Re: [PATCH V5 2/6] powerpc/powernv: simplify the calculation of iov resource alignment

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

On Tue, Oct 13, 2015 at 10:45:45AM +0800, Wei Yang wrote:
>On Tue, Oct 13, 2015 at 11:13:50AM +1100, Gavin Shan wrote:
>>On Fri, Oct 09, 2015 at 10:46:52AM +0800, Wei Yang wrote:
>>>The alignment of IOV BAR on PowerNV platform is the total size of the IOV
>>>BAR. No matter whether the IOV BAR is extended with number of
>>>roundup_pow_of_two(total_vfs) or number of max PE number (256), the total
>>>size could be calculated by (vfs_expanded * VF_BAR_size).
>>>
>>>This patch simplifies the pnv_pci_iov_resource_alignment() by removing the
>>>first case.
>>>
>>>Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
>>>Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>>>Acked-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>---
>>> arch/powerpc/platforms/powernv/pci-ioda.c | 20 ++++++++++++--------
>>> 1 file changed, 12 insertions(+), 8 deletions(-)
>>>
>>>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>>>index 8c031b5..7da476b 100644
>>>--- a/arch/powerpc/platforms/powernv/pci-ioda.c
>>>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>>>@@ -2988,17 +2988,21 @@ static resource_size_t pnv_pci_iov_resource_alignment(struct pci_dev *pdev,
>>> 						      int resno)
>>> {
>>> 	struct pci_dn *pdn = pci_get_pdn(pdev);
>>>-	resource_size_t align, iov_align;
>>>-
>>>-	iov_align = resource_size(&pdev->resource[resno]);
>>>-	if (iov_align)
>>>-		return iov_align;
>>>+	resource_size_t align;
>>>
>>>+	/*
>>>+	 * On PowerNV platform, IOV BAR is mapped by M64 BAR to enable the
>>>+	 * SR-IOV. While from hardware perspective, the range mapped by M64
>>>+	 * BAR should be size aligned.
>>>+	 *
>>>+	 * This function returns the total IOV BAR size if M64 BAR is in
>>>+	 * Shared PE mode or just the individual size if not.
>>>+	 */
>>
>>s/the invidial size/VF BAR size
>>
>>> 	align = pci_iov_resource_size(pdev, resno);
>>>-	if (pdn->vfs_expanded)
>>>-		return pdn->vfs_expanded * align;
>>>+	if (!pdn->vfs_expanded)
>>>+		return align;
>>>
>>>-	return align;
>>>+	return pdn->vfs_expanded * align;
>>
>>There is no difference before/after the changes. why this change is needed?
>>
>
>After change the logic is more clear.
>
>Alignment equals to the total size when IOV BAR is expanded or equals to the
>VF BAR size. We don't need to check whether IOV BAR is truncated.
>

I didn't get what you're talking about with "IOV BAR is truncated". I also
didn't get what has been really changed from last 3 lines changes.

	if (pdn->vfs_expanded)				if (!pdn->vfs_expanded)
		return pdn->vfs_expanded * align;		return align;
	return align;					return pdn->vfs_expanded * align;

>>> }
>>> #endif /* CONFIG_PCI_IOV */
>>>
>>>-- 
>>>2.5.0
>>>
>
>-- 
>Richard Yang
>Help you, Help me