DMA driver. Cache.
From: virgil (vanuichi_at_yahoo.com)
Date: 11/05/04
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Date: 5 Nov 2004 06:30:42 -0800
Hi all,
I'm having troubles with the following piece of code. It's a DMA
driver written in kernel, for MPC8245. Local to local memory.
The issue is: the values I see at the end of the transfer are the
uninitilized source values, instead of the initialized ones. It looks
like a cache problem. If it is I don't know how to invalidate the data
cache. Or, is it the type of memory I'm using?
Thanks,
Virgil
static int direct_dma_init(void)
{
U8* scr;
U32 tt;
int i;
sursa = kmalloc(64,GFP_KERNEL|GFP_DMA);
//sursa = __get_dma_pages(GFP_KERNEL,0);
dest = kmalloc(64,GFP_KERNEL|GFP_DMA);
printk("sursa:%x %x %x %x %x
%x\n",sursa[0],sursa[1],sursa[2],sursa[3],sursa,dest); // these are
the values I see at the end of dma transfer
dma_t = (volatile DMAS*) ioremap(DMA_SPACE(0),sizeof(DMAS));
dma_r = (volatile DMAS*) ioremap(DMA_SPACE(1),sizeof(DMAS));
for(i=0;i<8;i++)
{
sursa[i] = i+40;
}
printk("sursa:%x %x %x
%x\n",sursa[0],sursa[1],sursa[2],sursa[3]);//these should be the
values I see
printk("dma:%x %x %x %x\n",dma_t,dma_r,DMA_SPACE(0),DMA_SPACE(1));
if (readl(&dma_t->dsr) & 0x4) {
printk("nu pe aici0");
return;
}
writel(virt_to_bus(sursa),&dma_t->sar);//source address
writel(virt_to_bus(dest),&dma_t->dar);//destination address
writel(4,&dma_t->bcr);// 4 bytes to transfer
writel(0,&dma_t->cdar);
printk("prim %x %x %x %x %x %x\n",
(((U32)readl(&dma_t->dmr))),(((U32)readl(&dma_t->dsr))),
(((U32)readl(&dma_t->cdar))),(((U32)readl(&dma_t->sar))),
(((U32)readl(&dma_t->dar))),(((U32)readl(&dma_t->bcr))));
writel(4,&dma_t->dmr);
writel(5, &dma_t->dmr);// start dma
tt = readl(&dma_t->dsr);
writel(tt,&dma_t->dsr);
while(tt&0x4){ // just in case: wait to finish
tt = readl(&dma_t->dsr);
writel(tt,&dma_t->dsr);
}
printk("prim %x %x %x %x %x %x \n",
(((U32)readl(&dma_t->dmr))),(((U32)readl(&dma_t->dsr))),
(((U32)readl(&dma_t->cdar))),(((U32)readl(&dma_t->sar))),
(((U32)readl(&dma_t->dar))),(((U32)readl(&dma_t->bcr))));
printk("\ndest:%x %x %x %x",dest[0],dest[1],
dest[2],dest[3]);
}
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