Subject: Re: [PATCH v3 4/6] powerpc/powernv: replace the hard coded boundary with gate

From: Gavin Shan <[email-masked]>
Date: Fri, 14 Aug 2015 10:54:02 +1000

On Thu, Aug 13, 2015 at 10:11:09PM +0800, Wei Yang wrote:
>At the moment 64bit-prefetchable window can be maximum 64GB, which is
>currently got from device tree. This means that in shared mode the maximum
>supported VF BAR size is 64GB/256=256MB. While this size could exhaust the
>whole 64bit-prefetchable window. This is a design decision to set a
>boundary to 64MB of the VF BAR size. Since VF BAR size with 64MB would
>occupy a quarter of the 64bit-prefetchable window, this is affordable.
>
>This patch replaces magic limit of 64MB with (m64_segsize >> 1) and adds
>comment to explain the reason for it.
>
>Signed-off-by: Wei Yang <[email-masked]>

Reviewed-by: Gavin Shan <[email-masked]>

>---
> arch/powerpc/platforms/powernv/pci-ioda.c |   22 +++++++++++++++++-----
> 1 file changed, 17 insertions(+), 5 deletions(-)
>
>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>index 4da0f50..3e8c0b4 100644
>--- a/arch/powerpc/platforms/powernv/pci-ioda.c
>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>@@ -2688,7 +2688,7 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
> 	struct pnv_phb *phb;
> 	struct resource *res;
> 	int i;
>-	resource_size_t size;
>+	resource_size_t size, gate;
> 	struct pci_dn *pdn;
> 	int mul, total_vfs;
>
>@@ -2704,6 +2704,17 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>
> 	total_vfs = pci_sriov_get_totalvfs(pdev);
> 	mul = phb->ioda.total_pe;
>+	/*
>+	 * If bigger than or equal to half of M64 segment size, just round up
>+	 * power of two.
>+	 *
>+	 * Generally, one M64 BAR maps one IOV BAR. To avoid conflict with
>+	 * other devices, IOV BAR size is expanded to be (total_pe *
>+	 * VF_BAR_size).  When VF_BAR_size is half of M64 segment size , the
>+	 * expanded size would equal to half of the whole M64 Space size,
>+	 * which will exhaust the M64 Space and limit the system flexibility.
>+	 */

s/M64 Space/M64 space

>+	gate = phb->ioda.m64_segsize >> 1;
>
> 	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
> 		res = &pdev->resource[i + PCI_IOV_RESOURCES];
>@@ -2718,10 +2729,11 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>
> 		size = pci_iov_resource_size(pdev, i + PCI_IOV_RESOURCES);
>
>-		/* bigger than 64M */
>-		if (size > (1 << 26)) {
>-			dev_info(&pdev->dev, "PowerNV: VF BAR%d: %pR IOV size is bigger than 64M, roundup power2\n",
>-				 i, res);
>+		/* bigger than or equal to gate */
>+		if (size >= gate) {
>+			dev_info(&pdev->dev, "PowerNV: VF BAR%d: %pR IOV size "
>+				"is bigger than %lld, roundup power2\n",
>+				 i, res, gate);
> 			mul = roundup_pow_of_two(total_vfs);
> 			pdn->m64_single_mode = true;
> 			break;
>-- 
>1.7.9.5
>