Hello everybody,
it's my first post on the list, so be indulgent, I'm a newbee.
I'm writing a driver using a DMA transfer between on board RAM of a card and a memory ring buffer in kernel space. The processor is a Toshiba Tx49. The PCI controller is a PLX PCI9054 rev AC. It's seems to work fine.
The ring buffer in kernel space is then mmap()'ed in user's space using remap_page_range().
The kernel is a 2.4.22 - bigphys version.
The driver writes the pattern 0123456789 in this ring buffer (as uint32_t), and transfers those data on the on board ram thanks to the DMA (pci->local).
Then I transfer those data into the same ring buffer, but 10 uint32_t further. (local->pci)
So I may read 01234567890123456789.
I have to use a continuous memory ring buffer (about 2MBytes) due to the speed of the card.
That's why I allocated it firstly with bigphysarea patch. (I will describe it later)
As I encountered a problem with this patch, I tried to use pci_alloc_consistent (arch/mips/kernel/pci-dma.c) instead (after I read the O'Reilly Linux Driver book).
With this function, the DMA transfer succeeds (the pattern is ok: 01234567890123456789), but the mmap() call raised a PCI Bus error.
(I have seen in the mailing list that I probably have to modify mk_pte_phys(). Am I wrong?)
Now, my problem with bigphysarea.
The allocation of the ring buffer is done trough bigphysarea_alloc_pages (mm/bigphysarea.c). (I add bigphysarea=[number] as described in the documentation).
After boot, sometimes I read 01234567890000000000. Sometimes 01234567890000000089.
Then the next DMA transfer returns: 01234567890000006789
I tried to pass different flags to bigphysarea_alloc_pages (GFP_ATOMIC|GFP_DMA, GFP_KERNEL|GFP_DMA ...) without success.
I took a look at the source code of the two functions, and I tried to understand the difference, but the code is too dependent on the hardware for my knowledge))-;
pci_alloc_consistent and bigphysarea patch call finally __get_free_pages, but bigphysarea uses kmalloc call whereas pci_alloc_consistent makes some operation with dma_cache_wback_inv.
I know that the flag CONFIG_NONCOHERENT_IO is set.
The addresses of the ring buffer are respectively 0x27820000 and 0x002FA000 with bigphysarea and pci_alloc_consistent.
Are'nt bigphysarea and mips compliant?
How could I solve this problem?
Did anyone succeed with bigphysarea and mips in association?
Thanks a lot.
Regards,
/*this function allocated the ring buffer,with bigphysarea or pci_alloc_consistent
* bigphysarea is a global variable
*/
int alloc_ring_buffer(struct pci_dev *dev, uint32_t number_of_pages)
{
uint32_t free_mem=0;
PRIVDATA (dev)->PC_ring_buffer_size=number_of_pages*PAGE_SIZE;
if (bigphysarea){
printk("Using Bigphysarea\n");
bigphysarea_kinfo(&Free_Mem); /*returns the size of avialable memory*/
if (free_mem<number_of_pages*PAGE_SIZE)
printk("The bigphysarea reserved memory is too short\n");
else{
unsigned long size=PRIVDATA (dev)->PC_ring_buffer_size;
/*pci_alloc_consistent seems to use the flags : GFP_ATOMIC and GFP_DMA*/
PRIVDATA (dev)->PC_ring_buffer_virt_addr= (uint32_t* )
bigphysarea_alloc_pages (number_of_pages,1,/*GFP_ATOMIC|GFP_DMA*/GFP_KERNEL);
if (PRIVDATA (dev)->PC_ring_buffer_virt_addr) {
unsigned long adr = (unsigned long)PRIVDATA (dev)->PC_ring_buffer_virt_addr;
while (size > 0) {
mem_map_reserve(virt_to_page(phys_to_virt(adr)));
adr += PAGE_SIZE;
size -= PAGE_SIZE;
}
}
PRIVDATA (dev)->PC_ring_buffer_bus_addr=virt_to_bus (PRIVDATA (dev)->PC_ring_buffer_virt_addr);
}
}else{
printk("Using pci_alloc_consistent\n");
free_mem=free_mem;/*remove warning*/
/*allocation*/
PRIVDATA (dev)->PC_ring_buffer_virt_addr= pci_alloc_consistent(dev, PRIVDATA (dev)->PC_ring_buffer_size, &PRIVDATA (dev)->PC_ring_buffer_bus_addr);
