Subject: Re: [RFC][PATCH 2/2] powerpc/fsl-pci Make PCIe hotplug work with Freescale

From: Rojhalat Ibrahim <[email-masked]>
Date: Mon, 18 Mar 2013 10:22:40 +0100

On Thursday 14 March 2013 15:35:40 Kumar Gala wrote:
> On Mar 14, 2013, at 4:43 AM, Rojhalat Ibrahim wrote:
> > On Wednesday 13 March 2013 14:07:16 Kumar Gala wrote:
> >> diff --git a/arch/powerpc/sysdev/fsl_pci.c
> >> b/arch/powerpc/sysdev/fsl_pci.c
> >> index 41bbcc4..b18c377 100644
> >> --- a/arch/powerpc/sysdev/fsl_pci.c
> >> +++ b/arch/powerpc/sysdev/fsl_pci.c
> >> @@ -74,6 +74,35 @@ static int __init fsl_pcie_check_link(struct
> >> pci_controller *hose) return 0;
> >> }
> >> 
> >> +static int fsl_indirect_read_config(struct pci_bus *bus, unsigned int
> >> devfn, +				    int offset, int len, u32 *val)
> >> +{
> >> +	struct pci_controller *hose = pci_bus_to_host(bus);
> >> +
> >> +	/* check the link status */
> >> +	if ((bus->number == hose->first_busno) && (devfn == 0)) {
> >> +		if (fsl_pcie_check_link(hose))
> >> +			hose->indirect_type |= PPC_INDIRECT_TYPE_NO_PCIE_LINK;
> >> +		else
> >> +			hose->indirect_type &= ~PPC_INDIRECT_TYPE_NO_PCIE_LINK;
> >> +	}
> >> +	return indirect_read_config(bus, devfn, offset, len, val);
> >> +}
> >> +
> > 
> > This does not work because fsl_indirect_read_config calls
> > fsl_pcie_check_link which calls early_read_config_dword which eventually
> > calls fsl_indirect_read_config, so the kernel hangs in a recursion loop.
> > Below is a modified patch that does work.
> ok, that makes sense, but I guess now its making me question the following statement:
> > if ((bus->number == hose->first_busno) && (devfn == 0)) {
> 
> Why do we have this conditional?
> 
> - k

Right. This is not necessary anymore. I modified the patch accordingly.

Signed-off-by: Rojhalat Ibrahim <[email-masked]>
---
 arch/powerpc/include/asm/pci-bridge.h |    6 ++++
 arch/powerpc/sysdev/fsl_pci.c         |   51 +++++++++++++++++++++++++++++-----
 arch/powerpc/sysdev/indirect_pci.c    |   10 ++----
 3 files changed, 54 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
index c0278f0..ffbc5fd 100644
--- a/arch/powerpc/include/asm/pci-bridge.h
+++ b/arch/powerpc/include/asm/pci-bridge.h
@@ -120,6 +120,12 @@ extern void setup_indirect_pci(struct pci_controller* hose,
 			       resource_size_t cfg_addr,
 			       resource_size_t cfg_data, u32 flags);
 
+extern int indirect_read_config(struct pci_bus *bus, unsigned int devfn,
+				int offset, int len, u32 *val);
+
+extern int indirect_write_config(struct pci_bus *bus, unsigned int devfn,
+				 int offset, int len, u32 val);
+
 static inline struct pci_controller *pci_bus_to_host(const struct pci_bus *bus)
 {
 	return bus->sysdata;
diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c
index 41bbcc4..9c0fcc9 100644
--- a/arch/powerpc/sysdev/fsl_pci.c
+++ b/arch/powerpc/sysdev/fsl_pci.c
@@ -54,12 +54,22 @@ static void quirk_fsl_pcie_header(struct pci_dev *dev)
 	return;
 }
 
-static int __init fsl_pcie_check_link(struct pci_controller *hose)
+static int fsl_indirect_read_config(struct pci_bus *, unsigned int,
+				    int, int, u32 *);
+
+static int fsl_pcie_check_link(struct pci_controller *hose)
 {
-	u32 val;
+	u32 val = 0;
 
 	if (hose->indirect_type & PPC_INDIRECT_TYPE_FSL_CFG_REG_LINK) {
-		early_read_config_dword(hose, 0, 0, PCIE_LTSSM, &val);
+		if (hose->ops->read == fsl_indirect_read_config) {
+			struct pci_bus bus;
+			bus.number = 0;
+			bus.sysdata = hose;
+			bus.ops = hose->ops;
+			indirect_read_config(&bus, 0, PCIE_LTSSM, 4, &val);
+		} else
+			early_read_config_dword(hose, 0, 0, PCIE_LTSSM, &val);
 		if (val < PCIE_LTSSM_L0)
 			return 1;
 	} else {
@@ -74,6 +84,33 @@ static int __init fsl_pcie_check_link(struct pci_controller *hose)
 	return 0;
 }
 
