| Message ID | m37fdydikf.fsf@t19.piap.pl (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Thursday, June 9, 2016 7:42:24 AM CEST Krzysztof Hałasa wrote: > Arnd Bergmann <arnd@arndb.de> writes: > > > What exactly is the problem we are seeing, and is there a way to fix > > it on top of my patch? Are we perhaps just missing a call to > > pcie_bus_configure_settings()? > > From: khalasa@piap.pl (Krzysztof Halasa) > Subject: [PATCH] Extend PCIE_BUS_PEER2PEER to set MRSS=128 to fix CNS3xxx BM DMA. > To: Bjorn Helgaas <bhelgaas@google.com> > Cc: Arnd Bergmann <arnd@arndb.de>, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org > Date: Mon, 21 Mar 2016 10:39:52 +0100 (11 weeks, 2 days, 19 hours ago) > > The platform in question is Cavium CNS3xxx, ARMv6. > > A recent patch by Arnd Bergmann (498a92d42596 "ARM: cns3xxx: pci: avoid > potential stack overflow") converted an explicit setting of > PCI_EXP_DEVCTL_READRQ = 0 (i.e., max 128 bytes for bus-mastering PCIe DMA > read request) to: > + pcie_bus_config = PCIE_BUS_PEER2PEER; > > with the following commentary: > "The second part is how the driver sets up the Max_Read_Request_Size > value for the first device/function on bus 1, i.e. the device > plugged directly into the PCIe root port. > For all I can tell, this is in fact incomplete, as it does not > perform the same setting on devices attached to a PCIe switch, > or multi-function devices. > The solution for this part fortunately is even easier: if we > just set the global pcie_bus_config variable to PCIE_BUS_PEER2PEER, > all PCIe devices in the system are limited to 128 byte MPS, which > in turn limits the MRRS to 128 bytes for all devices, and we > no longer even need to touch any devices." > > The problem is the MRRS setting is never written to the hardware. > I propose the following, though I'm not sure if we can do this safely, > especially given the comments in probe.c. OTOH, this change may be > required in other (all?) cases when the user requests > PCIE_BUS_PEER2PEER. > > On this Laguna GW-2388 the following patch fixes BM DMA with: > 0000:00:00.0 PCI bridge: Cavium Networks Device 3400 (rev 01) > 0000:01:00.0 PCI bridge: Texas Instruments XIO2001 PCI Express-to-PCI Bridge > 0000:02:0e.0 (PCI devices behind the bridge, these are doing actual BM xfers) > 0001:00:00.0 PCI bridge: Cavium Networks Device 3400 (rev 01 - this is > the second lane from the CPU) > > pci 0000:00:00.0: Max Payload Size set to 128/ 128 (was 128), Max Read Rq 128 > pci 0000:01:00.0: Max Payload Size set to 128/ 512 (was 128), Max Read Rq 128 > pci 0001:00:00.0: Max Payload Size set to 128/ 128 (was 128), Max Read Rq 128 > > Signed-off-by: Krzysztof Hałasa <khalasa@piap.pl> > Fixes: 498a92d42596 ("ARM: cns3xxx: pci: avoid potential stack overflow") I see now, thanks for the quote. I guess I missed how PCIE_BUS_PEER2PEER is documented as /* set MPS = 128 for all devices */ unlike PCIE_BUS_PERFORMANCE, which is documented as setting both MPS and MRRS. It seems the current behavior was introduced by http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ed2888e90 Before that, we were always setting both mrrs and mps. As we don't know who uses PCIE_BUS_PEER2PEER, maybe another option would be to add yet another pcie_bus_config value for this particular quirk? > > Note that cns3xxx is in a bit of an odd state, as only half of the > > platform code is even present in the kernel, and there is no effort > > to change that. As far as I know, the board that this was tested on > > is not present in the mainline kernel, and the board we support > > is a development system that few people even own at this point. > > The boards I use (Gateworks Laguna) are basically equivalent to the > devel board (from the platform code POV). > The kernel lacks support for SMP and the Ethernet driver (and things > like GPIO), though there are patches available and I plan to integrate > them, when the existing issues are resolved. Ok, good to know. > Also, this is practically a non-DT arch but I guess a conversion to DT > would be a good thing as it would eliminate a need for board-specific > code. That's why there is no platform code for Laguna. Unfortunately > there is no DT file for CNS3xxx, and I'm not an DT expert. I started the DT conversion a long time ago (see the DT parsing in arch/arm/mach-cns3xxx/core.c) but I never had any