[PATCH 10/15] PCI: mvebu: Set PCI Bridge Class Code to PCI Bridge

Pali Rohár
2021-11-25T12:50:10Z

The default value of Class Code of this bridge corresponds to a Memory
controller, though. This is probably relict from the past when old
Marvell/Galileo PCI-based controllers were used as standalone PCI device
for connecting SDRAM or workaround for PCs with broken BIOS. Details are
in commit 36de23a4c5f0 ("MIPS: Cobalt: Explain GT64111 early PCI fixup").

Change the Class Code to correspond to a PCI Bridge.

Add comment explaining this change.

Signed-off-by: Pali Rohár <pali@kernel.org>
Cc: stable@vger.kernel.org
---
drivers/pci/controller/pci-mvebu.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
index 017ae9f869ac..4edce441901c 100644
--- a/drivers/pci/controller/pci-mvebu.c
+++ b/drivers/pci/controller/pci-mvebu.c
@@ -225,7 +225,7 @@ static void mvebu_pcie_setup_wins(struct mvebu_pcie_port *port)

static void mvebu_pcie_setup_hw(struct mvebu_pcie_port *port)
{
- u32 ctrl, cmd, mask;
+ u32 ctrl, cmd, dev_rev, mask;

/* Setup PCIe controller to Root Complex mode. */
ctrl = mvebu_readl(port, PCIE_CTRL_OFF);
@@ -237,6 +237,32 @@ static void mvebu_pcie_setup_hw(struct mvebu_pcie_port *port)
cmd &= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY | PCI_COMMAND_MASTER);
mvebu_writel(port, cmd, PCIE_CMD_OFF);

+ /*
+ * Change Class Code of PCI Bridge device to PCI Bridge (0x6004)
+ * because default value is Memory controller (0x5080).
+ *
+ * Note that this mvebu PCI Bridge does not have compliant Type 1
+ * Configuration Space. Header Type is reported as Type 0 and it
+ * has format of Type 0 config space.
+ *
+ * Moreover Type 0 BAR registers (ranges 0x10 - 0x28 and 0x30 - 0x34)
+ * have the same format in Marvell's specification as in PCIe
+ * specification, but their meaning is totally different and they do
+ * different things: they are aliased into internal mvebu registers
+ * (e.g. PCIE_BAR_LO_OFF) and these should not be changed or
+ * reconfigured by pci device drivers.
+ *
+ * Therefore driver uses emulation of PCI Bridge which emulates
+ * access to configuration space via internal mvebu registers or
+ * emulated configuration buffer. Driver access these PCI Bridge
+ * directly for simplification, but these registers can be accessed
+ * also via standard mvebu way for accessing PCI config space.
+ */
+ dev_rev = mvebu_readl(port, PCIE_DEV_REV_OFF);
+ dev_rev &= ~0xffffff00;
+ dev_rev |= (PCI_CLASS_BRIDGE_PCI << 8) << 8;
+ mvebu_writel(port, dev_rev, PCIE_DEV_REV_OFF);
+
/* Point PCIe unit MBUS decode windows to DRAM space. */
mvebu_pcie_setup_wins(port);

--
2.20.1