Re: [PATCH v2] PCI: Disallow retraining link for Atheros chips on non-Gen1 PCIe bridges

From: Pali Rohár
Date: Fri Apr 30 2021 - 07:41:35 EST

Now I have tested another card ath10k card QCNFA435 (QCA9377 168c:0042)
and after link retraining it cause Synchronous external abort and AER
Uncorrected Non-Fatal error when trying to load ath10k_pci.ko driver.

# insmod /ath10k_pci.ko
[ 45.818017] Internal error: synchronous external abort: 96000210 [#1] SMP
[ 45.825268] Modules linked in: ath10k_pci(+)
[ 45.834695] CPU: 1 PID: 4050 Comm: insmod Not tainted 5.12.0-dirty #934
[ 45.861149] pstate: 60000085 (nZCv daIf -PAN -UAO -TCO BTYPE=--)
[ 45.875585] pc : ath10k_pci_wake_wait+0x48/0xf8 [ath10k_pci]
[ 45.887066] lr : ath10k_pci_wake.part.26+0xe0/0x110 [ath10k_pci]
[ 45.901414] sp : ffffffc014c93820
[ 45.910833] x29: ffffffc014c93820 x28: ffffffc008cc68e0
[ 45.923663] x27: ffffff8000bf20c8 x26: ffffff800e578db8
[ 45.941605] x25: ffffffc008cc62b8 x24: ffffff8000bf2000
[ 45.957488] x23: ffffff800e578db8 x22: 000000000000752f
[ 45.975432] x21: ffffff800e571f20 x20: 0000000000000000
[ 45.995525] x19: 0000000000000005 x18: 0000000000000000
[ 46.011407] x17: 00000000000010f8 x16: 0000000000006400
[ 46.030872] x15: 0000000000000010 x14: 3030373030642065
[ 46.073937] x13: 00000000e8200000 x12: ffffffc010000000
[ 46.079418] x11: ffffffc0117bf000 x10: 00000000e8200000
[ 46.084900] x9 : ffffffc008cc2808 x8 : ffffffc011e00000
[ 46.090380] x7 : ffffff801ffff478 x6 : ffffffc011e00000
[ 46.095861] x5 : ffffffc008cc66a0 x4 : 0000000000200000
[ 46.101342] x3 : 0000000000000000 x2 : 0000000000000001
[ 46.106822] x1 : ffffffc011c80000 x0 : 0000000000080000
[ 46.112304] Call trace:
[ 46.114825] ath10k_pci_wake_wait+0x48/0xf8 [ath10k_pci]
[ 46.120324] ath10k_pci_wake.part.26+0xe0/0x110 [ath10k_pci]
[ 46.126173] ath10k_bus_pci_write32+0x78/0xd0 [ath10k_pci]
[ 46.131841] ath10k_ce_deinit_pipe+0x58/0x218
[ 46.136343] ath10k_pci_probe+0x1fc/0x8a8 [ath10k_pci]
[ 46.141653] pci_device_probe+0xbc/0x170
[ 46.145703] really_probe+0x1bc/0x414
[ 46.149482] driver_probe_device.part.15+0xcc/0x108
[ 46.154513] device_driver_attach+0x80/0x88
[ 46.158831] __driver_attach+0x64/0x120
[ 46.162788] bus_for_each_dev+0x68/0xa0
[ 46.166746] driver_attach+0x28/0x30
[ 46.170433] bus_add_driver+0x188/0x1e8
[ 46.174390] driver_register+0x68/0x118
[ 46.178347] __pci_register_driver+0x48/0x50
[ 46.182751] ath10k_pci_init+0x2c/0x1000 [ath10k_pci]
[ 46.187972] do_one_initcall+0x50/0x218
[ 46.191930] do_init_module+0x5c/0x240
[ 46.195798] load_module+0x1f94/0x24d0
[ 46.199662] __do_sys_init_module+0x120/0x1b8
[ 46.204155] __arm64_sys_init_module+0x20/0x28
[ 46.208738] el0_svc_common.constprop.3+0x90/0x120
[ 46.213682] do_el0_svc+0x74/0x90
[ 46.217101] el0_svc+0x20/0x30
[ 46.220251] el0_sync_handler+0x88/0xb0
[ 46.224209] el0_sync+0x13c/0x140
[ 46.227632] Code: f94216a0 f9400ee1 b9405800 8b000021 (b9400021)
[ 46.233918] ---[ end trace 3619825164cb9b73 ]---
Segmentation fault
[ 46.238818] pcieport 0000:00:00.0: AER: Uncorrected (Non-Fatal) error received: 0000:01:00.0
