->dma_buffer_lock );
	
	// memorize buffer for cleanup
	request->dma_buffer = buffer;
	
	// enlarge buffer if too small
	if( buffer->size < request->data_len ) {
		if( !scsi_alloc_dma_buffer( buffer, &device->bus->dma_params, 
			request->data_len ))
		{
			goto err;
		}
	}

	// create S/G to original data (necessary for copying from-buffer on end
	// of request, but also used during copying to-buffer in a second because
	// of lazyness)
	scsi_dma_buffer_compose_sg_orig( &device->dma_buffer, request );

	// copy data to buffer	
	if( (request->flags & SCSI_DIR_MASK) == SCSI_DIR_OUT ) {
		if( !scsi_copy_dma_buffer( request, request->data_len, true ))
			goto err;
	}
	
	// replace data address, so noone notices that a buffer is used
	buffer->orig_data = request->data;
	buffer->orig_sg_list = request->sg_list;
	buffer->orig_sg_cnt = request->sg_cnt;
	
	request->data = buffer->address;
	request->sg_list = buffer->sg_list;
	request->sg_cnt = buffer->sg_cnt;
	
	SHOW_INFO( 0, "bytes: %d", (int)request->data_len );

	SHOW_INFO0( 3, "we can start now" );
	
	request->buffered = true;
	return true;

err:
	SHOW_INFO0( 3, "error setting up DMA buffer" );
	
	ACQUIRE_BEN( &device->dma_buffer_lock );
	
	// some of this is probably not required, but I'm paranoid
	buffer->inuse = false;

	RELEASE_BEN( &device->dma_buffer_lock );
	release_sem( device->dma_buffer_owner );

	return false;	
}


// copy data back and release DMA buffer;
// you must have called cleanup_tmp_sg before
void scsi_release_dma_buffer( scsi_ccb *request )
{
	scsi_device_info *device = request->device;
	dma_buffer *buffer = request->dma_buffer;
	
	SHOW_FLOW( 0, "Buffering finished, %x, %x", 
		request->subsys_status & SCSI_SUBSYS_STATUS_MASK,
		(int)(request->flags & SCSI_DIR_MASK) );

	// copy data from buffer if required and if operation succeeded
	if( (request->subsys_status & SCSI_SUBSYS_STATUS_MASK) == SCSI_REQ_CMP &&
		(request->flags & SCSI_DIR_MASK) == SCSI_DIR_IN )
		scsi_copy_dma_buffer( request, request->data_len - request->data_resid, false );
		
	// restore request	
	request->data = buffer->orig_data;
	request->sg_list = buffer->orig_sg_list;
	request->sg_cnt = buffer->orig_sg_cnt;
	
	// free buffer
	ACQUIRE_BEN( &device->dma_buffer_lock );

	buffer->last_use = system_time();
	buffer->inuse = false;
	
	RELEASE_BEN( &device->dma_buffer_lock );
	
	release_sem( device->dma_buffer_owner );
	
	request->buffered = false;
}


// dameon that deletes DMA buffer if not used for some time
void scsi_dma_buffer_daemon( void *dev, int counter )
{
	scsi_device_info *device = dev;
	dma_buffer *buffer;

	ACQUIRE_BEN( &device->dma_buffer_lock );

	buffer = &device->dma_buffer;

	if( !buffer->inuse &&
		buffer->last_use - system_time() > SCSI_DMA_BUFFER_CLEANUP_DELAY ) 
	{
		scsi_free_dma_buffer( buffer );
		scsi_free_dma_buffer_sg_orig( buffer );		
	}
	
	RELEASE_BEN( &device->dma_buffer_lock );
}

void scsi_dma_buffer_free( dma_buffer *buffer )
{
	scsi_free_dma_buffer( buffer );
	scsi_free_dma_buffer_sg_orig( buffer );
}

void scsi_dma_buffer_init( dma_buffer *buffer )
{
	buffer->area = 0;
	buffer->size = 0;
	buffer->sg_orig = 0;
	buffer->sg_cnt_max_orig = 0;
}