Subject: Re: [PATCH V2 2/6] powerpc/powernv: simplify the calculation of iov resource

From: Wei Yang <[email-masked]>
Date: Thu, 6 Aug 2015 17:41:02 +0800

On Thu, Aug 06, 2015 at 07:00:00PM +1000, Alexey Kardashevskiy wrote:
>On 08/06/2015 02:51 PM, Gavin Shan wrote:
>>On Wed, Aug 05, 2015 at 09:24:59AM +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 truncated or not, the total size
>>>could be calculated by (vfs_expanded * VF size).
>>>
>>
>>s/VF size/VF BAR size
>>
>>I think the changelog would be more explicit:
>>
>>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 max
>>VFs or number of max PE number (256). The alignment can be calculated
>>by (vfs_expaned * VF_BAR_size).
>
>
>
>Is that really a PowerNV-specific requirement or it is valid for
>every platform (I suspect this is the case here)?
>

Currently, it is PowerNV-specific.

>
>Also, what is the exact meaning of "expanded" in @vfs_expanded? It is
>either 255 (if individual VF BARs are <= 64MB) or
>roundup_pow_of_two(total_vfs) (which is something like 4 or 16). What
>is expanded here?
>

PF's IOV BAR original size is (VF BAR size * total_vfs). 

After expanding, the IOV BAR size  is (VF BAR size * 256) or (VF BAR size *
roundup_pow_of_two(total_vfs)).

>
>>
>>>This patch simplifies the pnv_pci_iov_resource_alignment() by removing the
>>>first case.
>>>
>>>Signed-off-by: Wei Yang <[email-masked]>
>>
>>Reviewed-by: Gavin Shan <[email-masked]>
>>
>>>---
>>>arch/powerpc/platforms/powernv/pci-ioda.c |   14 +++++++++-----
>>>1 file changed, 9 insertions(+), 5 deletions(-)
>>>
>>>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>>>index 9b41dba..7192e62 100644
>>>--- a/arch/powerpc/platforms/powernv/pci-ioda.c
>>>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>>>@@ -2987,12 +2987,16 @@ 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 return the total IOV BAR size if expanded or just the
>>>+	 * individual size if not.
>>>+	 */
>>>	align = pci_iov_resource_size(pdev, resno);
>>>	if (pdn->vfs_expanded)
>>>		return pdn->vfs_expanded * align;
>>>--
>>>1.7.9.5
>>>
>>
>
>
>-- 
>Alexey

-- 
Richard Yang
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