PCI: rockchip-host: Wait 100ms after reset before starting configuration

PCIe r6.0, sec 6.6.1, states that the host should wait for at least 100
msec from the end of a conventional reset (PERST# is de-asserted) before
sending a configuration request to ensure that the device is able to
respond with a "Request Retry Status" completion.

Add the PCIE_T_RRS_READY_MS macro to define this wait time and modify
rockchip_pcie_host_init_port() to add this 100ms sleep after deasserting
PERST# using the ep_gpio GPIO.

Link: https://lore.kernel.org/linux-pci/20240413004120.1099089-3-dlemoal@kernel.org
Suggested-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Author: damien-lemoal

drivers/pci/controller/pcie-rockchip-host.c

@@ -325,6 +325,8 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
 	msleep(PCIE_T_PVPERL_MS);
 	gpiod_set_value_cansleep(rockchip->ep_gpio, 1);
 
+	msleep(PCIE_T_RRS_READY_MS);
+
 	/* 500ms timeout value should be enough for Gen1/2 training */
 	err = readl_poll_timeout(rockchip->apb_base + PCIE_CLIENT_BASIC_STATUS1,
 				 status, PCIE_LINK_UP(status), 20,

drivers/pci/pci.h

@@ -16,6 +16,13 @@
 /* Power stable to PERST# inactive from PCIe card Electromechanical Spec */
 #define PCIE_T_PVPERL_MS		100
 
+/*
+ * End of conventional reset (PERST# de-asserted) to first configuration
+ * request (device able to respond with a "Request Retry Status" completion),
+ * from PCIe r6.0, sec 6.6.1.
+ */
+#define PCIE_T_RRS_READY_MS	100
+
 /*
  * PCIe r6.0, sec 5.3.3.2.1 <PME Synchronization>
  * Recommends 1ms to 10ms timeout to check L2 ready.