[PATCH] PCI: qcom: Disable ASPM L0s for SA8775P

[Shawn Guo]

Commit f5cd8a929c82 ("PCI: dwc: Remove MSI/MSIX capability for Root Port
if iMSI-RX is used as MSI controller") removed MSI/MSI-X capabilities
from the Root Port on platforms using iMSI-RX (including SA8775P, which
has no msi-parent/msi-map in DT).  This causes PME and AER service
drivers to fall back from MSI to INTx.

With INTx-based PME active, the QCN9100 modem endpoint sends PME messages
during D-state transitions early in boot.  The level-triggered INTx
assertion coincides with ASPM L0s exit sequencing on SA8775P hardware,
causing Data Link Layer Replay Timer Timeout errors on both sides of the
link.

[   13.069528] pcieport 0000:00:00.0: PME: Signaling with IRQ 332
[   13.082436] pcieport 0000:00:00.0: AER: enabled with IRQ 332
[   13.082447] pcieport 0000:00:00.0: AER: Correctable error message received from 0000:01:00.0
[   13.101347] pci 0000:01:00.0: PCIe Bus Error: severity=Correctable, type=Data Link Layer, (Transmitter ID)
[   13.111281] pci 0000:01:00.0:   device [17cb:1103] error status/mask=00001000/0000e000
[   13.111284] pci 0000:01:00.0:    [12] Timeout
[   13.111313] pcieport 0000:00:00.0: AER: Multiple Correctable error message received from 0000:01:00.0
[   13.130512] pcieport 0000:00:00.0: PCIe Bus Error: severity=Correctable, type=Data Link Layer, (Transmitter ID)
[   13.130514] pcieport 0000:00:00.0:   device [17cb:0115] error status/mask=00001000/0000e000
[   13.130516] pcieport 0000:00:00.0:    [12] Timeout

Fix the PCIe regression on SA8775P/Lemans platform by adding no_l0s = true
to cfg_1_34_0 for SA8775P, so that PCI_EXP_LNKCAP_ASPM_L0S is cleared from
the Root Port and ASPM L0s is prevented from being negotiated.

Fixes: f5cd8a929c82 ("PCI: dwc: Remove MSI/MSIX capability for Root Port if iMSI-RX is used as MSI controller")
Assisted-by: Claude:claude-4-6-sonnet
Signed-off-by: Shawn Guo <shengchao.guo@xxxxxxxxxxxxxxxx>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index af6bf5cce65b..6a14b5091338 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1473,6 +1473,7 @@ static const struct qcom_pcie_cfg cfg_1_9_0 = {
 static const struct qcom_pcie_cfg cfg_1_34_0 = {
 	.ops = &ops_1_9_0,
 	.override_no_snoop = true,
+	.no_l0s = true,
 };
 
 static const struct qcom_pcie_cfg cfg_2_1_0 = {
-- 
2.43.0