Re: [PATCH v1 3/9] parisc: Convert DMA map_page to map_phys interface

On 2025-10-03 1:26 p.m., Jason Gunthorpe wrote:

On Fri, Oct 03, 2025 at 01:18:32PM -0400, John David Anglin wrote:

quoted

On 2025-10-03 11:01 a.m., Jason Gunthorpe wrote:

quoted

This doesn't actually use the virt at all:

	offset = ((unsigned long) addr) & ~IOVP_MASK;
	if((size % L1_CACHE_BYTES) || ((unsigned long)addr % L1_CACHE_BYTES))
		ccio_io_pdir_entry(pdir_start, KERNEL_SPACE, (unsigned long)addr, hint);

And ccio_io_pdir_entry():
	pa = lpa(vba);

Is a special instruction that uses virt but AI tells me that special
LPA instruction is returning phys. Not sure if that is a different
value than virt_to_phys()..

ccio_io_pdir_entry currently only supports KERNEL_SPACE.  For KERNEL_SPACE, lpa() and
virt_to_phys() are equivalent if page is mapped.  lpa() returns 0 if a non-access data
TLB fault occurs (i.e., page isn't mapped).  Not sure if that
matters.

After unfolding everything the expression is

  lpa(phys_to_virt(pa))

So if that is always equal to pa then lets just drop it.

If lpa() was replaced by virt_to_phys(), the result would always be equal to pa.  So, I think it
can be dropped.

Dave
-- 
John David Anglin  dave.anglin@bell.net