Revert "PCI: qcom: Prepare for the DWC ECAM enablement"

This reverts commit 4660e50.

Commit f6fd357 ("PCI: dwc: Prepare the driver for enabling ECAM
mechanism using iATU 'CFG Shift Feature'") enabled ECAM access by using
the config space start as DBI address.

However, this approach breaks vendor drivers that rely on the DBI address
for internal accesses, especially when the vendor config space is 256MB
aligned.

To resolve this, avoid using the DBI as the start of config space and
instead introduce a custom ECAM PCI ops implementation.

Revert the qcom specific ECAM preparation logic in 4660e50 ("PCI:
qcom: Prepare for the DWC ECAM enablement") since it's no longer necessary.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251017-ecam_fix-v1-2-f6faa3d0edf3@oss.qualcomm.com

Author: krishnachaitanya-linux

drivers/pci/controller/dwc/pcie-qcom.c

@@ -55,7 +55,6 @@
 #define PARF_AXI_MSTR_WR_ADDR_HALT_V2		0x1a8
 #define PARF_Q2A_FLUSH				0x1ac
 #define PARF_LTSSM				0x1b0
-#define PARF_SLV_DBI_ELBI			0x1b4
 #define PARF_INT_ALL_STATUS			0x224
 #define PARF_INT_ALL_CLEAR			0x228
 #define PARF_INT_ALL_MASK			0x22c
@@ -65,16 +64,6 @@
 #define PARF_DBI_BASE_ADDR_V2_HI		0x354
 #define PARF_SLV_ADDR_SPACE_SIZE_V2		0x358
 #define PARF_SLV_ADDR_SPACE_SIZE_V2_HI		0x35c
-#define PARF_BLOCK_SLV_AXI_WR_BASE		0x360
-#define PARF_BLOCK_SLV_AXI_WR_BASE_HI		0x364
-#define PARF_BLOCK_SLV_AXI_WR_LIMIT		0x368
-#define PARF_BLOCK_SLV_AXI_WR_LIMIT_HI		0x36c
-#define PARF_BLOCK_SLV_AXI_RD_BASE		0x370
-#define PARF_BLOCK_SLV_AXI_RD_BASE_HI		0x374
-#define PARF_BLOCK_SLV_AXI_RD_LIMIT		0x378
-#define PARF_BLOCK_SLV_AXI_RD_LIMIT_HI		0x37c
-#define PARF_ECAM_BASE				0x380
-#define PARF_ECAM_BASE_HI			0x384
 #define PARF_NO_SNOOP_OVERRIDE			0x3d4
 #define PARF_ATU_BASE_ADDR			0x634
 #define PARF_ATU_BASE_ADDR_HI			0x638
@@ -98,7 +87,6 @@
 
 /* PARF_SYS_CTRL register fields */
 #define MAC_PHY_POWERDOWN_IN_P2_D_MUX_EN	BIT(29)
-#define PCIE_ECAM_BLOCKER_EN			BIT(26)
 #define MST_WAKEUP_EN				BIT(13)
 #define SLV_WAKEUP_EN				BIT(12)
 #define MSTR_ACLK_CGC_DIS			BIT(10)
@@ -146,9 +134,6 @@
 /* PARF_LTSSM register fields */
 #define LTSSM_EN				BIT(8)
 
-/* PARF_SLV_DBI_ELBI */
-#define SLV_DBI_ELBI_ADDR_BASE			GENMASK(11, 0)
-
 /* PARF_INT_ALL_{STATUS/CLEAR/MASK} register fields */
 #define PARF_INT_ALL_LINK_UP			BIT(13)
 #define PARF_INT_MSI_DEV_0_7			GENMASK(30, 23)
@@ -326,47 +311,6 @@ static void qcom_ep_reset_deassert(struct qcom_pcie *pcie)
 	qcom_perst_assert(pcie, false);
 }
 
-static void qcom_pci_config_ecam(struct dw_pcie_rp *pp)
-{
-	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
-	struct qcom_pcie *pcie = to_qcom_pcie(pci);
-	u64 addr, addr_end;
-	u32 val;
-
-	writel_relaxed(lower_32_bits(pci->dbi_phys_addr), pcie->parf + PARF_ECAM_BASE);
-	writel_relaxed(upper_32_bits(pci->dbi_phys_addr), pcie->parf + PARF_ECAM_BASE_HI);
-
-	/*
-	 * The only device on the root bus is a single Root Port. If we try to
-	 * access any devices other than Device/Function 00.0 on Bus 0, the TLP
-	 * will go outside of the controller to the PCI bus. But with CFG Shift
-	 * Feature (ECAM) enabled in iATU, there is no guarantee that the
-	 * response is going to be all F's. Hence, to make sure that the
-	 * requester gets all F's response for accesses other than the Root
-	 * Port, configure iATU to block the transactions starting from
-	 * function 1 of the root bus to the end of the root bus (i.e., from
-	 * dbi_base + 4KB to dbi_base + 1MB).
-	 */
-	addr = pci->dbi_phys_addr + SZ_4K;
-	writel_relaxed(lower_32_bits(addr), pcie->parf + PARF_BLOCK_SLV_AXI_WR_BASE);
-	writel_relaxed(upper_32_bits(addr), pcie->parf + PARF_BLOCK_SLV_AXI_WR_BASE_HI);
-
-	writel_relaxed(lower_32_bits(addr), pcie->parf + PARF_BLOCK_SLV_AXI_RD_BASE);
-	writel_relaxed(upper_32_bits(addr), pcie->parf + PARF_BLOCK_SLV_AXI_RD_BASE_HI);
-
-	addr_end = pci->dbi_phys_addr + SZ_1M - 1;
-
-	writel_relaxed(lower_32_bits(addr_end), pcie->parf + PARF_BLOCK_SLV_AXI_WR_LIMIT);
-	writel_relaxed(upper_32_bits(addr_end), pcie->parf + PARF_BLOCK_SLV_AXI_WR_LIMIT_HI);
-
-	writel_relaxed(lower_32_bits(addr_end), pcie->parf + PARF_BLOCK_SLV_AXI_RD_LIMIT);
-	writel_relaxed(upper_32_bits(addr_end), pcie->parf + PARF_BLOCK_SLV_AXI_RD_LIMIT_HI);
-
-	val = readl_relaxed(pcie->parf + PARF_SYS_CTRL);
-	val |= PCIE_ECAM_BLOCKER_EN;
-	writel_relaxed(val, pcie->parf + PARF_SYS_CTRL);
-}
-
 static int qcom_pcie_start_link(struct dw_pcie *pci)
 {
 	struct qcom_pcie *pcie = to_qcom_pcie(pci);
@@ -1320,7 +1264,6 @@ static int qcom_pcie_host_init(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct qcom_pcie *pcie = to_qcom_pcie(pci);
-	u16 offset;
 	int ret;
 
 	qcom_ep_reset_assert(pcie);
@@ -1329,17 +1272,6 @@ static int qcom_pcie_host_init(struct dw_pcie_rp *pp)
 	if (ret)
 		return ret;
 
-	if (pp->ecam_enabled) {
-		/*
-		 * Override ELBI when ECAM is enabled, as when ECAM is enabled,
-		 * ELBI moves under the 'config' space.
-		 */
-		offset = FIELD_GET(SLV_DBI_ELBI_ADDR_BASE, readl(pcie->parf + PARF_SLV_DBI_ELBI));
-		pci->elbi_base = pci->dbi_base + offset;
-
-		qcom_pci_config_ecam(pp);
-	}
-
 	ret = qcom_pcie_phy_power_on(pcie);
 	if (ret)
 		goto err_deinit;