[PATCH] PCI: mediatek-gen3: handle PERST after reset

[Frank Wunderlich]

From: Frank Wunderlich <frank-w@xxxxxxxxxxxxxxx>

De-assert PERST in separate step after reset signals to fully comply
the PCIe CEM clause 2.2.

This fixes some NVME detection issues on mt7986.

Fixes: d3bf75b579b9 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
Signed-off-by: Frank Wunderlich <frank-w@xxxxxxxxxxxxxxx>
---
Patch is taken from user Ruslan aka RRKh61 (permitted me to send it
with me as author).

https://forum.banana-pi.org/t/bpi-r3-nvme-connection-issue/14563/17
---
 drivers/pci/controller/pcie-mediatek-gen3.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
index b8612ce5f4d0..176b1a04565d 100644
--- a/drivers/pci/controller/pcie-mediatek-gen3.c
+++ b/drivers/pci/controller/pcie-mediatek-gen3.c
@@ -350,7 +350,13 @@ static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie)
 	msleep(100);
 
 	/* De-assert reset signals */
-	val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB);
+	val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB);
+	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+
+	msleep(100);
+
+	/* De-assert PERST# signals */
+	val &= ~(PCIE_PE_RSTB);
 	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
 
 	/* Check if the link is up or not */
-- 
2.34.1