linux-kernel - Re: [PATCH kernel v10 22/34] powerpc/powernv: Implement accessor to TCE entry

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Date:	Thu, 14 May 2015 12:34:00 +1000
From:	Gavin Shan <gwshan@...ux.vnet.ibm.com>
To:	Alexey Kardashevskiy <aik@...abs.ru>
Cc:	linuxppc-dev@...ts.ozlabs.org,
	David Gibson <david@...son.dropbear.id.au>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH kernel v10 22/34] powerpc/powernv: Implement accessor to
 TCE entry

On Tue, May 12, 2015 at 01:39:11AM +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>

Reviewed-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>

Thanks,
Gavin

>---
>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 ed7de7b..cc82f05 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;
>+	long i;
>
>-	tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
>-	rpn = __pa(uaddr) >> tbl->it_page_shift;
>-
>-	while (npages--)
>-		*(tcep++) = cpu_to_be64(proto_tce |
>-				(rpn++ << tbl->it_page_shift));
>+	for (i = 0; i < npages; i++) {
>+		unsigned long newtce = proto_tce |
>+			((rpn + i) << tbl->it_page_shift);
>+		unsigned long idx = index - tbl->it_offset + i;
>
>+		*(pnv_tce(tbl, idx)) = cpu_to_be64(newtce);
>+	}
>
> 	return 0;
> }
>
> void pnv_tce_free(struct iommu_table *tbl, long index, long npages)
> {
>-	__be64 *tcep;
>+	long i;
>
>-	tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
>+	for (i = 0; i < npages; i++) {
>+		unsigned long idx = index - tbl->it_offset + i;
>
>-	while (npages--)
>-		*(tcep++) = cpu_to_be64(0);
>+		*(pnv_tce(tbl, idx)) = cpu_to_be64(0);
>+	}
> }
>
> unsigned long pnv_tce_get(struct iommu_table *tbl, long index)
> {
>-	return ((u64 *)tbl->it_base)[index - tbl->it_offset];
>+	return *(pnv_tce(tbl, index - tbl->it_offset));
> }
>
> struct iommu_table *pnv_pci_table_alloc(int nid)
>-- 
>2.4.0.rc3.8.gfb3e7d5
>

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