Subject: Re: [PATCH V3 8/9] powerpc/powernv: Support PCI config restore for VFs

From: Wei Yang <[email-masked]>
Date: Tue, 12 May 2015 09:31:34 +0800

On Mon, May 11, 2015 at 02:22:38PM +1000, Gavin Shan wrote:
>On Mon, May 04, 2015 at 03:07:37PM +0800, Wei Yang wrote:
>>Since FW is not aware of VFs, the restore action for VF should be done in
>       ^^
>       skiboot firmware
>>kernel.
>>
>>This patch introduces pnv_eeh_vf_restore_config() for VF.
>>
>
>Would it be better?
>
>The patch introduces function pnv_eeh_vf_restore_config() to restore PCI
>config space for VFs after reset.
>

Ok.

>Also, the function name would be better with pnv_eeh_restore_vf_config()?

Ok.

>
>>Signed-off-by: Wei Yang <[email-masked]>
>>---
>> arch/powerpc/include/asm/pci-bridge.h        |    1 +
>> arch/powerpc/platforms/powernv/eeh-powernv.c |   77 +++++++++++++++++++++++++-
>> 2 files changed, 77 insertions(+), 1 deletion(-)
>>
>>diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
>>index 9582aa2..de55ef6 100644
>>--- a/arch/powerpc/include/asm/pci-bridge.h
>>+++ b/arch/powerpc/include/asm/pci-bridge.h
>>@@ -205,6 +205,7 @@ struct pci_dn {
>> 	int     m64_per_iov;
>> #define IODA_INVALID_M64        (-1)
>> 	int     m64_wins[PCI_SRIOV_NUM_BARS][M64_PER_IOV];
>>+	int	mps;
>> #endif /* CONFIG_PCI_IOV */
>> #endif
>> 	struct list_head child_list;
>>diff --git a/arch/powerpc/platforms/powernv/eeh-powernv.c b/arch/powerpc/platforms/powernv/eeh-powernv.c
>>index 1ad322f..6ba6d87 100644
>>--- a/arch/powerpc/platforms/powernv/eeh-powernv.c
>>+++ b/arch/powerpc/platforms/powernv/eeh-powernv.c
>>@@ -1589,6 +1589,59 @@ static int pnv_eeh_next_error(struct eeh_pe **pe)
>> 	return ret;
>> }
>>
>>+#ifdef CONFIG_PCI_IOV
>>+static int pnv_eeh_vf_restore_config(struct pci_dn *pdn)
>>+{
>>+	int pcie_cap, aer_cap, old_mps;
>>+	u32 devctl, cmd, cap2, aer_capctl;
>>+
>>+	/* Restore MPS */
>>+	pcie_cap = pnv_eeh_find_cap(pdn, PCI_CAP_ID_EXP);
>>+	if (pcie_cap) {
>>+		old_mps = (ffs(pdn->mps) - 8) << 5;
>>+		pnv_pci_cfg_read(pdn, pcie_cap + PCI_EXP_DEVCTL, 2, &devctl);
>>+		devctl &= ~PCI_EXP_DEVCTL_PAYLOAD;
>>+		devctl |= old_mps;
>>+		pnv_pci_cfg_write(pdn, pcie_cap + PCI_EXP_DEVCTL, 2, devctl);
>>+	}
>>+
>
>hrm, You can't use pnv_pci_cfg_{read,write} here. Instead, you should use
>eeh_ops->{read,write}_config. By design, the PCI config accessors have been
>classified to 2 classes: one is used for pci_config_{read,write}_* and another
>one is eeh_ops->{read,write}. From EEH perspective, the former isn't controlled
>strictly, but the later one is under control completely. "Not controlled" here
>means the kernel can't determine when the PCI config is accessed, e.g. PCI
>config accesses from user land.
>

Reasonable, will change it.