[ 46.400457] ath10k_pci 0000:01:00.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester ID)
[ 46.412426] ath10k_pci 0000:01:00.0: device [168c:0042] error status/mask=00100000/00400000
[ 46.421248] ath10k_pci 0000:01:00.0: [20] UnsupReq (First)
[ 46.428771] ath10k_pci 0000:01:00.0: AER: TLP Header: 40008001 0000020f e8080004 00000000
[ 46.588115] pcieport 0000:00:00.0: AER: broadcast error_detected message

Adding this card into this quirk list fixes above issues for this card
too. I will send a V3 patch with 168c:0042 in quirk list.

On Tuesday 27 April 2021 12:55:25 Pali Rohár wrote:
> Atheros AR9xxx and QCA98xx chips do not behave not only after a bus reset
> but also after doing retrain link when PCIe bridge is not in GEN1 mode at
> 2.5 GT/s speed.
>
> QCA9880 and QCA9890 chips throw a Link Down event and completely disappear
> from the bus and their config space is not accessible again.
>
> AR9390 chip throws a Link Down event followed by Link Up event, config
> space is accessible again, but contains nonsense values. PCI device ID is
> 0xABCD which indicates HW bug that chip itself was not able to read values
> from internal EEPROM/OTP.
>
> AR9287 chip throws also Link Down and Link Up events, also has accessible
> config space and moreover its config space contains correct values. But
> ath9k driver cannot initialize card from this state as it is unable to
> access HW registers. This also indicates that chip iself was not able to
> read values from internal EEPROM/OTP.
>
> This issue related to PCI device ID 0xABCD and reading internal EEPROM/OTP
> was previously discussed at ath9k-devel mailing list in following thread:
>
> https://www.mail-archive.com/ath9k-devel@xxxxxxxxxxxxxxx/msg07529.html
>
> After experiments we come up with workaround that Retrain link can be
> called only when using GEN1 PCIe bridge or when PCIe bridge has forced link
> speed to 2.5 GT/s via PCI_EXP_LNKCTL2 register.
>
> This issue was reproduced with more cards: Compex WLE900VX (QCA9880 based /
> device ID 0x003c), Compex WLE200NX (AR9287 based / device ID 0x002e),
> "noname" card (QCA9890 based / device ID 0x003c) and Wistron NKR-DNXAH1
> (AR9390 based / device ID 0x0030) on Armada 385 with pci-mvebu.c driver and
> also on Armada 3720 with pci-aardvark.c driver.
>
> To workaround this issue, this change introduces a new PCI quirk called
> PCI_DEV_FLAGS_NO_RETRAIN_LINK_WHEN_NOT_GEN1 which is enabled for all
> Atheros chips with PCI_DEV_FLAGS_NO_BUS_RESET quirk, plus also for Atheros
> chip AR9287.
>
> When this quirk is set then kernel disallows triggering PCI_EXP_LNKCTL_RL
> bit in config space of PCIe Bridge in case PCIe Bridge is capable of higher
> speed than 2.5 GT/s and higher speed is already allowed. When PCIe Bridge
> has accessible LNKCTL2 register then kernel tries to force target link
> speed via PCI_EXP_LNKCTL2_TLS* bits to 2.5 GT/s. After this change it is
> possible to trigger PCI_EXP_LNKCTL_RL bit without causing issues on
> problematic Atheros cards.
