RE: [PATCH 1/4] ucc_geth: Change private immrbar_virt_to_phys to generic iopa

quoted

quoted

quoted

quoted

quoted

If its been mapped with ioremap() you know the physical address

already

quoted

quoted

so why do you need iopa().

That's what the original function immrbar_virt_to_phys() does.

We're

quoted

quoted

trying to

quoted

get rid of it, because we thought is redundant with iopa().

static inline unsigned long immrbar_virt_to_phys(volatile void *

address)

quoted

{
	if ( ((u32)address >=3D (u32)qe_immr) &&
			((u32)address < ((u32)qe_immr + QE_IMMAP_SIZE))

)

quoted

		return (unsigned long)(address - (u32)qe_immr +
				(u32)get_qe_base());
	return (unsigned long)virt_to_phys(address);
}

get_qe_base() does a search of the OF tree the first time it's
called.

Here's the code that calls immrbar_virt_to_phys():

	out_be32(&ugeth->p_send_q_mem_reg->sqqd[i].bd_ring_base,
		 (u32) immrbar_virt_to_phys(ugeth->
					    p_tx_bd_ring[i]));


Would it be better to replace this code with something like this:

out_be32(&ugeth->p_send_q_mem_reg->sqqd[i].bd_ring_base,
	get_qe_base() + ((void *) ugeth->p_tx_bd_ring[i] - (void *)

qe_immr));

No, we don't know if the BD ring is in MURAM or main memory as it

is

quoted

quoted

quoted

configurable.  iopa() is best choice to handle both case, IMHO.

Does MURAM behave differently than normal memory?

MURAM is a mmio region so it don't share the characteristic of main
memory that phy_addr =3D virt_addr - PAGE_OFFSET.  While they can
both be
mapped through page table using iopa().

=20
Right, so when do you know if you'll be using MURAM or normal
memory?  Why not just keep around a token that is the physical
address at the point you make the decision of MURAM vs normal memory.

Yes, that can be a way.  But as the virt to phy mapping is only used
once, it's nothing bad to do it this way.

- Leo