[PATCH v4 1/2] PCI: rockchip-host: Fix rockchip_pcie_host_init_port() PERST# handling

[Damien Le Moal]

The PCIe specifications (PCIe CEM r5.1, sec 2.9.2) mandate that the
PERST# signal must remain asserted for at least 100 usec (Tperst-clk)
after the PCIe reference clock becomes stable (if a reference clock is
supplied), and for at least 100 msec after the power is stable (Tpvperl,
defined by the macro PCIE_T_PVPERL_MS).

Modify rockchip_pcie_host_init_port() to satisfy these constraints by
adding a sleep period before deasserting PERST# using the ep_gpio GPIO.
Since Tperst-clk is the shorter wait time, add an msleep() call for the
longer PCIE_T_PVPERL_MS milliseconds to handle both timing requirements.

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

diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
index 300b9dc85ecc..fc868251e570 100644
--- a/drivers/pci/controller/pcie-rockchip-host.c
+++ b/drivers/pci/controller/pcie-rockchip-host.c
@@ -322,6 +322,7 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
 	rockchip_pcie_write(rockchip, PCIE_CLIENT_LINK_TRAIN_ENABLE,
 			    PCIE_CLIENT_CONFIG);
 
+	msleep(PCIE_T_PVPERL_MS);
 	gpiod_set_value_cansleep(rockchip->ep_gpio, 1);
 
 	/* 500ms timeout value should be enough for Gen1/2 training */
-- 
2.44.0