>
> Currently only PCIe ASPM kernel code triggers this PCI_EXP_LNKCTL_RL bit,
> so quirk check is added only into pcie/aspm.c file.
>
> Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
> Reported-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> Tested-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> Tested-by: Marek Behún <kabel@xxxxxxxxxx>
> BugLink: https://lore.kernel.org/linux-pci/87h7l8axqp.fsf@xxxxxxx/
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=84821
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=192441
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=209833
> Cc: stable@xxxxxxxxxxxxxxx # c80851f6ce63a ("PCI: Add PCI_EXP_LNKCTL2_TLS* macros")
>
> ---
> Changes since v1:
> * Move whole quirk code into pcie_downgrade_link_to_gen1() function
> * Reformat to 80 chars per line where possible
> * Add quirk also for cards with AR9287 chip (PCI ID 0x002e)
> * Extend commit message description and add information about 0xABCD
> ---
> drivers/pci/pcie/aspm.c | 44 +++++++++++++++++++++++++++++++++++++++++
> drivers/pci/quirks.c | 37 ++++++++++++++++++++++++++--------
> include/linux/pci.h | 2 ++
> 3 files changed, 75 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index ac0557a305af..729b0389562b 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -192,12 +192,56 @@ static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
> link->clkpm_disable = blacklist ? 1 : 0;
> }
>
> +static int pcie_downgrade_link_to_gen1(struct pci_dev *parent)
> +{
> + u16 reg16;
> + u32 reg32;
> + int ret;
> +
> + /* Check if link is capable of higher speed than 2.5 GT/s */
> + pcie_capability_read_dword(parent, PCI_EXP_LNKCAP, &reg32);
> + if ((reg32 & PCI_EXP_LNKCAP_SLS) <= PCI_EXP_LNKCAP_SLS_2_5GB)
> + return 0;
> +
> + /* Check if link speed can be downgraded to 2.5 GT/s */
> + pcie_capability_read_dword(parent, PCI_EXP_LNKCAP2, &reg32);
> + if (!(reg32 & PCI_EXP_LNKCAP2_SLS_2_5GB)) {
> + pci_err(parent, "ASPM: Bridge does not support changing Link Speed to 2.5 GT/s\n");
> + return -EOPNOTSUPP;
> + }
> +
> + /* Force link speed to 2.5 GT/s */
> + ret = pcie_capability_clear_and_set_word(parent, PCI_EXP_LNKCTL2,
> + PCI_EXP_LNKCTL2_TLS,
> + PCI_EXP_LNKCTL2_TLS_2_5GT);
> + if (!ret) {
> + /* Verify that new value was really set */
> + pcie_capability_read_word(parent, PCI_EXP_LNKCTL2, &reg16);
> + if ((reg16 & PCI_EXP_LNKCTL2_TLS) != PCI_EXP_LNKCTL2_TLS_2_5GT)
> + ret = -EINVAL;
> + }
> +
> + if (ret) {
> + pci_err(parent, "ASPM: Changing Target Link Speed to 2.5 GT/s failed: %d\n", ret);
> + return ret;
> + }
> +
> + pci_info(parent, "ASPM: Target Link Speed changed to 2.5 GT/s due to quirk\n");
> + return 0;
> +}
> +
> static bool pcie_retrain_link(struct pcie_link_state *link)
> {
> struct pci_dev *parent = link->pdev;
> unsigned long end_jiffies;
> u16 reg16;
>
> + if ((link->downstream->dev_flags & PCI_DEV_FLAGS_NO_RETRAIN_LINK_WHEN_NOT_GEN1) &&
> + pcie_downgrade_link_to_gen1(parent)) {
> + pci_err(parent, "ASPM: Retrain Link at higher speed is disallowed by quirk\n");
> + return false;
> + }
> +
> pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
> reg16 |= PCI_EXP_LNKCTL_RL;
> pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 653660e3ba9e..68c5e8f4ff8c 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3553,23 +3553,44 @@ static void mellanox_check_broken_intx_masking(struct pci_dev *pdev)
> DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_MELLANOX, PCI_ANY_ID,
> mellanox_check_broken_intx_masking);
>
> -static void quirk_no_bus_reset(struct pci_dev *dev)
> +static void quirk_no_bus_reset_and_no_retrain_link(struct pci_dev *dev)
> {
> - dev->dev_flags |= PCI_DEV_FLAGS_NO_BUS_RESET;
> + dev->dev_flags |= PCI_DEV_FLAGS_NO_BUS_RESET |
> + PCI_DEV_FLAGS_NO_RETRAIN_LINK_WHEN_NOT_GEN1;
> }
>
> /*
> - * Some Atheros AR9xxx and QCA988x chips do not behave after a bus reset.