>>+	/* Disable Completion Timeout */
>>+	if (pcie_cap) {
>>+		pnv_pci_cfg_read(pdn, pcie_cap + PCI_EXP_DEVCAP2, 4, &cap2);
>>+		if (cap2 & 0x10) {
>>+			pnv_pci_cfg_read(pdn, pcie_cap + PCI_EXP_DEVCTL2, 4, &cap2);
>>+			cap2 |= 0x10;
>>+			pnv_pci_cfg_write(pdn, pcie_cap + PCI_EXP_DEVCTL2, 4, cap2);
>>+		}
>>+	}
>>+
>>+	/* Enable SERR and parity checking */
>>+	pnv_pci_cfg_read(pdn, PCI_COMMAND, 2, &cmd);
>>+	cmd |= (PCI_COMMAND_PARITY | PCI_COMMAND_SERR);
>>+	pnv_pci_cfg_write(pdn, PCI_COMMAND, 2, cmd);
>>+
>>+	/* Enable report various errors */
>>+	if (pcie_cap) {
>>+		pnv_pci_cfg_read(pdn, pcie_cap + PCI_EXP_DEVCTL, 2, &devctl);
>>+		devctl &= ~PCI_EXP_DEVCTL_CERE;
>>+		devctl |= (PCI_EXP_DEVCTL_NFERE |
>>+			   PCI_EXP_DEVCTL_FERE |
>>+			   PCI_EXP_DEVCTL_URRE);
>>+		pnv_pci_cfg_write(pdn, pcie_cap + PCI_EXP_DEVCTL, 2, devctl);
>>+	}
>>+
>>+	/* Enable ECRC generation and check */
>>+	if (pcie_cap) {
>>+		aer_cap = pnv_eeh_find_ecap(pdn, PCI_EXT_CAP_ID_ERR);
>>+		pnv_pci_cfg_read(pdn, aer_cap + PCI_ERR_CAP, 4, &aer_capctl);
>>+		aer_capctl |= (PCI_ERR_CAP_ECRC_GENE | PCI_ERR_CAP_ECRC_CHKE);
>>+		pnv_pci_cfg_write(pdn, aer_cap + PCI_ERR_CAP, 4, aer_capctl);
>>+	}
>>+
>>+	return 0;
>>+}
>>+#endif /* CONFIG_PCI_IOV */
>>+
>
>The code is copied over from skiboot firmware. I still dislike the fact that
>we have to maintain two sets of similar functions in skiboot/kernel. I still
>believe the way I suggested can help: the firmware exports the error routing
>rules and kernel has support it based on the rules. With it, the skiboot is
>the source of the information to avoid mismatching between kernel/firmware.

Yes, it looks we have duplicate code in kernel and skiboot.

As you suggest, if we export some bit map from device node, we still have the
real logic in kernel, until we remove that part in skiboot.

By removing that part in skiboot, we may have some compatibility problem. For
example, an old kernel may not run on the new version of skiboot.

>
>> static int pnv_eeh_restore_config(struct pci_dn *pdn)
>> {
>> 	struct eeh_dev *edev = pdn_to_eeh_dev(pdn);
>>@@ -1599,7 +1652,13 @@ static int pnv_eeh_restore_config(struct pci_dn *pdn)
>> 		return -EEXIST;
>>
>> 	phb = edev->phb->private_data;
>>-	ret = opal_pci_reinit(phb->opal_id,
>>+#ifdef CONFIG_PCI_IOV
>>+	/* FW is not VF aware, we rely on OS to restore it */
>>+	if (edev->mode & EEH_DEV_VF)
>>+		ret = pnv_eeh_vf_restore_config(pdn);
>>+	else
>>+#endif
>
>You don't even have to have CONFIG_PCI_IOV since it won't save much
>.text space.
>

ok

>>+		ret = opal_pci_reinit(phb->opal_id,
>> 			      OPAL_REINIT_PCI_DEV, edev->config_addr);
>> 	if (ret) {
>> 		pr_warn("%s: Can't reinit PCI dev 0x%x (%lld)\n",
>>@@ -1660,4 +1719,20 @@ static void pnv_pci_fixup_vf_eeh(struct pci_dev *pdev)
>> 	}
>> }
>> DECLARE_PCI_FIXUP_FINAL(PCI_ANY_ID, PCI_ANY_ID, pnv_pci_fixup_vf_eeh);
>>+
>>+static void pnv_pci_fixup_vf_caps(struct pci_dev *pdev)
>>+{
>
>As I said before, this function shouldn't be part of this file because:
>
>- When CONFIG_EEH=n, this file won't be complied/included.
>- This function isn't part of EEH naturally.
>

Moved to arch/powerpc/platform/powernv/pci.c

>Also, pnv_pci_vf_header_fixup() would be better name in case you need
>apply more fixups for VFs in the function.
>

Ok.

>>+	struct pci_dn *pdn = pci_get_pdn(pdev);
>>+	int parent_mps;
>>+
>>+	if (!pdev->is_virtfn)
>>+		return;
>>+
>>+	/* Synchronize MPS for VF and PF */
>>+	parent_mps = pcie_get_mps(pdev->physfn);
>>+	if ((128 << pdev->pcie_mpss) >= parent_mps)
>>+		pcie_set_mps(pdev, parent_mps);
>
>Hrm, Again, do we have possibility: (128 << pdev->pcie_mpss) < parent_mps ?
>And why we bother if MPS of PF/VF are equal?
>

pcie_mpss is the MPS supported, not the MPS itself.

This line means if the pci_dev support the parents mps, apply it.
Otherwise, just cache the mps.

>>+	pdn->mps = pcie_get_mps(pdev);
>>+}
>>+DECLARE_PCI_FIXUP_HEADER(PCI_ANY_ID, PCI_ANY_ID, pnv_pci_fixup_vf_caps);
>> #endif /* CONFIG_PCI_IOV */
>>-- 
>>1.7.9.5
>>
>
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-- 
Richard Yang
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