linux-kernel - [PATCH 1/2] PCI: dwc: Add new accessors to enable/disable DBI CS2 while setting the BAR size

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Message-Id: <20231017-pcie-qcom-bar-v1-1-3e26de07bec0@linaro.org>
Date:   Tue, 17 Oct 2023 11:47:54 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Manivannan Sadhasivam <mani@...nel.org>
Subject: [PATCH 1/2] PCI: dwc: Add new accessors to enable/disable DBI CS2
 while setting the BAR size

From: Manivannan Sadhasivam <mani@...nel.org>

As per the DWC databook v4.21a, section M.4.1, in order to write some read
only and shadow registers through application DBI, the device driver should
assert DBI Chip Select 2 (CS2) in addition to DBI Chip Select (CS).

This is a requirement at least on the Qcom platforms while programming the
BAR size, as the BAR mask registers are marked RO. So let's add two new
accessors dw_pcie_dbi_cs2_{en/dis} to enable/disable CS2 access in a vendor
specific way while programming the BAR size.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/controller/dwc/pcie-designware-ep.c |  6 ++++++
 drivers/pci/controller/dwc/pcie-designware.h    | 13 +++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index d34a5e87ad18..1874fb3d8df4 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -269,11 +269,17 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 
 	dw_pcie_dbi_ro_wr_en(pci);
 
+	dw_pcie_dbi_cs2_en(pci);
 	dw_pcie_writel_dbi2(pci, reg_dbi2, lower_32_bits(size - 1));
+	dw_pcie_dbi_cs2_dis(pci);
+
 	dw_pcie_writel_dbi(pci, reg, flags);
 
 	if (flags & PCI_BASE_ADDRESS_MEM_TYPE_64) {
+		dw_pcie_dbi_cs2_en(pci);
 		dw_pcie_writel_dbi2(pci, reg_dbi2 + 4, upper_32_bits(size - 1));
+		dw_pcie_dbi_cs2_dis(pci);
+
 		dw_pcie_writel_dbi(pci, reg + 4, 0);
 	}
 
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 55ff76e3d384..3cba27b5bbe5 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -379,6 +379,7 @@ struct dw_pcie_ops {
 			     size_t size, u32 val);
 	void    (*write_dbi2)(struct dw_pcie *pcie, void __iomem *base, u32 reg,
 			      size_t size, u32 val);
+	void	(*dbi_cs2_access)(struct dw_pcie *pcie, bool enable);
 	int	(*link_up)(struct dw_pcie *pcie);
 	enum dw_pcie_ltssm (*get_ltssm)(struct dw_pcie *pcie);
 	int	(*start_link)(struct dw_pcie *pcie);
@@ -508,6 +509,18 @@ static inline void dw_pcie_dbi_ro_wr_dis(struct dw_pcie *pci)
 	dw_pcie_writel_dbi(pci, reg, val);
 }
 
+static inline void dw_pcie_dbi_cs2_en(struct dw_pcie *pci)
+{
+	if (pci->ops && pci->ops->dbi_cs2_access)
+		pci->ops->dbi_cs2_access(pci, true);
+}
+
+static inline void dw_pcie_dbi_cs2_dis(struct dw_pcie *pci)
+{
+	if (pci->ops && pci->ops->dbi_cs2_access)
+		pci->ops->dbi_cs2_access(pci, false);
+}
+
 static inline int dw_pcie_start_link(struct dw_pcie *pci)
 {
 	if (pci->ops && pci->ops->start_link)

-- 
2.25.1