> + * Atheros AR9xxx and QCA98xx chips do not behave after a bus reset and also
> + * after retrain link when PCIe bridge is not in GEN1 mode at 2.5 GT/s speed.
> * The device will throw a Link Down error on AER-capable systems and
> * regardless of AER, config space of the device is never accessible again
> * and typically causes the system to hang or reset when access is attempted.
> + * Or if config space is accessible again then it contains only dummy values
> + * like fixed PCI device ID 0xABCD or values not initialized at all.
> + * Retrain link can be called only when using GEN1 PCIe bridge or when
> + * PCIe bridge has forced link speed to 2.5 GT/s via PCI_EXP_LNKCTL2 register.
> + * To reset these cards it is required to do PCIe Warm Reset via PERST# pin.
> * https://lore.kernel.org/r/20140923210318.498dacbd@xxxxxxxxxxxxxx/
> + * https://lore.kernel.org/r/87h7l8axqp.fsf@xxxxxxx/
> + * https://www.mail-archive.com/ath9k-devel@xxxxxxxxxxxxxxx/msg07529.html
> */
> -DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0030, quirk_no_bus_reset);
> -DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0032, quirk_no_bus_reset);
> -DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x003c, quirk_no_bus_reset);
> -DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0033, quirk_no_bus_reset);
> -DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0034, quirk_no_bus_reset);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x002e,
> + quirk_no_bus_reset_and_no_retrain_link);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0030,
> + quirk_no_bus_reset_and_no_retrain_link);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0032,
> + quirk_no_bus_reset_and_no_retrain_link);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0033,
> + quirk_no_bus_reset_and_no_retrain_link);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0034,
> + quirk_no_bus_reset_and_no_retrain_link);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x003c,
> + quirk_no_bus_reset_and_no_retrain_link);
> +
> +static void quirk_no_bus_reset(struct pci_dev *dev)
> +{
> + dev->dev_flags |= PCI_DEV_FLAGS_NO_BUS_RESET;
> +}
>
> /*
> * Root port on some Cavium CN8xxx chips do not successfully complete a bus
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 86c799c97b77..fdbf7254e4ab 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -227,6 +227,8 @@ enum pci_dev_flags {
> PCI_DEV_FLAGS_NO_FLR_RESET = (__force pci_dev_flags_t) (1 << 10),
> /* Don't use Relaxed Ordering for TLPs directed at this device */
> PCI_DEV_FLAGS_NO_RELAXED_ORDERING = (__force pci_dev_flags_t) (1 << 11),
> + /* Don't Retrain Link for device when bridge is not in GEN1 mode */
> + PCI_DEV_FLAGS_NO_RETRAIN_LINK_WHEN_NOT_GEN1 = (__force pci_dev_flags_t) (1 << 12),
> };
>
> enum pci_irq_reroute_variant {
> --
> 2.20.1
>