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

David Gibson
2015-04-29T05:50:06Z

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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@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.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.

> + 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));
> }
>
> void pnv_pci_setup_iommu_table(struct iommu_table *tbl,

--
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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