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

Alexey Kardashevskiy
2015-04-29T09:02:28Z

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@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.

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.

>
>> + 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,
>

--
Alexey