+static int fsl_indirect_read_config(struct pci_bus *bus, unsigned int devfn,
+				    int offset, int len, u32 *val)
+{
+	struct pci_controller *hose = pci_bus_to_host(bus);
+	
+	if (fsl_pcie_check_link(hose))
+		hose->indirect_type |= PPC_INDIRECT_TYPE_NO_PCIE_LINK;
+	else
+		hose->indirect_type &= ~PPC_INDIRECT_TYPE_NO_PCIE_LINK;
+	
+	return indirect_read_config(bus, devfn, offset, len, val);
+}
+
+static struct pci_ops fsl_indirect_pci_ops =
+{
+	.read = fsl_indirect_read_config,
+	.write = indirect_write_config,
+};
+
+static void __init fsl_setup_indirect_pci(struct pci_controller* hose,
+					  resource_size_t cfg_addr,
+					  resource_size_t cfg_data, u32 flags)
+{
+	setup_indirect_pci(hose, cfg_addr, cfg_data, flags);
+	hose->ops = &fsl_indirect_pci_ops;
+}
+
 #if defined(CONFIG_FSL_SOC_BOOKE) || defined(CONFIG_PPC_86xx)
 
 #define MAX_PHYS_ADDR_BITS	40
@@ -469,8 +506,8 @@ int __init fsl_add_bridge(struct platform_device *pdev, int is_primary)
 	if (!hose->private_data)
 		goto no_bridge;
 
-	setup_indirect_pci(hose, rsrc.start, rsrc.start + 0x4,
-		PPC_INDIRECT_TYPE_BIG_ENDIAN);
+	fsl_setup_indirect_pci(hose, rsrc.start, rsrc.start + 0x4,
+			       PPC_INDIRECT_TYPE_BIG_ENDIAN);
 
 	if (in_be32(&pci->block_rev1) < PCIE_IP_REV_3_0)
 		hose->indirect_type |= PPC_INDIRECT_TYPE_FSL_CFG_REG_LINK;
@@ -779,8 +816,8 @@ int __init mpc83xx_add_bridge(struct device_node *dev)
 		if (ret)
 			goto err0;
 	} else {
-		setup_indirect_pci(hose, rsrc_cfg.start,
-				   rsrc_cfg.start + 4, 0);
+		fsl_setup_indirect_pci(hose, rsrc_cfg.start,
+				       rsrc_cfg.start + 4, 0);
 	}
 
 	printk(KERN_INFO "Found FSL PCI host bridge at 0x%016llx. "
diff --git a/arch/powerpc/sysdev/indirect_pci.c b/arch/powerpc/sysdev/indirect_pci.c
index 82fdad8..c6c8b52 100644
--- a/arch/powerpc/sysdev/indirect_pci.c
+++ b/arch/powerpc/sysdev/indirect_pci.c
@@ -20,9 +20,8 @@
 #include <asm/pci-bridge.h>
 #include <asm/machdep.h>
 
-static int
-indirect_read_config(struct pci_bus *bus, unsigned int devfn, int offset,
-		     int len, u32 *val)
+int indirect_read_config(struct pci_bus *bus, unsigned int devfn,
+			 int offset, int len, u32 *val)
 {
 	struct pci_controller *hose = pci_bus_to_host(bus);
 	volatile void __iomem *cfg_data;
@@ -78,9 +77,8 @@ indirect_read_config(struct pci_bus *bus, unsigned int devfn, int offset,
 	return PCIBIOS_SUCCESSFUL;
 }
 
-static int
-indirect_write_config(struct pci_bus *bus, unsigned int devfn, int offset,
-		      int len, u32 val)
+int indirect_write_config(struct pci_bus *bus, unsigned int devfn,
+			  int offset, int len, u32 val)
 {
 	struct pci_controller *hose = pci_bus_to_host(bus);
 	volatile void __iomem *cfg_data;