[PATCH v2] powerpc/powernv/pci: Drop pnv_phb->initialized

[PATCH v2] powerpc/powernv/pci: Drop pnv_phb->initialized

[Oliver O'Halloran]

The pnv_phb->initialized flag is an odd beast. It was added back in 2012 in
commit db1266c85261 ("powerpc/powernv: Skip check on PE if necessary") to
allow devices to be enabled even if the device had not yet been assigned to
a PE. Allowing the device to be enabled before the PE is configured may
cause spurious EEH events since none of the IOMMU context has been setup.

I'm not entirely sure why this was ever necessary. My best guess is that it
was an workaround for a bug or some other undesireable behaviour from the
PCI core. Either way, it's unnecessary now since as of commit dc3d8f85bb57
("powerpc/powernv/pci: Re-work bus PE configuration") we can guarantee that
the PE will be configured before the PCI core will allow drivers to bind to
the device.

It's also worth pointing out that the ->initialized flag is only set in
pnv_pci_ioda_create_dbgfs(). That function has its entire body wrapped
in #ifdef CONFIG_DEBUG_FS. As a result, for kernels built without debugfs
(i.e. petitboot) the other checks in pnv_pci_enable_device_hook() are
bypassed entirely.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
---
v2: reword commit message a bit
---
 arch/powerpc/platforms/powernv/pci-ioda.c | 17 -----------------
 arch/powerpc/platforms/powernv/pci.h      |  1 -
 2 files changed, 18 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 023a4f987bb2..6ac3c637b313 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -2410,9 +2410,6 @@ static void pnv_pci_ioda_create_dbgfs(void)
 	list_for_each_entry_safe(hose, tmp, &hose_list, list_node) {
 		phb = hose->private_data;
 
-		/* Notify initialization of PHB done */
-		phb->initialized = 1;
-
 		sprintf(name, "PCI%04x", hose->global_number);
 		phb->dbgfs = debugfs_create_dir(name, powerpc_debugfs_root);
 
@@ -2609,17 +2606,8 @@ static resource_size_t pnv_pci_default_alignment(void)
  */
 static bool pnv_pci_enable_device_hook(struct pci_dev *dev)
 {
-	struct pnv_phb *phb = pci_bus_to_pnvhb(dev->bus);
 	struct pci_dn *pdn;
 
-	/* The function is probably called while the PEs have
-	 * not be created yet. For example, resource reassignment
-	 * during PCI probe period. We just skip the check if
-	 * PEs isn't ready.
-	 */
-	if (!phb->initialized)
-		return true;
-
 	pdn = pci_get_pdn(dev);
 	if (!pdn || pdn->pe_number == IODA_INVALID_PE)
 		return false;
@@ -2629,14 +2617,9 @@ static bool pnv_pci_enable_device_hook(struct pci_dev *dev)
 
 static bool pnv_ocapi_enable_device_hook(struct pci_dev *dev)
 {
-	struct pci_controller *hose = pci_bus_to_host(dev->bus);
-	struct pnv_phb *phb = hose->private_data;
 	struct pci_dn *pdn;
 	struct pnv_ioda_pe *pe;
 
-	if (!phb->initialized)
-		return true;
-
 	pdn = pci_get_pdn(dev);
 	if (!pdn)
 		return false;
diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
index 739a0b3b72e1..36d22920f5a3 100644
--- a/arch/powerpc/platforms/powernv/pci.h
+++ b/arch/powerpc/platforms/powernv/pci.h
@@ -119,7 +119,6 @@ struct pnv_phb {
 	int			flags;
 	void __iomem		*regs;
 	u64			regs_phys;
-	int			initialized;
 	spinlock_t		lock;
 
 #ifdef CONFIG_DEBUG_FS
-- 
2.26.2

Re: [PATCH v2] powerpc/powernv/pci: Drop pnv_phb->initialized

[Michael Ellerman]

On Wed, 2 Sep 2020 11:36:57 +1000, Oliver O'Halloran wrote:
> The pnv_phb->initialized flag is an odd beast. It was added back in 2012 in
> commit db1266c85261 ("powerpc/powernv: Skip check on PE if necessary") to
> allow devices to be enabled even if the device had not yet been assigned to
> a PE. Allowing the device to be enabled before the PE is configured may
> cause spurious EEH events since none of the IOMMU context has been setup.
> 
> I'm not entirely sure why this was ever necessary. My best guess is that it
> was an workaround for a bug or some other undesireable behaviour from the
> PCI core. Either way, it's unnecessary now since as of commit dc3d8f85bb57
> ("powerpc/powernv/pci: Re-work bus PE configuration") we can guarantee that
> the PE will be configured before the PCI core will allow drivers to bind to
> the device.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/powernv/pci: Drop pnv_phb->initialized
      https://git.kernel.org/powerpc/c/24b4c6b1a7fc79fe8142d50cb439944b81b659ff

cheers