[PATCH] PCI: rockchip-host: Fix rockchip_pcie_host_init_port() PERST handling

[Damien Le Moal <dlemoal@kernel.org>]

The PCI specifications mandate that PERST be asserted for at least
100ms. Make sure that is done in rockchip_pcie_host_init_port() by
adding a 100ms sleep before bringing back PESRT signal to high using the
ep_gpio GPIO. Comments are also added to clarify this behavior.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
---
 drivers/pci/controller/pcie-rockchip-host.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
index 300b9dc85ecc..d526b9d26c18 100644
--- a/drivers/pci/controller/pcie-rockchip-host.c
+++ b/drivers/pci/controller/pcie-rockchip-host.c
@@ -294,6 +294,7 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
 	int err, i = MAX_LANE_NUM;
 	u32 status;
 
+	/* Assert PERST */
 	gpiod_set_value_cansleep(rockchip->ep_gpio, 0);
 
 	err = rockchip_pcie_init_port(rockchip);
@@ -322,6 +323,11 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
 	rockchip_pcie_write(rockchip, PCIE_CLIENT_LINK_TRAIN_ENABLE,
 			    PCIE_CLIENT_CONFIG);
 
+	/*
+	 * PCIe specifications mandate that PERST be asserted for at
+	 * least 100ms.
+	 */
+	msleep(100);
 	gpiod_set_value_cansleep(rockchip->ep_gpio, 1);
 
 	/* 500ms timeout value should be enough for Gen1/2 training */
-- 
2.44.0