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From:   Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Date:   Tue, 17 Oct 2023 11:47:55 +0530
Subject: [PATCH 2/2] PCI: qcom-ep: Implement dbi_cs2_access() function
 callback for DBI CS2 access
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Message-Id: <20231017-pcie-qcom-bar-v1-2-3e26de07bec0@linaro.org>
References: <20231017-pcie-qcom-bar-v1-0-3e26de07bec0@linaro.org>
In-Reply-To: <20231017-pcie-qcom-bar-v1-0-3e26de07bec0@linaro.org>
To:     Jingoo Han <jingoohan1@gmail.com>,
        Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
        Manivannan Sadhasivam <mani@kernel.org>,
        Lorenzo Pieralisi <lpieralisi@kernel.org>,
        =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= <kw@linux.com>,
        Rob Herring <robh@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>
Cc:     linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-msm@vger.kernel.org,
        Manivannan Sadhasivam <mani@kernel.org>
Precedence: bulk

From: Manivannan Sadhasivam <mani@kernel.org>

Qcom EP platforms require enabling/disabling the DBI CS2 access while
programming some read only and shadow registers through DBI. So let's
implement the dbi_cs2_access() callback that will be called by the DWC core
while programming such registers like BAR mask register.

Without DBI CS2 access, writes to those registers will not be reflected.

Fixes: f55fee56a631 ("PCI: qcom-ep: Add Qualcomm PCIe Endpoint controller driver")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/pci/controller/dwc/pcie-qcom-ep.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
index 32c8d9e37876..4653cbf7f9ed 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 +263,18 @@ static void qcom_pcie_dw_stop_link(struct dw_pcie *pci)
 	disable_irq(pcie_ep->perst_irq);
 }
 
+static void qcom_pcie_dbi_cs2_access(struct dw_pcie *pci, bool enable)
+{
+	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
+
+	writel_relaxed(enable, pcie_ep->elbi + ELBI_CS2_ENABLE);
+	/*
+	 * Do a dummy read to make sure that the previous write has reached the
+	 * memory before returning.
+	 */
+	readl_relaxed(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 +513,7 @@ 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,
+	.dbi_cs2_access = qcom_pcie_dbi_cs2_access,
 };
 
 static int qcom_pcie_ep_get_io_resources(struct platform_device *pdev,

-- 
2.25.1