[PATCH v2 1/1] PCI: qcom-ep: Implement write_dbi2() callback for writing DBI2 registers properly

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DWC core driver exposes the write_dbi2() callback for writing to the DBI2
registers in a vendor specific way. On the Qcom EP plaforms, DBI_CS2 bit in
the ELBI region needs to be asserted before writing to any DBI2 registers
and deasserted once done. So let's implement the callback for the Qcom PCIe
EP driver so that the DBI2 writes are handled properly in the hardware.

Without this callback, DBI2 register writes like BAR size won't go through
and as a result, the default BAR size is set for all BARs.

Cc: stable@xxxxxxxxxxxxxxx # 5.16+
Fixes: f55fee56a631 ("PCI: qcom-ep: Add Qualcomm PCIe Endpoint controller driver")
Suggested-by: Serge Semin <fancer.lancer@xxxxxxxxx>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
 drivers/pci/controller/dwc/pcie-qcom-ep.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
index 32c8d9e37876..7da0599f70e7 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
@@ -124,6 +124,7 @@
 /* ELBI registers */
 #define ELBI_SYS_STTS				0x08
+#define ELBI_CS2_ENABLE				0xa4
 /* DBI registers */
 #define DBI_CON_STATUS				0x44
@@ -262,6 +263,21 @@ static void qcom_pcie_dw_stop_link(struct dw_pcie *pci)
+static void qcom_pcie_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);
+	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);
 static void qcom_pcie_ep_icc_update(struct qcom_pcie_ep *pcie_ep)
 	struct dw_pcie *pci = &pcie_ep->pci;
@@ -500,6 +516,7 @@ static const struct dw_pcie_ops pci_ops = {
 	.link_up = qcom_pcie_dw_link_up,
 	.start_link = qcom_pcie_dw_start_link,
 	.stop_link = qcom_pcie_dw_stop_link,
+	.write_dbi2 = qcom_pcie_write_dbi2,
 static int qcom_pcie_ep_get_io_resources(struct platform_device *pdev,

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