| Message ID | 20220226104731.76776-5-chenhuacai@loongson.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | PCI: Loongson pci improvements and quirks | expand |
On Sat, Feb 26, 2022 at 06:47:29PM +0800, Huacai Chen wrote: > In new revision of LS7A, some PCIe ports support larger value than 256, > but their maximum supported MRRS values are not detectable. Moreover, > the current loongson_mrrs_quirk() cannot avoid devices increasing its > MRRS after pci_enable_device(), and some devices (e.g. Realtek 8169) > will actually set a big value in its driver. So the only possible way > is configure MRRS of all devices in BIOS, and add a pci host bridge bit > flag (i.e., no_inc_mrrs) to stop the increasing MRRS operations. > > However, according to PCIe Spec, it is legal for an OS to program any > value for MRRS, and it is also legal for an endpoint to generate a Read > Request with any size up to its MRRS. As the hardware engineers say, the > root cause here is LS7A doesn't break up large read requests. In detail, > LS7A PCIe port reports CA (Completer Abort) if it receives a Memory Read > request with a size that's "too big" ("too big" means larger than the > PCIe ports can handle, which means 256 for some ports and 4096 for the > others, and of course this is a problem in the LS7A's hardware design). > > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> > --- > drivers/pci/controller/pci-loongson.c | 47 ++++++++++----------------- > drivers/pci/pci.c | 6 ++++ > include/linux/pci.h | 1 + > 3 files changed, 25 insertions(+), 29 deletions(-) > > diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c > index 48d9d283cb59..ba182f9d5718 100644 > --- a/drivers/pci/controller/pci-loongson.c > +++ b/drivers/pci/controller/pci-loongson.c > @@ -67,37 +67,26 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > DEV_LS7A_LPC, system_bus_quirk); > > -static void loongson_mrrs_quirk(struct pci_dev *dev) > +static void loongson_mrrs_quirk(struct pci_dev *pdev) > { > - struct pci_bus *bus = dev->bus; > - struct pci_dev *bridge; > - static const struct pci_device_id bridge_devids[] = { > - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_0) }, > - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_1) }, > - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_2) }, > - { 0, }, > - }; > - > - /* look for the matching bridge */ > - while (!pci_is_root_bus(bus)) { > - bridge = bus->self; > - bus = bus->parent; > - /* > - * Some Loongson PCIe ports have a h/w limitation of > - * 256 bytes maximum read request size. They can't handle > - * anything larger than this. So force this limit on > - * any devices attached under these ports. > - */ > - if (pci_match_id(bridge_devids, bridge)) { > - if (pcie_get_readrq(dev) > 256) { > - pci_info(dev, "limiting MRRS to 256\n"); > - pcie_set_readrq(dev, 256); > - } > - break; > - } > - } > + /* > + * Some Loongson PCIe ports have h/w limitations of maximum read > + * request size. They can't handle anything larger than this. So > + * force this limit on any devices attached under these ports. > + */ > + struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus); > + > + if (!bridge) Isn't this condition impossible? I'd drop and just let the NULL dereference fault happen rather than continue on silently. > + return; > + > + bridge->no_inc_mrrs = 1; > } > -DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, loongson_mrrs_quirk); > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > + DEV_PCIE_PORT_0, loongson_mrrs_quirk); > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > + DEV_PCIE_PORT_1, loongson_mrrs_quirk); > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > + DEV_PCIE_PORT_2, loongson_mrrs_quirk); > > static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus) > { > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 9ecce435fb3f..72a15bf9eee8 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -5993,6 +5993,7 @@ int pcie_set_readrq(struct pci_dev *dev, int rq) > { > u16 v; > int ret; > + struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus); > > if (rq < 128 || rq > 4096 || !is_power_of_2(rq)) > return -EINVAL; > @@ -6011,6 +6012,11 @@ int pcie_set_readrq(struct pci_dev *dev, int rq) > > v = (ffs(rq) - 8) << 12; > > + if (bridge->no_inc_mrrs) { > + if (rq > pcie_get_readrq(dev)) > + return -EINVAL; > + } > + > ret = pcie_capability_clear_and_set_word(dev, PCI_EXP_DEVCTL, > PCI_EXP_DEVCTL_READRQ, v); > > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 8253a5413d7c..01a464eb640a 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -569,6 +569,7 @@ struct pci_host_bridge { > void *release_data; > unsigned int ignore_reset_delay:1; /* For entire hierarchy */ > unsigned int no_ext_tags:1; /* No Extended Tags */ > + unsigned int no_inc_mrrs:1; /* No Increase MRRS */ > unsigned int native_aer:1; /* OS may use PCIe AER */ > unsigned int native_pcie_hotplug:1; /* OS may use PCIe hotplug */ > unsigned int native_shpc_hotplug:1; /* OS may use SHPC hotplug */ > -- > 2.27.0 >
