[PATCH 1/2] PCI: meson: Fix PERST# timing by asserting reset before LTSSM enable

[Gowtham Kudupudi]

On warm reboot, the PCIe controller's LTSSM starts link training
immediately if PERST# is already deasserted from the previous boot.
The driver then pulses PERST# for only 500us, which is too short to
properly reset the endpoint device that has already started training.

Fix by moving the PERST# assert/deassert pulse BEFORE enabling LTSSM,
so the endpoint gets a clean reset cycle before link training begins.

This was found on Amlogic G12B (A311D) with NVMe on an M.2 slot.
Cold boot worked because POR held PERST# low; warm reboot did not.
The fix was confirmed on a Banana Pi CM4 with Waveshare IO base board.

Signed-off-by: Gowtham Kudupudi <gowtham@xxxxxxxxxxxxx>
---
 drivers/pci/controller/dwc/pci-meson.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pci-meson.c b/drivers/pci/controller/dwc/pci-meson.c
index 0694084f612..c28ab40c9ff 100644
--- a/drivers/pci/controller/dwc/pci-meson.c
+++ b/drivers/pci/controller/dwc/pci-meson.c
@@ -308,8 +308,8 @@ static int meson_pcie_start_link(struct dw_pcie *pci)
 {
 	struct meson_pcie *mp = to_meson_pcie(pci);
 
-	meson_pcie_ltssm_enable(mp);
 	meson_pcie_assert_reset(mp);
+	meson_pcie_ltssm_enable(mp);
 
 	return 0;
 }
-- 
2.54.0


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