linux-kernel - Re: [PATCH kernel v9 17/32] powerpc/powernv: Implement accessor to TCE entry

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Message-ID: <20150430001327.GZ32589@voom.redhat.com>
Date:	Thu, 30 Apr 2015 10:13:27 +1000
From:	David Gibson <david@...son.dropbear.id.au>
To:	Alexey Kardashevskiy <aik@...abs.ru>
Cc:	linuxppc-dev@...ts.ozlabs.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH kernel v9 17/32] powerpc/powernv: Implement accessor to
 TCE entry

On Wed, Apr 29, 2015 at 07:02:17PM +1000, Alexey Kardashevskiy wrote:
> On 04/29/2015 02:04 PM, David Gibson wrote:
> >On Sat, Apr 25, 2015 at 10:14:41PM +1000, Alexey Kardashevskiy wrote:
> >>This replaces direct accesses to TCE table with a helper which
> >>returns an TCE entry address. This does not make difference now but will
> >>when multi-level TCE tables get introduces.
> >>
> >>No change in behavior is expected.
> >>
> >>Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> >
> >Reviewed-by: David Gibson <david@...son.dropbear.id.au>
> >
> >
> >>---
> >>Changes:
> >>v9:
> >>* new patch in the series to separate this mechanical change from
> >>functional changes; this is not right before
> >>"powerpc/powernv: Implement multilevel TCE tables" but here in order
> >>to let the next patch - "powerpc/iommu/powernv: Release replaced TCE" -
> >>use pnv_tce() and avoid changing the same code twice
> >>---
> >>  arch/powerpc/platforms/powernv/pci.c | 34 +++++++++++++++++++++-------------
> >>  1 file changed, 21 insertions(+), 13 deletions(-)
> >>
> >>diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
> >>index 84b4ea4..ba75aa5 100644
> >>--- a/arch/powerpc/platforms/powernv/pci.c
> >>+++ b/arch/powerpc/platforms/powernv/pci.c
> >>@@ -572,38 +572,46 @@ struct pci_ops pnv_pci_ops = {
> >>  	.write = pnv_pci_write_config,
> >>  };
> >>
> >>+static __be64 *pnv_tce(struct iommu_table *tbl, long idx)
> >>+{
> >>+	__be64 *tmp = ((__be64 *)tbl->it_base);
> >>+
> >>+	return tmp + idx;
> >>+}
> >>+
> >>  int pnv_tce_build(struct iommu_table *tbl, long index, long npages,
> >>  		unsigned long uaddr, enum dma_data_direction direction,
> >>  		struct dma_attrs *attrs)
> >>  {
> >>  	u64 proto_tce = iommu_direction_to_tce_perm(direction);
> >>-	__be64 *tcep;
> >>-	u64 rpn;
> >>+	u64 rpn = __pa(uaddr) >> tbl->it_page_shift;
> >
> >I guess this was a problem in the existing code, not this patch.  But
> >"uaddr" is a really bad name (and unsigned long is a bad type) for
> >what must actually be a kernel linear mapping address.
> 
> 
> Yes and may be one day I'll clean this up. s/uaddr/linear/ and s/hwaddr/hpa/
> are the first things to do globally but not in this patchset.

Ok.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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