Patchwork [PATCHv2,3/3] ppc64: implemented pcibios_get_speed_cap_mask

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Submitter Lucas Kannebley Tavares
Date March 20, 2013, 5:24 a.m.
Message ID <1363757079-23550-4-git-send-email-lucaskt@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/229249/
State Changes Requested
Headers show

Comments

Lucas Kannebley Tavares - March 20, 2013, 5:24 a.m.
Implementation of a architecture-specific pcibios_get_speed_cap_mask.
This implementation detects bus capabilities based on OF
ibm,pcie-link-speed-stats property.

Signed-off-by: Lucas Kannebley Tavares <lucaskt@linux.vnet.ibm.com>
---
 arch/powerpc/platforms/pseries/pci.c |   35 ++++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+), 0 deletions(-)
Benjamin Herrenschmidt - March 20, 2013, 5:39 a.m.
On Wed, 2013-03-20 at 02:24 -0300, Lucas Kannebley Tavares wrote:
> Implementation of a architecture-specific pcibios_get_speed_cap_mask.
> This implementation detects bus capabilities based on OF
> ibm,pcie-link-speed-stats property.

The problem with your approach is that it's not a runtime detection...

If the pseries machine is compiled into the kernel binary, it will
override pcibios_get_speed_cap_mask() using the device-tree, regardless
of whether the machine is currently booted on a pseries machine or not.

This wouldn't be a big problem if the pseries
pcibios_get_speed_cap_mask() was capable of doing a fallback to the
generic one if the device-tree property is absent but that isn't the
case.

I think what you need to do is:

  - Make it so the generic one can be called by the override. This can
look a bit tricky but it's better that way. One way to do it is to have
the actual implementation be in a __pci_* variant called by the weak
pcibios_* variant

  - Move the powerpc on to arch/powerpc/kernel/pci-common.c and make
it call a ppc_md.pcibios_get_speed_cap_mask(). If the hook is absent
(NULL), make it call the generic one

  - pseries can then populate the hook in ppc_md. with its custom
variant.

Cheers,
Ben.


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Patch

diff --git a/arch/powerpc/platforms/pseries/pci.c b/arch/powerpc/platforms/pseries/pci.c
index 0b580f4..4da8deb 100644
--- a/arch/powerpc/platforms/pseries/pci.c
+++ b/arch/powerpc/platforms/pseries/pci.c
@@ -24,6 +24,7 @@ 
 #include <linux/kernel.h>
 #include <linux/pci.h>
 #include <linux/string.h>
+#include <linux/device.h>
 
 #include <asm/eeh.h>
 #include <asm/pci-bridge.h>
@@ -108,3 +109,37 @@  static void fixup_winbond_82c105(struct pci_dev* dev)
 }
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_WINBOND, PCI_DEVICE_ID_WINBOND_82C105,
 			 fixup_winbond_82c105);
+
+int pcibios_get_speed_cap_mask(struct pci_dev *dev, u32 *mask)
+{
+	struct device_node *dn, *pdn;
+	const uint32_t *pcie_link_speed_stats = NULL;
+
+	*mask = 0;
+	dn = pci_bus_to_OF_node(dev->bus);
+
+	/* Find nearest ibm,pcie-link-speed-stats, walking up the device tree */
+	for (pdn = dn; pdn != NULL; pdn = pdn->parent) {
+		pcie_link_speed_stats = (const uint32_t *) of_get_property(pdn,
+			"ibm,pcie-link-speed-stats", NULL);
+		if (pcie_link_speed_stats != NULL)
+			break;
+	}
+
+	if (pcie_link_speed_stats == NULL) {
+		dev_info(&dev->dev, "no ibm,pcie-link-speed-stats property\n");
+		return -EINVAL;
+	}
+
+	switch (pcie_link_speed_stats[0]) {
+	case 0x02:
+		*mask |= PCIE_SPEED_50;
+	case 0x01:
+		*mask |= PCIE_SPEED_25;
+	case 0x00:
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}