hardware to test on, and it was at a time when we didn't even have DT support in all the subsystems. I'd definitely help you get the rest of the DT support in place if you can test it. This is now the only SMP platform and one of the last users of GIC and l2x0 that does not use DT, so I'd love to see that converted just so we can remove the legacy probing from those drivers. Converting what we have in mainline should be fairly straightforward, but there is more code in target/linux/cns3xxx/files/arch/arm/mach-cns3xxx/laguna.c that requires more work, in particular we need to come up with a way to handle the laguna_net_data and laguna_info structures, which have some of the same data that is normall in DT. Also, the gpio driver doesn't have a trivial conversion to DT and requires some work to define a binding and implement that. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Arnd Bergmann <arnd@arndb.de> writes: > Before that, we were always setting both mrrs and mps. As we don't know > who uses PCIE_BUS_PEER2PEER, maybe another option would be to add yet > another pcie_bus_config value for this particular quirk? It would be a safe approach. Or, maybe another non-pcie_bus_config thing, I don't know (so the pcie_bus_config is left for the user). > I started the DT conversion a long time ago (see the DT parsing in > arch/arm/mach-cns3xxx/core.c) but I never had any hardware to test > on, and it was at a time when we didn't even have DT support in all > the subsystems. > > I'd definitely help you get the rest of the DT support in place if > you can test it. This is now the only SMP platform and one of > the last users of GIC and l2x0 that does not use DT, so I'd love > to see that converted just so we can remove the legacy probing from > those drivers. Ok. Is there a DT skeleton file somewhere, so I can try to boot the board (without Laguna extras) in DT mode? At first, I only need CPU + RAM + console serial port. > Converting what we have in mainline should be fairly straightforward, > but there is more code in > target/linux/cns3xxx/files/arch/arm/mach-cns3xxx/laguna.c that requires > more work, in particular we need to come up with a way to handle > the laguna_net_data and laguna_info structures, which have some of > the same data that is normall in DT. I assume adding this to U-Boot should be acceptable (for Gateworks, too). They are already doing this to their i.MX6 line Ventana. > Also, the gpio driver doesn't > have a trivial conversion to DT and requires some work to define > a binding and implement that. GPIO is a bit less important ATM, since the boards can boot without it.
On Friday, June 10, 2016 12:10:14 PM CEST Krzysztof Hałasa wrote: > Arnd Bergmann <arnd@arndb.de> writes: > > > Before that, we were always setting both mrrs and mps. As we don't know > > who uses PCIE_BUS_PEER2PEER, maybe another option would be to add yet > > another pcie_bus_config value for this particular quirk? > > It would be a safe approach. > Or, maybe another non-pcie_bus_config thing, I don't know (so > the pcie_bus_config is left for the user). > > > I started the DT conversion a long time ago (see the DT parsing in > > arch/arm/mach-cns3xxx/core.c) but I never had any hardware to test > > on, and it was at a time when we didn't even have DT support in all > > the subsystems. > > > > I'd definitely help you get the rest of the DT support in place if > > you can test it. This is now the only SMP platform and one of > > the last users of GIC and l2x0 that does not use DT, so I'd love > > to see that converted just so we can remove the legacy probing from > > those drivers. > > Ok. Is there a DT skeleton file somewhere, so I can try to boot the > board (without Laguna extras) in DT mode? > At first, I only need CPU + RAM + console serial port. I'd start by copying the relevant nodes from arch/arm/boot/dts/arm-realview-pb11mp.dts, which is the closest I can think of. I've put together something completely untested below. The key part is to have the correct "compatible" property in the root node, which must list the actual machine before listing "cavium,cns3420" to match the machine descriptor in arch/arm/mach-cns3xxx/core.c The RAM will be filled from the atags compatibility code (but it makes sense to list it anyway), and the serial port is not even needed in the first iteration if you heave CONFIG_DEBUG_CNS3XXX