[PATCH v5 2/3] PCI: dwc: Force L2 link entry on shutdown/reboot without D3cold check

[Krishna Chaitanya Chundru]

dw_pcie_suspend_noirq() normally calls pci_host_common_d3cold_possible()
to check whether every downstream endpoint can be put into D3cold before
bothering to move the link to L2. If no endpoint supports it, the
function returns early and leaves the link up.

Querying D3cold support during shutdown is actively harmful, not just
slow: pci_host_common_d3cold_possible() requires every active endpoint
to already be in PCI_D3hot, and returns false otherwise. If any endpoint
is still in D0 -- which is common, since endpoint drivers aren't
guaranteed to have suspended by the time the host's shutdown path runs
the check fails and dw_pcie_suspend_noirq() returns early without ever
moving the link to L2, leaving it up right up to the point where the
system cuts power/clocks to the controller.

Add a "force_d3cold" flag to struct dw_pcie_rp that callers set
explicitly to force this behavior, rather than having
dw_pcie_suspend_noirq() infer the shutdown/reboot case itself from
system_state. Still call pci_host_common_d3cold_possible()
unconditionally, since it's also how "pme_capable" gets set, but ignore
its return value when force_d3cold is set and force L2 entry regardless.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx>
---
 drivers/pci/controller/dwc/pcie-designware-host.c | 5 +++--
 drivers/pci/controller/dwc/pcie-designware.h      | 1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index f5a38e6fd8d7..a8a3861c2956 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -1224,14 +1224,15 @@ static int dw_pcie_pme_turn_off(struct dw_pcie *pci)
 
 int dw_pcie_suspend_noirq(struct dw_pcie *pci)
 {
-	bool pme_capable = false;
+	bool d3cold, pme_capable = false;
 	int ret = 0;
 	u32 val;
 
 	if (!dw_pcie_link_up(pci))
 		goto stop_link;
 
-	if (!pci_host_common_d3cold_possible(pci->pp.bridge, &pme_capable))
+	d3cold = pci_host_common_d3cold_possible(pci->pp.bridge, &pme_capable);
+	if (!d3cold && !pci->pp.force_d3cold)
 		return 0;
 
 	if (pci->pp.ops->pme_turn_off) {
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index a53ac27cd244..8becf4e62703 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -471,6 +471,7 @@ struct dw_pcie_rp {
 	bool			native_ecam;
 	bool                    skip_l23_ready;
 	bool			skip_pwrctrl_off;
+	bool			force_d3cold;
 };
 
 struct dw_pcie_ep_ops {

-- 
2.34.1