[PATCH V15 03/13] PCI: dwc: Perform dbi regs write lock towards the end

[Vidya Sagar]

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 <vid...@nvidia.com>
Reviewed-by: Thierry Reding <tred...@nvidia.com>
Acked-by: Jingoo Han <jingooh...@gmail.com>
---
V15:
* None

V14:
* None

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