Reviewed-by: Elad Nachman <enachman@xxxxxxxxxxx> Thanks, Elad. -----Original Message----- From: Pali Rohár <pali@xxxxxxxxxx> Sent: Monday, September 26, 2022 3:35 PM To: Elad Nachman <enachman@xxxxxxxxxxx> Cc: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx>; Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; Krzysztof Wilczyński <kw@xxxxxxxxx>; Rob Herring <robh@xxxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Gregory Clement <gregory.clement@xxxxxxxxxxx>; Marek Behún <kabel@xxxxxxxxxx>; Remi Pommarel <repk@xxxxxxxxxxxx>; Xogium <contact@xxxxxxxxx>; Tomasz Maciej Nowak <tmn505@xxxxxxxxx> Subject: [EXT] Re: [PATCH v2] PCI: aardvark: Implement workaround for PCIe Completion Timeout External Email ---------------------------------------------------------------------- Hello Elad, could you please review this patch? I have implemented it according your instructions, including that full memory barrier as you described. On Tuesday 02 August 2022 14:38:16 Pali Rohár wrote: > Marvell Armada 3700 Functional Errata, Guidelines, and Restrictions > document describes in erratum 3.12 PCIe Completion Timeout (Ref #: > 251), that PCIe IP does not support a strong-ordered model for inbound posted vs. > outbound completion. > > As a workaround for this erratum, DIS_ORD_CHK flag in Debug Mux > Control register must be set. It disables the ordering check in the > core between Completions and Posted requests received from the link. > > Marvell also suggests to do full memory barrier at the beginning of > aardvark summary interrupt handler before calling interrupt handlers > of endpoint drivers in order to minimize the risk for the race > condition documented in the Erratum between the DMA done status > reading and the completion of writing to the host memory. > > More details about this issue and suggested workarounds are in discussion: > https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_l > inux-2Dpci_BN9PR18MB425154FE5019DCAF2028A1D5DB8D9-40BN9PR18MB4251.namp > rd18.prod.outlook.com_t_-23u&d=DwIDaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=eTeNT > LEK5-TxXczjOcKPhANIFtlB9pP4lq9qhdlFrwQ&m=bjgkhgPgOjqCEsbHYHONCZMiFDX72 > MztWaE0AvWBktQVn3zKEDtUdn02Kx_KJ14B&s=SToGsDGEObwbZGilVtVZPyME8jNiRgrq > 4SDYvqqT0TA&e= > > It was reported that enabling this workaround fixes instability issues > and "Unhandled fault" errors when using 60 GHz WiFi 802.11ad card with > Qualcomm > QCA6335 chip under significant load which were caused by interrupt > status stuck in the outbound CMPLT queue traced back to this erratum. > > This workaround fixes also kernel panic triggered after some minutes > of usage 5 GHz WiFi 802.11ax card with Mediatek MT7915 chip: > > Internal error: synchronous external abort: 96000210 [#1] SMP > Kernel panic - not syncing: Fatal exception in interrupt > > Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx> > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx> > Fixes: 8c39d710363c ("PCI: aardvark: Add Aardvark PCI host controller > driver") > Cc: stable@xxxxxxxxxxxxxxx > --- > drivers/pci/controller/pci-aardvark.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/pci/controller/pci-aardvark.c > b/drivers/pci/controller/pci-aardvark.c > index 060936ef01fe..3ae8a85ec72e 100644 > --- a/drivers/pci/controller/pci-aardvark.c > +++ b/drivers/pci/controller/pci-aardvark.c > @@ -210,6 +210,8 @@ enum { > }; > > #define VENDOR_ID_REG (LMI_BASE_ADDR + 0x44) > +#define DEBUG_MUX_CTRL_REG (LMI_BASE_ADDR + 0x208) > +#define DIS_ORD_CHK BIT(30) > > /* PCIe core controller registers */ > #define CTRL_CORE_BASE_ADDR 0x18000 > @@ -558,6 +560,11 @@ static void advk_pcie_setup_hw(struct advk_pcie *pcie) > PCIE_CORE_CTRL2_TD_ENABLE; > advk_writel(pcie, reg, PCIE_CORE_CTRL2_REG); > > + /* Disable ordering checks, workaround for erratum 3.12 "PCIe completion timeout" */ > + reg = advk_readl(pcie, DEBUG_MUX_CTRL_REG); > + reg |= DIS_ORD_CHK; > + advk_writel(pcie, reg, DEBUG_MUX_CTRL_REG); > + > /* Set lane X1 */ > reg = advk_readl(pcie, PCIE_CORE_CTRL0_REG); > reg &= ~LANE_CNT_MSK; > @@ -1581,6 +1588,9 @@ static irqreturn_t advk_pcie_irq_handler(int irq, void *arg) > struct advk_pcie *pcie = arg; > u32 status; > > + /* Full memory barrier (ARM dsb sy), workaround for erratum 3.12 "PCIe completion timeout" */ > + mb(); > + > status = advk_readl(pcie, HOST_CTRL_INT_STATUS_REG); > if (!(status & PCIE_IRQ_CORE_INT)) > return IRQ_NONE; > -- > 2.20.1 >
