PCI: imx6: Delay link start until configfs 'start' written

According to Documentation/PCI/endpoint/pci-endpoint-cfs.rst, the Endpoint
controller (EPC) should only start the link when userspace writes '1' to
the '/sys/kernel/config/pci_ep/controllers/<EPC>/start' attribute, which
ultimately results in calling imx_pcie_start_link() via
pci_epc_start_store().

To align with the documented behavior, do not start the link automatically
when adding the EP controller.

Fixes: 75c2f26 ("PCI: imx6: Add i.MX PCIe EP mode support")
Signed-off-by: Richard Zhu <[email protected]>
[mani: reworded commit subject and description]
Signed-off-by: Manivannan Sadhasivam <[email protected]>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Frank Li <[email protected]>
Cc: [email protected]
Link: https://patch.msgid.link/[email protected]

Author: Richard Zhu

drivers/pci/controller/dwc/pci-imx6.c

@@ -1474,9 +1474,6 @@ static int imx_add_pcie_ep(struct imx_pcie *imx_pcie,
 
 	pci_epc_init_notify(ep->epc);
 
-	/* Start LTSSM. */
-	imx_pcie_ltssm_enable(dev);
-
 	return 0;
 }