[PATCH v3 02/13] PCI: dwc: Don't use generic IO-ops for DBI-space access

[Serge Semin <Sergey.Semin@baikalelectronics.ru>]

Commit c2b0c098fbd1 ("PCI: dwc: Use generic config accessors") replaced
the locally defined DW PCIe host controller config-space accessors with
the generic methods pci_generic_config_read() and
pci_generic_config_write(). It was intended that the corresponding
bus-mapping callback returned a correct virtual address of the passed PCI
config-space register. The problem of the proposed solution was that it
didn't take into account the way the host config-space is accessed on the
DW PCIe. Depending on the DW PCIe IP-core synthesize parameters different
interfaces can be used to access the host and peripheral config/memory
spaces. The former one can be accessed via the DBI interface, while the
later ones is reached via the AHB/AXI application bus. In case if the DW
PCIe controller is configured to have a dedicated DBI interface, the way
it is mapped into the IO-memory turns to be platform-specific. For such
setups the DWC PCIe driver provides a set of the callbacks
dw_pcie_ops.{read_dbi,write_dbi} so the platforms glue-drivers would be
able to take into account the DBI bus IO peculiarities. Since
commit c2b0c098fbd1 ("PCI: dwc: Use generic config accessors") these
methods haven't been utilized during the generic host initialization
performed by the PCIe subsystem code.

I don't really know how come there have been no problems spotted for the
Histb/Exynos/Kirin PCIe controllers so far, but in our case with dword
aligned IO requirement the generic config-space accessors can't be
utilized for the host config-space. Thus in order to make sure the host
config-space is properly accessed via the DBI bus let's get back the
dw_pcie_rd_own_conf() and dw_pcie_wr_own_conf() methods. They are going to
be just wrappers around the already defined
dw_pcie_read_dbi()/dw_pcie_write_dbi() functions with proper arguments
conversion. These methods perform the platform-specific config-space IO if
the DBI accessors are specified, otherwise they call normal MMIO
operations.

Fixes: c2b0c098fbd1 ("PCI: dwc: Use generic config accessors")
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 .../pci/controller/dwc/pcie-designware-host.c | 34 +++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 7403b1709726..a250869334a5 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -534,10 +534,40 @@ void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus, unsigned int devfn,
 }
 EXPORT_SYMBOL_GPL(dw_pcie_own_conf_map_bus);
 
+static int dw_pcie_rd_own_conf(struct pci_bus *bus, unsigned int devfn,
+			       int where, int size, u32 *val)
+{
+	struct pcie_port *pp = bus->sysdata;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+
+	if (PCI_SLOT(devfn) > 0) {
+		*val = ~0U;
+		return PCIBIOS_DEVICE_NOT_FOUND;
+	}
+
+	*val = dw_pcie_read_dbi(pci, where, size);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+
+static int dw_pcie_wr_own_conf(struct pci_bus *bus, unsigned int devfn,
+			       int where, int size, u32 val)
+{
+	struct pcie_port *pp = bus->sysdata;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+
+	if (PCI_SLOT(devfn) > 0)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	dw_pcie_write_dbi(pci, where, size, val);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+
 static struct pci_ops dw_pcie_ops = {
 	.map_bus = dw_pcie_own_conf_map_bus,
-	.read = pci_generic_config_read,
-	.write = pci_generic_config_write,
+	.read = dw_pcie_rd_own_conf,
+	.write = dw_pcie_wr_own_conf,
 };
 
 void dw_pcie_setup_rc(struct pcie_port *pp)
-- 
2.35.1