linux-kernel - [PATCH V13 03/12] PCI: dwc: Perform dbi regs write lock towards the end

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Message-ID: <20190710062212.1745-4-vidyas@nvidia.com>
Date:   Wed, 10 Jul 2019 11:52:03 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <lorenzo.pieralisi@....com>, <bhelgaas@...gle.com>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <kishon@...com>, <catalin.marinas@....com>, <will.deacon@....com>,
        <jingoohan1@...il.com>, <gustavo.pimentel@...opsys.com>
CC:     <digetx@...il.com>, <mperttunen@...dia.com>,
        <linux-pci@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <kthota@...dia.com>,
        <mmaddireddy@...dia.com>, <vidyas@...dia.com>, <sagar.tv@...il.com>
Subject: [PATCH V13 03/12] PCI: dwc: Perform dbi regs write lock towards the end

Some of DesignWare core's DBI registers (a.k.a configuration space
registers) are write-protected with a lock without enabling which they are
read-only by default. These write-protected registers are implementation
specific. Tegra194's BAR-0 register which is at offset 0x10 in the
configuration space is an example. Current implementation in
dw_pcie_setup_rc() API attempts to unlock those write-protected registers
whenever they are updated and lock them back again for writing. This patch
attempts to unlock all such write-protected registers for writing in the
beginning of the API once and lock them back again towards the end to avoid
bloating the API with multiple unlock/lock sequences for all those
write-protected registers.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
Reviewed-by: Thierry Reding <treding@...dia.com>
Acked-by: Jingoo Han <jingoohan1@...il.com>
---
V13:
* None

V12:
* Modified commit message to make it explicit that write-protected registers are
  implementation specific.

V11:
* None

V10:
* None

V9:
* None

V8:
* None

V7:
* None

V6:
* Moved write enable to the beginning of the API and write disable to the end

V5:
* None

V4:
* None

V3:
* None

V2:
* None

 drivers/pci/controller/dwc/pcie-designware-host.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index f93252d0da5b..d3156446ff27 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -628,6 +628,12 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
 	u32 val, ctrl, num_ctrls;
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 
+	/*
+	 * Enable DBI read-only registers for writing/updating configuration.
+	 * Write permission gets disabled towards the end of this function.
+	 */
+	dw_pcie_dbi_ro_wr_en(pci);
+
 	dw_pcie_setup(pci);
 
 	if (!pp->ops->msi_host_init) {
@@ -650,12 +656,10 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
 	dw_pcie_writel_dbi(pci, PCI_BASE_ADDRESS_1, 0x00000000);
 
 	/* Setup interrupt pins */
-	dw_pcie_dbi_ro_wr_en(pci);
 	val = dw_pcie_readl_dbi(pci, PCI_INTERRUPT_LINE);
 	val &= 0xffff00ff;
 	val |= 0x00000100;
 	dw_pcie_writel_dbi(pci, PCI_INTERRUPT_LINE, val);
-	dw_pcie_dbi_ro_wr_dis(pci);
 
 	/* Setup bus numbers */
 	val = dw_pcie_readl_dbi(pci, PCI_PRIMARY_BUS);
@@ -687,15 +691,13 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
 
 	dw_pcie_wr_own_conf(pp, PCI_BASE_ADDRESS_0, 4, 0);
 
-	/* Enable write permission for the DBI read-only register */
-	dw_pcie_dbi_ro_wr_en(pci);
 	/* Program correct class for RC */
 	dw_pcie_wr_own_conf(pp, PCI_CLASS_DEVICE, 2, PCI_CLASS_BRIDGE_PCI);
-	/* Better disable write permission right after the update */
-	dw_pcie_dbi_ro_wr_dis(pci);
 
 	dw_pcie_rd_own_conf(pp, PCIE_LINK_WIDTH_SPEED_CONTROL, 4, &val);
 	val |= PORT_LOGIC_SPEED_CHANGE;
 	dw_pcie_wr_own_conf(pp, PCIE_LINK_WIDTH_SPEED_CONTROL, 4, val);
+
+	dw_pcie_dbi_ro_wr_dis(pci);
 }
 EXPORT_SYMBOL_GPL(dw_pcie_setup_rc);
-- 
2.17.1