PCI: dwc: Add support for ELBI resource mapping

External Local Bus Interface (ELBI) is an optional register space for all
DWC IPs containing the vendor specific registers. There is no need for the
vendor glue drivers to fetch and map the ELBI region separately.

Hence, optionally fetch and map the resource from DT in the DWC core. This
also warrants dropping the corresponding code from glue drivers. Hence,
drop the ELBI resource fetch and map logic from glue drivers and convert
them to use 'dw_pci::elbi_base'.

Note that the pcie-qcom-ep driver used devm_pci_remap_cfg_resource() to map
the ELBI resource previously. But it was a mistake since
devm_pci_remap_cfg_resource() should only be used for mapping the PCIe
config space region as it maps the region as Non-Posted. As ELBI is used to
hold vendor specific registers, there is no need to map the region as
Non-Posted. With this conversion, the region will get mapped as normal MMIO
memory.

Suggested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[mani: removed elbi override, converted glue drivers and reworded description]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20250923-controller-dwc-ecam-v10-1-e84390ba75fa@kernel.org

1 files changed, 3 insertions, 12 deletions

diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
index aaf060bf39d4..d7a7e278f682 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
@@ -179,7 +179,6 @@ struct qcom_pcie_ep_cfg {
  * struct qcom_pcie_ep - Qualcomm PCIe Endpoint Controller
  * @pci: Designware PCIe controller struct
  * @parf: Qualcomm PCIe specific PARF register base
- * @elbi: Designware PCIe specific ELBI register base
  * @mmio: MMIO register base
  * @perst_map: PERST regmap
  * @mmio_res: MMIO region resource
@@ -202,7 +201,6 @@ struct qcom_pcie_ep {
 	struct dw_pcie pci;
 
 	void __iomem *parf;
-	void __iomem *elbi;
 	void __iomem *mmio;
 	struct regmap *perst_map;
 	struct resource *mmio_res;
@@ -267,10 +265,9 @@ static void qcom_pcie_ep_configure_tcsr(struct qcom_pcie_ep *pcie_ep)
 
 static bool qcom_pcie_dw_link_up(struct dw_pcie *pci)
 {
-	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
 	u32 reg;
 
-	reg = readl_relaxed(pcie_ep->elbi + ELBI_SYS_STTS);
+	reg = readl_relaxed(pci->elbi_base + ELBI_SYS_STTS);
 
 	return reg & XMLH_LINK_UP;
 }
@@ -294,16 +291,15 @@ static void qcom_pcie_dw_stop_link(struct dw_pcie *pci)
 static void qcom_pcie_dw_write_dbi2(struct dw_pcie *pci, void __iomem *base,
 				    u32 reg, size_t size, u32 val)
 {
-	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
 	int ret;
 
-	writel(1, pcie_ep->elbi + ELBI_CS2_ENABLE);
+	writel(1, pci->elbi_base + ELBI_CS2_ENABLE);
 
 	ret = dw_pcie_write(pci->dbi_base2 + reg, size, val);
 	if (ret)
 		dev_err(pci->dev, "Failed to write DBI2 register (0x%x): %d\n", reg, ret);
 
-	writel(0, pcie_ep->elbi + ELBI_CS2_ENABLE);
+	writel(0, pci->elbi_base + ELBI_CS2_ENABLE);
 }
 
 static void qcom_pcie_ep_icc_update(struct qcom_pcie_ep *pcie_ep)
@@ -583,11 +579,6 @@ static int qcom_pcie_ep_get_io_resources(struct platform_device *pdev,
 		return PTR_ERR(pci->dbi_base);
 	pci->dbi_base2 = pci->dbi_base;
 
-	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "elbi");
-	pcie_ep->elbi = devm_pci_remap_cfg_resource(dev, res);
-	if (IS_ERR(pcie_ep->elbi))
-		return PTR_ERR(pcie_ep->elbi);
-
 	pcie_ep->mmio_res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
 							 "mmio");
 	if (!pcie_ep->mmio_res) {