set. > > Converting what we have in mainline should be fairly straightforward, > > but there is more code in > > target/linux/cns3xxx/files/arch/arm/mach-cns3xxx/laguna.c that requires > > more work, in particular we need to come up with a way to handle > > the laguna_net_data and laguna_info structures, which have some of > > the same data that is normall in DT. > > I assume adding this to U-Boot should be acceptable (for Gateworks, > too). They are already doing this to their i.MX6 line Ventana. Ok, if U-Boot can convert the configuration into the right DT properties, that is ideal. > > Also, the gpio driver doesn't > > have a trivial conversion to DT and requires some work to define > > a binding and implement that. > > GPIO is a bit less important ATM, since the boards can boot without it. Ok. Arnd --- /dts-v1/; #include <dt-bindings/interrupt-controller/irq.h> #include <dt-bindings/gpio/gpio.h> #include "skeleton.dtsi" / { model = "Cavium CNS3420 validation board"; compatible = "cavium,cns3420"; interrupt-parent = <&gic>; chosen { }; aliases { serial0 = &serial; }; memory { /* 256MB at address 0 */ reg = <0x00000000 0x10000000>; }; cpus { #address-cells = <1>; #size-cells = <0>; enable-method = "cavium,cns3420-smp"; cpu@0 { device_type = "cpu"; compatible = "arm,arm11mpcore"; reg = <0>; next-level-cache = <&L2>; }; cpu@1 { device_type = "cpu"; compatible = "arm,arm11mpcore"; reg = <1>; next-level-cache = <&L2>; }; }; /* Primary TestChip GIC synthesized with the CPU */ gic: interrupt-controller@1f000100 { compatible = "arm,arm11mp-gic"; #interrupt-cells = <3>; #address-cells = <1>; interrupt-controller; reg = <0x90001000 0x1000>, <0x90000100 0x100>; }; L2: l2-cache { compatible = "arm,l220-cache"; reg = <0x92002000 0x1000>; interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>; cache-unified; cache-level = <2>; /* all of the below are probably wrong and have to be fixed before we can use l2x0_of_init */ cache-size = <1048576>; // 1MB cache-sets = <4096>; cache-line-size = <32>; arm,shared-override; arm,parity-enable; arm,outer-sync-disable; }; scu@1f000000 { compatible = "arm,arm11mp-scu"; reg = <0x90000000 0x100>; }; flash@10000000 { /* 128MiB NOR Flash memory */ compatible = "cfi-flash"; reg = <0x10000000 0x08000000>; bank-width = <2>; partition@00000000 { label = "uboot"; reg = <0 0x00040000>; }; partition@00040000 { label = "kernel"; reg = <0x00040000 0x004c0000>; }; partition@00500000 { label = "filesystem"; reg = <0x00500000 0x07000000>; }; partition@07500000 { label = "filesystem2"; reg = <0x07500000 0x00ae0000>; }; partition@07fe0000 { label = "ubootenv"; reg = <0x07fe0000 0x00020000>; }; }; soc { #address-cells = <1>; #size-cells = <1>; compatible = "simple-bus"; ranges; serial0: serial@78000000 { compatible = "ns16550a"; reg = <0x78000000 0x1000>; interrupts = <GIC_SPI 13 IRQ_TYPE_LEVEL_HIGH>; regshift = <2>; clocks = <&uartclk>; }; }; }; -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Arnd Bergmann <arnd@arndb.de> writes: > I'd start by copying the relevant nodes from > arch/arm/boot/dts/arm-realview-pb11mp.dts, which is the closest > I can think of. I've put together something completely untested > below. Thanks. I will try to handle that. 3+ weeks, unfortunately. Now, what do we do with the PCIe MRRS?
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 6d7ab9b..91713b6 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1919,7 +1919,8 @@ static void pcie_write_mrrs(struct pci_dev *dev) /* In the "safe" case, do not configure the MRRS. There appear to be * issues with setting MRRS to 0 on a number of devices. */ - if (pcie_bus_config != PCIE_BUS_PERFORMANCE) + if (pcie_bus_config != PCIE_BUS_PERFORMANCE && + pcie_bus_config != PCIE_BUS_PEER2PEER) return; /* For Max performance, the MRRS must be set to the largest supported diff --git a/include/linux/pci.h b/include/linux/pci.h index 2771625..6f5088a 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -756,7 +756,7 @@ enum pcie_bus_config_types { PCIE_BUS_DEFAULT, /* ensure MPS matches upstream bridge */ PCIE_BUS_SAFE, /* use largest MPS boot-time devices support */ PCIE_BUS_PERFORMANCE, /* use MPS and MRRS for best performance */ - PCIE_BUS_PEER2PEER, /* set MPS = 128 for all devices */ + PCIE_BUS_PEER2PEER, /* set MPS and MRSS to 128 for all devices */ }; extern enum pcie_bus_config_types pcie_bus_config;