Hi, Huacai and Bjorn,
Actually, I don't think we have to fix the MRRS issue of 7A in this
way(change core code of PCI). The reasons are:
- First, we don't know if other pci controlers have simillar issue, at
least I don't see yet. I think if *only we* have the issue, maybe we can
fix it in our controller driver rather than changing core code. And in
future, if the issue is proved a common one, abstract it then by common way.
- Second, even though we limit the MRRS in pcie_set_readrq() according
to the flag set in quirk function, some drivers(e.g. in
drivers/rapidio/devices/tsi721.c, maybe other driver do this in future,
I dont't know.) directly call pcie_capability_clear_and_set_word to set
MRRS, which will still break the fix.
- Third, on resuming from S3, the MRRS stored in memory should be
allowed to set to dev ctrl reg(because the reg has been reset during S3).
Fix MMRS in our controller driver by using self-defined config_write(),
maybe like this:
static u32 handle_mrrs_limit(struct pci_bus *bus, unsigned int devfn,
void __iomem *addr, u32 val)
{
u32 tmp;
bool runtime_flag = 1;
int pos = pci_bus_find_capability_nolock(bus, devfn, PCI_CAP_ID_EXP);
#ifdef CONFIG_PM_SLEEP
if (pm_suspend_target_state == PM_SUSPEND_ON)
runtime_flag = 0;
#endif
if (resume_flag && pos != 0 && (pos + PCI_EXP_DEVCTL) == reg) {
tmp = readl(addr);
if ((val & PCI_EXP_DEVCTL_READRQ) > (tmp &
PCI_EXP_DEVCTL_READRQ)) {
val &= ~PCI_EXP_DEVCTL_READRQ;
val |= (tmp & PCI_EXP_DEVCTL_READRQ);
}
}
return val;
}
static int loongson_pci_config_write32(struct pci_bus *bus, unsigned int
devfn,
int where, int size, u32 val)
{
void __iomem *addr;
u32 mask, tmp;
int reg = where & ~3;
addr = bus->ops->map_bus(bus, devfn, where & ~0x3);
if (!addr)
return PCIBIOS_DEVICE_NOT_FOUND;
val = handle_mrrs_limit(bus, devfn, addr, reg, val);
writel(val, addr);
return PCIBIOS_SUCCESSFUL;
}
And I still have to emphasize on the fix in this way: It's still does
not work for pciehp. It's only used for addressing MRRS issue of 7A
revisions which have no pciehp support.
And in future, for new revision, we just need to skip handle_mrrs_limit.
The way described here is just my immature opinion, we can discuss it
if required.
Thanks.
On 2022/7/14 下午8:42, 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@xxxxxxxxxxx>
---
drivers/pci/controller/pci-loongson.c | 44 +++++++++------------------
drivers/pci/pci.c | 6 ++++
include/linux/pci.h | 1 +
3 files changed, 22 insertions(+), 29 deletions(-)
diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index 594653154deb..af73bb766e48 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -68,37 +68,23 @@ 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);
+
+ 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 cfaf40a540a8..79157cbad835 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6052,6 +6052,7 @@ 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;
@@ -6070,6 +6071,11 @@ 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 81a57b498f22..a9211074add6 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 */
