Re: [PATCH 2/2] PCI: Add support for Enhanced Allocation devices

Thanks for taking a look Yinghai.

On Tue, Sep 01, 2015 at 04:14:08PM -0700, Yinghai Lu wrote:

On Thu, Aug 20, 2015 at 9:59 AM, Sean O. Stalley [off-list ref] wrote:

quoted

Add support for devices using Enhanced Allocation entries instead of BARs.
This patch allows the kernel to parse the EA Extended Capability structure
in PCI configspace and claim the BAR-equivalent resources.

Signed-off-by: Sean O. Stalley <redacted>
---
 drivers/pci/pci.c   | 219 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.h   |   1 +
 drivers/pci/probe.c |   3 +
 3 files changed, 223 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 0008c95..c8217a8 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c

...

quoted

+
+/* Read an Enhanced Allocation (EA) entry */
+static int pci_ea_read(struct pci_dev *dev, int offset)
+{

...

quoted

+       res->name = pci_name(dev);
+       res->start = start;
+       res->end = end;
+       res->flags = flags;
+
+       pci_ea_claim_resource(dev, res);
+
+out:
+       return offset + ent_size;
+}
+
+/* Enhanced Allocation Initalization */
+void pci_ea_init(struct pci_dev *dev)
+{

...

quoted

+
+       for (i = 0; i < num_ent; ++i) {
+               /* parse each EA entry */
+               dev_dbg(&dev->dev, "%s: parsing entry %i...\n", __func__, i);
+               offset = pci_ea_read(dev, offset);
+       }
+}
+
 static void pci_add_saved_cap(struct pci_dev *pci_dev,
        struct pci_cap_saved_state *new_cap)
 {

quoted

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index cefd636..4cadf35 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c

@@ -1522,6 +1522,9 @@ static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn)

 static void pci_init_capabilities(struct pci_dev *dev)
 {
+       /* Enhanced Allocation */
+       pci_ea_init(dev);
+
        /* MSI/MSI-X list */
        pci_msi_init_pci_dev(dev);

Should not call pci_ea_claim_resource() that early.

Out of curiosity, why shouldn't resources be claimed that early?
EA resources are fixed by hardware. They are always there & will never move.

For x86 and other arches, we call
pcibios_resource_survey/pcibios_allocate_bus_resouce/pcibios_allocate_resources
quite late.

Would it be better to modify pci_claim_resource() to support EA instead of adding pci_ea_claim_resource()?
That way, EA entries would be claimed at the same time as traditional BARs.

-Sean