[PATCH v3 1/2] PCI: rockchip-host: Fix rockchip_pcie_host_init_port() PERST# handling

Damien Le Moal
2024-04-12T02:37:38Z

The PCIe specifications (PCI Express Electromechanical Specification rev
2.0, section 2.6.2) 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 bringing back PESRT# signal to high 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@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