netdev - RE: [PATCH 1/4] ucc_geth: Change private immrbar_virt_to

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Date:	Thu, 8 Feb 2007 14:48:04 +0800
From:	"Li Yang-r58472" <LeoLi@...escale.com>
To:	"Kumar Gala" <galak@...nel.crashing.org>
Cc:	"Tabi Timur-B04825" <timur@...escale.com>,
	<netdev@...r.kernel.org>, <linuxppc-dev@...abs.org>
Subject: RE: [PATCH 1/4] ucc_geth: Change private immrbar_virt_to_phys to generic iopa

> -----Original Message-----
> From: Kumar Gala [mailto:galak@...nel.crashing.org]
> Sent: Thursday, February 08, 2007 1:58 PM
> To: Li Yang-r58472
> Cc: Tabi Timur-B04825; netdev@...r.kernel.org; linuxppc-dev@...abs.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:
> 
> >> -----Original Message-----
> >> From: Timur Tabi [mailto:timur@...escale.com]
> >> Sent: Thursday, February 08, 2007 1:03 AM
> >> To: Kumar Gala
> >> Cc: Li Yang-r58472; netdev@...r.kernel.org; linuxppc-dev@...abs.org
> >> Subject: Re: [PATCH 1/4] ucc_geth: Change private
> >> immrbar_virt_to_phys
> > to generic
> >> iopa
> >>
> >> Kumar Gala wrote:
> >>
> >>> If its been mapped with ioremap() you know the physical address
> > already
> >>> so why do you need iopa().
> >>
> >> That's what the original function immrbar_virt_to_phys() does.
We're
> > trying to
> >> get rid of it, because we thought is redundant with iopa().
> >>
> >> static inline unsigned long immrbar_virt_to_phys(volatile void *
> > address)
> >> {
> >> 	if ( ((u32)address >= (u32)qe_immr) &&
> >> 			((u32)address < ((u32)qe_immr + QE_IMMAP_SIZE))
> > )
> >> 		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
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