/*put a flag to all the allocated pages*/
if (PRIVDATA (dev)->PC_ring_buffer_virt_addr){
struct page *page,*end_page;
/*the last page*/
end_page=virt_to_page(PRIVDATA (dev)->PC_ring_buffer_virt_addr+PRIVDATA (dev)->PC_ring_buffer_size-1);
for (page=virt_to_page(PRIVDATA (dev)->PC_ring_buffer_virt_addr);page<=end_page;page++)
set_bit(PG_reserved,&page->flags);
}
}
if (!(PRIVDATA (dev)->PC_ring_buffer_virt_addr)){
printk("Can't allocated contiguous memory\n");
return -ENOMEM;
}
else
printk("Allocation of the contiguous memory OK\nVirtual Address: %lX\n"\
"Bus physical Address: %lX\n",(unsigned long)PRIVDATA (dev)->PC_ring_buffer_virt_addr,(unsigned long)PRIVDATA (dev)->PC_ring_buffer_bus_addr);
memset(PRIVDATA (dev)->PC_ring_buffer_virt_addr,0,number_of_pages*PAGE_SIZE);
return 0;
}
/*-----------------------------------------------------------/
* pci_alloc_consistent
*
/*-----------------------------------------------------------*/
void *pci_alloc_consistent(struct pci_dev *hwdev, size_t size,
dma_addr_t * dma_handle)
{
void *ret;
int gfp = GFP_ATOMIC;
struct pci_bus *bus = NULL;
#ifdef CONFIG_ISA
if (hwdev == NULL || hwdev->dma_mask != 0xffffffff)
gfp |= GFP_DMA;
#endif
ret = (void *) __get_free_pages(gfp, get_order(size));
if (ret != NULL) {
memset(ret, 0, size);
if (hwdev)
bus = hwdev->bus;
*dma_handle = bus_to_baddr(bus, __pa(ret));
#ifdef CONFIG_NONCOHERENT_IO
dma_cache_wback_inv((unsigned long) ret, size);
ret = UNCAC_ADDR(ret);
#endif
}
return ret;
}
/*-----------------------------------------------------------/
* bigphysarea_alloc_pages
*
/*-----------------------------------------------------------*/
caddr_t bigphysarea_alloc_pages(int count, int align, int priority)
{
range_t *range, **range_ptr, *new_range, *align_range;
caddr_t aligned_base;
if (init_level < 2)
if (init2(priority))
return 0;
new_range = NULL;
align_range = NULL;
if (align == 0)
align = PAGE_SIZE;
else
align = align * PAGE_SIZE;
/*
* Search a free block which is large enough, even with alignment.
*/
range_ptr = &free_list;
while (*range_ptr != NULL) {
range = *range_ptr;
aligned_base =
(caddr_t)((((unsigned long)range->base + align - 1) / align) * align);
if (aligned_base + count * PAGE_SIZE <=
range->base + range->size)
break;
range_ptr = &range->next;
}
if (*range_ptr == NULL)
return 0;
range = *range_ptr;
/*
* When we have to align, the pages needed for alignment can
* be put back to the free pool.
* We check here if we need a second range data structure later
* and allocate it now, so that we don't have to check for a
* failed kmalloc later.
*/
if (aligned_base - range->base + count * PAGE_SIZE < range->size) {
new_range = kmalloc(sizeof(range_t), priority);
if (new_range == NULL)
return NULL;
}
if (aligned_base != range->base) {
align_range = kmalloc(sizeof(range_t), priority);
if (align_range == NULL) {
if (new_range != NULL)
kfree(new_range);
return NULL;
}
align_range->base = range->base;
align_range->size = aligned_base - range->base;
range->base = aligned_base;
range->size -= align_range->size;
align_range->next = range;
*range_ptr = align_range;
range_ptr = &align_range->next;
}
if (new_range != NULL) {
/*
* Range is larger than needed, create a new list element for
* the used list and shrink the element in the free list.
*/
new_range->base = range->base;
new_range->size = count * PAGE_SIZE;
range->base = new_range->base + new_range->size;
range->size = range->size - new_range->size;
} else {
/*
* Range fits perfectly, remove it from free list.
*/
*range_ptr = range->next;
new_range = range;
}
/*
* Insert block into used list
*/
new_range->next = used_list;
used_list = new_range;
return new_range->base;
}
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