We've been having a discussion on the linuxppc-dev list about how to
handle IO memory that exists on some PPC SoC devices. These IO
memories behave like system memory but are faster to the processor or
device needed accessing for things like buffer descriptors.
Here's an example in which allocation is done either via system
memory or a specialized allocator for MURAM from drivers/net/ucc_geth.c:
(Yes, the system memory should be moved to use the dma mapping api)
if (uf_info->bd_mem_part == MEM_PART_SYSTEM) {
u32 align = 4;
if (UCC_GETH_TX_BD_RING_ALIGNMENT > 4)
align = UCC_GETH_TX_BD_RING_ALIGNMENT;
ugeth->tx_bd_ring_offset[j] =
kmalloc((u32) (length + align),
GFP_KERNEL);
if (ugeth->tx_bd_ring_offset[j] != 0)
ugeth->p_tx_bd_ring[j] =
(void*)((ugeth-
>tx_bd_ring_offset[j] +
align) & ~(align - 1));
} else if (uf_info->bd_mem_part == MEM_PART_MURAM) {
ugeth->tx_bd_ring_offset[j] =
qe_muram_alloc(length,
UCC_GETH_TX_BD_RING_ALIGNMENT);
if (!IS_MURAM_ERR(ugeth->tx_bd_ring_offset[j]))
ugeth->p_tx_bd_ring[j] =
(u8 *) qe_muram_addr(ugeth->
tx_bd_ring_offset[j]);
}
ideally all this would be handled via the dma mapping API, the
question is how to convey to the API to use the IO memory vs the
system memory? Should we look at adding a new GFP_IOMEM flag or do
something based on struct device?
Any ideas on direction (or if this is a solved problem elsewhere)
would be appreciated.
Thanks
- kumar
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
