[PATCH v2 01/17] PCI/DPC: Allocate the DPC save buffer during device setup

[David Matlack <dmatlack@google.com>]

Allocate the DPC capability's save buffer in pci_dpc_init() rather than
in dpc_probe(), and report an allocation failure, which dpc_probe()
ignored.

dpc_probe() runs when the portdrv DPC service binds to a port, which is
long after the device has been added, and does not happen at all if the
service is not enabled. Until then pci_save_dpc_state() silently saves
nothing, so a reset in that window loses the DPC Control register.

Allocating during device setup makes buffer existence depend only on the
capability being present, which is what the save and restore paths
already assume. It also puts every capability save buffer in one phase
of a device's life, which a later patch relies on.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/pci/pcie/dpc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 2b779bd1d861..b7f79266f66d 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -408,6 +408,9 @@ void pci_dpc_init(struct pci_dev *pdev)
 	if (!pdev->dpc_cap)
 		return;
 
+	if (pci_add_ext_cap_save_buffer(pdev, PCI_EXT_CAP_ID_DPC, sizeof(u16)))
+		pci_err(pdev, "unable to allocate suspend buffer for DPC\n");
+
 	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CAP, &cap);
 	if (!(cap & PCI_EXP_DPC_CAP_RP_EXT))
 		return;
@@ -499,7 +502,6 @@ static int dpc_probe(struct pcie_device *dev)
 		 FLAG(cap, PCI_EXP_DPC_CAP_SW_TRIGGER), pdev->dpc_rp_log_size,
 		 FLAG(cap, PCI_EXP_DPC_CAP_DL_ACTIVE));
 
-	pci_add_ext_cap_save_buffer(pdev, PCI_EXT_CAP_ID_DPC, sizeof(u16));
 	return status;
 }
 
-- 
2.56.0.455.g6c5a503b38-goog