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

From: Alexey Kardashevskiy <[email-masked]>
Date: Thu, 6 Aug 2015 19:00:00 +1000

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)?

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?

>
>> 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