Hi, Rob, On Tue, Apr 12, 2022 at 10:49 PM Rob Herring <robh@kernel.org> wrote: > > On Sat, Feb 26, 2022 at 06:47:29PM +0800, Huacai Chen wrote: > > In new revision of LS7A, some PCIe ports support larger value than 256, > > but their maximum supported MRRS values are not detectable. Moreover, > > the current loongson_mrrs_quirk() cannot avoid devices increasing its > > MRRS after pci_enable_device(), and some devices (e.g. Realtek 8169) > > will actually set a big value in its driver. So the only possible way > > is configure MRRS of all devices in BIOS, and add a pci host bridge bit > > flag (i.e., no_inc_mrrs) to stop the increasing MRRS operations. > > > > However, according to PCIe Spec, it is legal for an OS to program any > > value for MRRS, and it is also legal for an endpoint to generate a Read > > Request with any size up to its MRRS. As the hardware engineers say, the > > root cause here is LS7A doesn't break up large read requests. In detail, > > LS7A PCIe port reports CA (Completer Abort) if it receives a Memory Read > > request with a size that's "too big" ("too big" means larger than the > > PCIe ports can handle, which means 256 for some ports and 4096 for the > > others, and of course this is a problem in the LS7A's hardware design). > > > > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> > > --- > > drivers/pci/controller/pci-loongson.c | 47 ++++++++++----------------- > > drivers/pci/pci.c | 6 ++++ > > include/linux/pci.h | 1 + > > 3 files changed, 25 insertions(+), 29 deletions(-) > > > > diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c > > index 48d9d283cb59..ba182f9d5718 100644 > > --- a/drivers/pci/controller/pci-loongson.c > > +++ b/drivers/pci/controller/pci-loongson.c > > @@ -67,37 +67,26 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > > DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > > DEV_LS7A_LPC, system_bus_quirk); > > > > -static void loongson_mrrs_quirk(struct pci_dev *dev) > > +static void loongson_mrrs_quirk(struct pci_dev *pdev) > > { > > - struct pci_bus *bus = dev->bus; > > - struct pci_dev *bridge; > > - static const struct pci_device_id bridge_devids[] = { > > - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_0) }, > > - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_1) }, > > - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_2) }, > > - { 0, }, > > - }; > > - > > - /* look for the matching bridge */ > > - while (!pci_is_root_bus(bus)) { > > - bridge = bus->self; > > - bus = bus->parent; > > - /* > > - * Some Loongson PCIe ports have a h/w limitation of > > - * 256 bytes maximum read request size. They can't handle > > - * anything larger than this. So force this limit on > > - * any devices attached under these ports. > > - */ > > - if (pci_match_id(bridge_devids, bridge)) { > > - if (pcie_get_readrq(dev) > 256) { > > - pci_info(dev, "limiting MRRS to 256\n"); > > - pcie_set_readrq(dev, 256); > > - } > > - break; > > - } > > - } > > + /* > > + * Some Loongson PCIe ports have h/w limitations of maximum read > > + * request size. They can't handle anything larger than this. So > > + * force this limit on any devices attached under these ports. > > + */ > > + struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus); > > + > > + if (!bridge) > > Isn't this condition impossible? I'd drop and just let the NULL > dereference fault happen rather than continue on silently. This is copied from quirk_no_ext_tags(), and it seems can be removed, thanks. Huacai > > > + return; > > + > > + bridge->no_inc_mrrs = 1; > > } > > -DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, loongson_mrrs_quirk); > > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > > + DEV_PCIE_PORT_0, loongson_mrrs_quirk); > > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > > + DEV_PCIE_PORT_1, loongson_mrrs_quirk); > > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, > > + DEV_PCIE_PORT_2, loongson_mrrs_quirk); > > > > static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus) > > { > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > > index 9ecce435fb3f..72a15bf9eee8 100644 > > --- a/drivers/pci/pci.c > > +++ b/drivers/pci/pci.c > > @@ -5993,6 +5993,7 @@ int pcie_set_readrq(struct pci_dev *dev, int rq) > > { > > u16 v; > > int ret; > > + struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus); > > > > if (rq < 128 || rq > 4096 || !is_power_of_2(rq)) > > return -EINVAL; > > @@ -6011,6 +6012,11 @@ int pcie_set_readrq(struct pci_dev *dev, int rq) > > > > v = (ffs(rq) - 8) << 12; > > > > + if (bridge->no_inc_mrrs) { > > + if (rq > pcie_get_readrq(dev)) > > + return -EINVAL; > > + } > > + > > ret = pcie_capability_clear_and_set_word(dev, PCI_EXP_DEVCTL, > > PCI_EXP_DEVCTL_READRQ, v); > > > > diff --git a/include/linux/pci.h b/include/linux/pci.h > > index 8253a5413d7c..01a464eb640a 100644 > > --- a/include/linux/pci.h > > +++ b/include/linux/pci.h > > @@ -569,6 +569,7 @@ struct pci_host_bridge { > > void *release_data; > > unsigned int ignore_reset_delay:1; /* For entire hierarchy */ > > unsigned int no_ext_tags:1; /* No Extended Tags */ > > + unsigned int no_inc_mrrs:1; /* No Increase MRRS */ > > unsigned int native_aer:1; /* OS may use PCIe AER */ > > unsigned int native_pcie_hotplug:1; /* OS may use PCIe hotplug */ > > unsigned int native_shpc_hotplug:1; /* OS may use SHPC hotplug */ > > -- > > 2.27.0 > >
diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c index 48d9d283cb59..ba182f9d5718 100644 --- a/drivers/pci/controller/pci-loongson.c +++ b/drivers/pci/controller/pci-loongson.c @@ -67,37 +67,26 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, DEV_LS7A_LPC, system_bus_quirk); -static void loongson_mrrs_quirk(struct pci_dev *dev) +static void loongson_mrrs_quirk(struct pci_dev *pdev) { - struct pci_bus *bus = dev->bus; - struct pci_dev *bridge; - static const struct pci_device_id bridge_devids[] = { - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_0) }, - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_1) }, - { PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_2) }, - { 0, }, - }; - - /* look for the matching bridge */ - while (!pci_is_root_bus(bus)) { - bridge = bus->self; - bus = bus->parent; - /* - * Some Loongson PCIe ports have a h/w limitation of - * 256 bytes maximum read request size. They can't handle - * anything larger than this. So force this limit on - * any devices attached under these ports. - */ - if (pci_match_id(bridge_devids, bridge)) { - if (pcie_get_readrq(dev) > 256) { - pci_info(dev, "limiting MRRS to 256\n"); - pcie_set_readrq(dev, 256); - } - break; - } - } + /* + * Some Loongson PCIe ports have h/w limitations of maximum read + * request size. They can't handle anything larger than this. So + * force this limit on any devices attached under these ports. + */ + struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus); + + if (!bridge) + return; + + bridge->no_inc_mrrs = 1; } -DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, loongson_mrrs_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, + DEV_PCIE_PORT_0, loongson_mrrs_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, + DEV_PCIE_PORT_1, loongson_mrrs_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON, + DEV_PCIE_PORT_2, loongson_mrrs_quirk); static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus) { diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 9ecce435fb3f..72a15bf9eee8 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5993,6 +5993,7 @@ int pcie_set_readrq(struct pci_dev *dev, int rq) { u16 v; int ret; + struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus); if (rq < 128 || rq > 4096 || !is_power_of_2(rq)) return -EINVAL; @@ -6011,6 +6012,11 @@ int pcie_set_readrq(struct pci_dev *dev, int rq) v = (ffs(rq) - 8) << 12; + if (bridge->no_inc_mrrs) { + if (rq > pcie_get_readrq(dev)) + return -EINVAL; + } + ret = pcie_capability_clear_and_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_DEVCTL_READRQ, v); diff --git a/include/linux/pci.h b/include/linux/pci.h index 8253a5413d7c..01a464eb640a 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -569,6 +569,7 @@ struct pci_host_bridge { void *release_data; unsigned int ignore_reset_delay:1; /* For entire hierarchy */ unsigned int no_ext_tags:1; /* No Extended Tags */ + unsigned int no_inc_mrrs:1; /* No Increase MRRS */ unsigned int native_aer:1; /* OS may use PCIe AER */ unsigned int native_pcie_hotplug:1; /* OS may use PCIe hotplug */ unsigned int native_shpc_hotplug:1; /* OS may use SHPC hotplug */
In new revision of LS7A, some PCIe ports support larger value than 256, but their maximum supported MRRS values are not detectable. Moreover, the current loongson_mrrs_quirk() cannot avoid devices increasing its MRRS after pci_enable_device(), and some devices (e.g. Realtek 8169) will actually set a big value in its driver. So the only possible way is configure MRRS of all devices in BIOS, and add a pci host bridge bit flag (i.e., no_inc_mrrs) to stop the increasing MRRS operations. However, according to PCIe Spec, it is legal for an OS to program any value for MRRS, and it is also legal for an endpoint to generate a Read Request with any size up to its MRRS. As the hardware engineers say, the root cause here is LS7A doesn't break up large read requests. In detail, LS7A PCIe port reports CA (Completer Abort) if it receives a Memory Read request with a size that's "too big" ("too big" means larger than the PCIe ports can handle, which means 256 for some ports and 4096 for the others, and of course this is a problem in the LS7A's hardware design). Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> --- drivers/pci/controller/pci-loongson.c | 47 ++++++++++----------------- drivers/pci/pci.c | 6 ++++ include/linux/pci.h | 1 + 3 files changed, 25 insertions(+), 29 deletions(-)