On Sun, Aug 6, 2023 at 11:16 AM Florian Fainelli <florian.fainelli@xxxxxxxxxxxx> wrote: > > > > On 8/5/2023 9:44 PM, Lukas Wunner wrote: > > The Broadcom Set Top Box PCIe controller signals an Asynchronous SError > > Interrupt and thus causes a kernel panic when non-posted transactions > > time out. This differs from most other PCIe controllers which return a > > fabricated "all ones" response instead. > > > > To avoid gratuitous kernel panics, the driver reads the link status from > > a proprietary PCIE_MISC_PCIE_STATUS register and skips downstream > > accesses if the link is down. > > > > However the bits in the proprietary register may purport that the link > > is up even though link training is still in progress (as indicated by > > the Link Training bit in the Link Status register). > > > > This has been observed with various PCIe switches attached to a BCM2711 > > (Raspberry Pi CM4): The issue is most pronounced with the Pericom > > PI7C9X2G404SV, but has also occasionally been witnessed with the Pericom > > PI7C9X2G404SL and ASMedia ASM1184e. > > > > Check the Link Training bit in addition to the PCIE_MISC_PCIE_STATUS > > register before performing downstream accesses. > > > > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> > > Cc: <stable@xxxxxxxxxxxxxxx> > > Since you CC stable, it would be neat to provide a Fixes: tag here, most > likely this dates back from the original commit adding support for this > driver. > > > --- > > drivers/pci/controller/pcie-brcmstb.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c > > index f593a422bd63..b4abfced8e9b 100644 > > --- a/drivers/pci/controller/pcie-brcmstb.c > > +++ b/drivers/pci/controller/pcie-brcmstb.c > > @@ -679,8 +679,10 @@ static bool brcm_pcie_link_up(struct brcm_pcie *pcie) > > u32 val = readl(pcie->base + PCIE_MISC_PCIE_STATUS); > > u32 dla = FIELD_GET(PCIE_MISC_PCIE_STATUS_PCIE_DL_ACTIVE_MASK, val); > > u32 plu = FIELD_GET(PCIE_MISC_PCIE_STATUS_PCIE_PHYLINKUP_MASK, val); > > + u16 lnksta = readw(pcie->base + BRCM_PCIE_CAP_REGS + PCI_EXP_LNKSTA); > > + u16 lt = FIELD_GET(PCI_EXP_LNKSTA_LT, lnksta); > > > > - return dla && plu; > > + return dla && plu && !lt; > > The patch looks good to me in spirit though I want Jim to review and This looks good to me but please allow me a few days to do some testing -- I'm currently in Covid prison. Regards, Jim Quinlan Broadcom STB > provide feedback here since he was looking at this sort of issues not so > long ago. > > Thanks for tracking this down! > -- > Florian
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