DWC PCIe controller imposes limits on the Read Request Size that it can
handle. For i.MX6 family it's fixed at 512 bytes by default.
If a memory read larger than the limit is requested, the CPU responds
with Completer Abort (CA) (on i.MX6 Unsupported Request (UR) is returned
instead due to a design error).
The i.MX6 documentation states that the limit can be changed by writing
to the PCIE_PL_MRCCR0 register, however there is a fixed (and
undocumented) maximum (CX_REMOTE_RD_REQ_SIZE constant). Tests indicate
that values larger than 512 bytes don't work, though.
This patch makes the RTL8111 work on i.MX6.
Signed-off-by: Krzysztof Hałasa <khalasa@xxxxxxx>
---
This version drops CONFIG_NEED_PCIE_MAX_MRRS.
diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 80fc98acf097..225380e75fff 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -1148,6 +1148,7 @@ static int imx6_pcie_probe(struct platform_device *pdev)
imx6_pcie->vph = NULL;
}
+ max_pcie_mrrs = 512;
platform_set_drvdata(pdev, imx6_pcie);
ret = imx6_pcie_attach_pd(dev);
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index aacf575c15cf..44815af4ad85 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -112,6 +112,10 @@ enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_PEER2PEER;
enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_DEFAULT;
#endif
+#ifdef CONFIG_ARM
+u16 max_pcie_mrrs = 4096; // no limit - needed mostly for DWC PCIe
+#endif
+
/*
* The default CLS is used if arch didn't set CLS explicitly and not
* all pci devices agree on the same value. Arch can override either
@@ -5816,6 +5820,11 @@ int pcie_set_readrq(struct pci_dev *dev, int rq)
rq = mps;
}
+#ifdef CONFIG_ARM
+ if (rq > max_pcie_mrrs)
+ rq = max_pcie_mrrs;
+#endif
+
v = (ffs(rq) - 8) << 12;
ret = pcie_capability_clear_and_set_word(dev, PCI_EXP_DEVCTL,
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 06ff1186c1ef..1f21ec662b8e 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -996,6 +996,7 @@ enum pcie_bus_config_types {
};
extern enum pcie_bus_config_types pcie_bus_config;
+extern u16 max_pcie_mrrs; // currently ARM only
extern struct bus_type pci_bus_type;
--
Krzysztof "Chris" Hałasa
Sieć Badawcza Łukasiewicz
Przemysłowy Instytut Automatyki i Pomiarów PIAP
Al. Jerozolimskie 202, 02-486 Warszawa
