PCI: dw-rockchip: Add rockchip_pcie_get_ltssm() helper

Add a rockchip_pcie_ltssm() helper function that reads the LTSSM status.

This helper will be used in additional places in follow-up commits.

Link: https://lore.kernel.org/linux-pci/20240607-rockchip-pcie-ep-v1-v5-8-0a042d6b0049@kernel.orgSigned-off-by: Niklas Cassel <cassel@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>

drivers/pci/controller/dwc/pcie-dw-rockchip.c

@@ -143,6 +143,11 @@ static int rockchip_pcie_init_irq_domain(struct rockchip_pcie *rockchip)
 	return 0;
 }
 
+static u32 rockchip_pcie_get_ltssm(struct rockchip_pcie *rockchip)
+{
+	return rockchip_pcie_readl_apb(rockchip, PCIE_CLIENT_LTSSM_STATUS);
+}
+
 static void rockchip_pcie_enable_ltssm(struct rockchip_pcie *rockchip)
 {
 	rockchip_pcie_writel_apb(rockchip, PCIE_CLIENT_ENABLE_LTSSM,
@@ -152,7 +157,7 @@ static void rockchip_pcie_enable_ltssm(struct rockchip_pcie *rockchip)
 static int rockchip_pcie_link_up(struct dw_pcie *pci)
 {
 	struct rockchip_pcie *rockchip = to_rockchip_pcie(pci);
-	u32 val = rockchip_pcie_readl_apb(rockchip, PCIE_CLIENT_LTSSM_STATUS);
+	u32 val = rockchip_pcie_get_ltssm(rockchip);
 
 	if ((val & PCIE_LINKUP) == PCIE_LINKUP &&
 	    (val & PCIE_LTSSM_STATUS_MASK) == PCIE_L0S_ENTRY)