[U-Boot] [PATCH 1/1] pci: pci_mvebu: ignore the local device

[Marek Behún]

The local device (host "bridge"?) on pci_mvebu controller reports
PCI_CLASS_MEMORY_OTHER in the class register.

This does not work in U-Boot, because U-Boot then tries to autoconfigure
this device in pci_auto.c. This causes the real connected PCIe device
not to work (in U-Boot nor in Linux).

Linux solves this by emulating PCI bridge device (see
drivers/pci/pci-bridge-emul.c in Linux). The Marvell vendor/device IDs
are used for this pci-bridge-emul device in Linux, but the actual
register accesses are emulated and the value of class register is
PCI_CLASS_BRIDGE_PCI.

The simplest solution here in my opinion is to just ignore the local
device in this driver's read/write methods. This fixes PCIe issues for
me.

Signed-off-by: Marek Behún <marek.behun at nic.cz>
Cc: Stefan Roese <sr at denx.de>
Cc: Anton Schubert <anton.schubert at gmx.de>
Cc: Dirk Eibach <dirk.eibach at gdsys.cc>
Cc: Mario Six <mario.six at gdsys.cc>
Cc: Chris Packham <chris.packham at alliedtelesis.co.nz>
Cc: Phil Sutter <phil at nwl.cc>
Cc: VlaoMao <vlaomao at gmail.com>
---
 drivers/pci/pci_mvebu.c | 59 +++++++++++++++++------------------------
 1 file changed, 24 insertions(+), 35 deletions(-)

diff --git a/drivers/pci/pci_mvebu.c b/drivers/pci/pci_mvebu.c
index e21dc10c2f..653f445a0f 100644
--- a/drivers/pci/pci_mvebu.c
+++ b/drivers/pci/pci_mvebu.c
@@ -143,31 +143,31 @@ static int mvebu_pcie_read_config(struct udevice *bus, pci_dev_t bdf,
 	struct mvebu_pcie *pcie = dev_get_platdata(bus);
 	int local_bus = PCI_BUS(pcie->dev);
 	int local_dev = PCI_DEV(pcie->dev);
+	int other_dev;
 	u32 reg;
 	u32 data;
 
 	debug("PCIE CFG read:  (b,d,f)=(%2d,%2d,%2d) ",
 	      PCI_BUS(bdf), PCI_DEV(bdf), PCI_FUNC(bdf));
 
-	/* Only allow one other device besides the local one on the local bus */
-	if (PCI_BUS(bdf) == local_bus && PCI_DEV(bdf) != local_dev) {
-		if (local_dev == 0 && PCI_DEV(bdf) != 1) {
-			debug("- out of range\n");
-			/*
-			 * If local dev is 0, the first other dev can
-			 * only be 1
-			 */
-			*valuep = pci_get_ff(size);
-			return 0;
-		} else if (local_dev != 0 && PCI_DEV(bdf) != 0) {
-			debug("- out of range\n");
-			/*
-			 * If local dev is not 0, the first other dev can
-			 * only be 0
-			 */
-			*valuep = pci_get_ff(size);
-			return 0;
-		}
+	/*
+	 * The local device has PCI_CLASS_MEMORY_OTHER in the class register.
+	 * This does not work for U-Boot because pci_auto.c tries to configure
+	 * this as a device. This results in U-Boot/Linux being unable to access
+	 * PCIe devices.
+	 *
+	 * Linux solves this by emulating a bridge (see
+	 * drivers/pci/pci-bridge-emul.c in Linux).
+	 *
+	 * Let's ignore the local device in U-Boot.
+	 *
+	 * Also only allow one other device besides the (ignored) local one.
+	 */
+
+	other_dev = local_dev ? 0 : 1;
+	if (PCI_BUS(bdf) == local_bus && PCI_DEV(bdf) != other_dev) {
+		*valuep = pci_get_ff(size);
+		return 0;
 	}
 
 	/* write address */
@@ -187,28 +187,17 @@ static int mvebu_pcie_write_config(struct udevice *bus, pci_dev_t bdf,
 	struct mvebu_pcie *pcie = dev_get_platdata(bus);
 	int local_bus = PCI_BUS(pcie->dev);
 	int local_dev = PCI_DEV(pcie->dev);
+	int other_dev;
 	u32 data;
 
 	debug("PCIE CFG write: (b,d,f)=(%2d,%2d,%2d) ",
 	      PCI_BUS(bdf), PCI_DEV(bdf), PCI_FUNC(bdf));
 	debug("(addr,val)=(0x%04x, 0x%08lx)\n", offset, value);
 
-	/* Only allow one other device besides the local one on the local bus */
-	if (PCI_BUS(bdf) == local_bus && PCI_DEV(bdf) != local_dev) {
-		if (local_dev == 0 && PCI_DEV(bdf) != 1) {
-			/*
-			 * If local dev is 0, the first other dev can
-			 * only be 1
-			 */
-			return 0;
-		} else if (local_dev != 0 && PCI_DEV(bdf) != 0) {
-			/*
-			 * If local dev is not 0, the first other dev can
-			 * only be 0
-			 */
-			return 0;
-		}
-	}
+	/* See the comment in mvebu_pcie_read_config */
+	other_dev = local_dev ? 0 : 1;
+	if (PCI_BUS(bdf) == local_bus && PCI_DEV(bdf) != other_dev)
+		return 0;
 
 	writel(PCIE_CONF_ADDR(bdf, offset), pcie->base + PCIE_CONF_ADDR_OFF);
 	data = pci_conv_size_to_32(0, value, offset, size);
-- 
2.21.0