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

-----Original Message-----
From: Kumar Gala [mailto:galak@kernel.crashing.org]
Sent: Thursday, February 08, 2007 1:58 PM
To: Li Yang-r58472
Cc: Tabi Timur-B04825; netdev@vger.kernel.org; linuxppc-dev@ozlabs.org
Subject: Re: [PATCH 1/4] ucc_geth: Change private immrbar_virt_to_phys

to generic

iopa


On Feb 7, 2007, at 11:52 PM, Li Yang-r58472 wrote:

quoted

quoted

-----Original Message-----
From: Timur Tabi [mailto:timur@freescale.com]
Sent: Thursday, February 08, 2007 1:03 AM
To: Kumar Gala
Cc: Li Yang-r58472; netdev@vger.kernel.org; linuxppc-dev@ozlabs.org
Subject: Re: [PATCH 1/4] ucc_geth: Change private
immrbar_virt_to_phys

to generic

quoted

iopa

Kumar Gala wrote:

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

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 >= (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
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 = virt_addr - PAGE_OFFSET.  While they can both be
mapped through page table using iopa().

- Leo