Subject: [PATCH v2] PCI: aardvark: Implement workaround for PCIe Completion Timeout Date: Tue, 2 Aug 2022 14:38:16 +0200 Message-Id: <20220802123816.21817-1-pali@kernel.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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://lore.kernel.org/linux-pci/BN9PR18MB425154FE5019DCAF2028A1D5DB8D9@BN9PR18MB4251.namprd18.prod.outlook.com/t/#u 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 Signed-off-by: Pali Rohár Fixes: 8c39d710363c ("PCI: aardvark: Add Aardvark PCI host controller driver") Cc: stable@vger.kernel.org --- drivers/pci/controller/pci-aardvark.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- 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 ad 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; @@ -1580,6 +1587,9 @@ static irqreturn_t advk_pcie_irq_handler 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;