On Tue, Oct 30, 2018 at 12:36:08PM -0400, Mikulas Patocka wrote:
> The macros PCI_EXP_LNKCAP_SLS_*GB are values, not bit masks. We must mask
> the register and compare it against them.
>
> This patch fixes errors "amdgpu: [powerplay] failed to send message 261
> ret is 0" errors when PCIe-v3 card is plugged into PCIe-v1 slot, because
> the slot is being incorrectly reported as PCIe-v3 capable.
>
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Fixes: 6cf57be0f78e ("PCI: Add pcie_get_speed_cap() to find max supported link speed")
> Cc: stable@xxxxxxxxxxxxxxx # v4.17+
>
> ---
> drivers/pci/pci.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> Index: linux-4.19/drivers/pci/pci.c
> ===================================================================
> --- linux-4.19.orig/drivers/pci/pci.c 2018-10-30 16:58:58.000000000 +0100
> +++ linux-4.19/drivers/pci/pci.c 2018-10-30 16:58:58.000000000 +0100
> @@ -5492,13 +5492,13 @@ enum pci_bus_speed pcie_get_speed_cap(st
>
> pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
> if (lnkcap) {
> - if (lnkcap & PCI_EXP_LNKCAP_SLS_16_0GB)
> + if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_16_0GB)
> return PCIE_SPEED_16_0GT;
> - else if (lnkcap & PCI_EXP_LNKCAP_SLS_8_0GB)
> + else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_8_0GB)
> return PCIE_SPEED_8_0GT;
> - else if (lnkcap & PCI_EXP_LNKCAP_SLS_5_0GB)
> + else if ((lnkcap & PCI_EXP_LNKCAP_SLS) ==PCI_EXP_LNKCAP_SLS_5_0GB)
> return PCIE_SPEED_5_0GT;
> - else if (lnkcap & PCI_EXP_LNKCAP_SLS_2_5GB)
> + else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_2_5GB)
> return PCIE_SPEED_2_5GT;
> }
>
I'd like to apply this as below, where I removed the 8_0GB and 16_0GB
cases as recommended by the spec. I can't test it myself, and the
bugzillas don't contain enough information for me to confirm that the
patch below is enough (the "lspci -vv" output of the root port and GPU
is what I would need).
I'm confused about the fact that 6cf57be0f78e appeared in v4.17, but
v4.18 works fine according to both bugzillas.
I also don't have a good feel for whether this is urgent enough to be
a v4.20 fix or whether it can wait for v4.21. Evidence either way
would help.
We also need similar fixes in pci_set_bus_speed(), pcie_speeds()
(hfi1), cobalt_pcie_status_show(), hba_ioctl_callback(),
qla24xx_pci_info_str(), and maybe a couple other places.
Bjorn
commit 871f73abf4b8e6aee8a206775f944ede7c7d7250
Author: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date: Tue Oct 30 12:36:08 2018 -0400
PCI: Fix incorrect value returned from pcie_get_speed_cap()
The macros PCI_EXP_LNKCAP_SLS_*GB are values, not bit masks. We must mask
the register and compare it against them.
This patch fixes errors "amdgpu: [powerplay] failed to send message 261 ret
is 0" errors when PCIe-v3 card is plugged into PCIe-v1 slot, because the
slot is being incorrectly reported as PCIe-v3 capable.
Fixes: 6cf57be0f78e ("PCI: Add pcie_get_speed_cap() to find max supported link speed")
Link: https://bugs.freedesktop.org/show_bug.cgi?id=108704
Link: https://bugs.freedesktop.org/show_bug.cgi?id=108778
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
[bhelgaas: update comment, remove use of PCI_EXP_LNKCAP_SLS_8_0GB and
PCI_EXP_LNKCAP_SLS_16_0GB since those should be covered by PCI_EXP_LNKCAP2]
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.17+
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d068f11d08a7..8563d1d9b102 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5556,9 +5556,13 @@ enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev)
u32 lnkcap2, lnkcap;
/*
- * PCIe r4.0 sec 7.5.3.18 recommends using the Supported Link
- * Speeds Vector in Link Capabilities 2 when supported, falling
- * back to Max Link Speed in Link Capabilities otherwise.
+ * Link Capabilities 2 was added in PCIe r3.0, sec 7.8.18. The
+ * implementation note there recommends using the Supported Link
+ * Speeds Vector in Link Capabilities 2 when supported.
+ *
+ * Without Link Capabilities 2, i.e., prior to PCIe r3.0, software
+ * should use the Supported Link Speeds field in Link Capabilities,
+ * where only 2.5 GT/s and 5.0 GT/s speeds were defined.
*/
pcie_capability_read_dword(dev, PCI_EXP_LNKCAP2, &lnkcap2);
if (lnkcap2) { /* PCIe r3.0-compliant */
@@ -5575,13 +5579,9 @@ enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev)
pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
if (lnkcap) {
- if (lnkcap & PCI_EXP_LNKCAP_SLS_16_0GB)
- return PCIE_SPEED_16_0GT;
- else if (lnkcap & PCI_EXP_LNKCAP_SLS_8_0GB)
- return PCIE_SPEED_8_0GT;
- else if (lnkcap & PCI_EXP_LNKCAP_SLS_5_0GB)
+ if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_5_0GB)
return PCIE_SPEED_5_0GT;
- else if (lnkcap & PCI_EXP_LNKCAP_SLS_2_5GB)
+ else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_2_5GB)
return PCIE_SPEED_2_5GT;
}
