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Date: Mon, 14 Nov 2016 15:52:08 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Ray Jui <ray.jui@...adcom.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org,
bcm-kernel-feedback-list@...adcom.com, linux-pci@...r.kernel.org,
Alex Barba <alex.barba@...adcom.com>,
Oza Oza <oza.oza@...adcom.com>
Subject: Re: [PATCH v2 04/12] PCI: iproc: Fix exception with multi-function
devices
On Mon, Oct 31, 2016 at 05:38:33PM -0700, Ray Jui wrote:
> During enumeration with multi-function EP devices, access to the
> configuration space of a non-exist function results in an unsupported
> request being returned as expected. By default the PAXB based iProc
> PCIe controller forwards this as an APB error to the host system and
> that causes an exception, which is undesired
>
> This patch disables this undesired behaviour and lets the kernel PCI
> stack deals with an access to the non-exist function, in which case
> a vendor ID of 0xffff is returned and handled gracefully
>
> Reported-by: JD Zheng <jiandong.zheng@...adcom.com>
> Signed-off-by: Ray Jui <ray.jui@...adcom.com>
> Reviewed-by: JD Zheng <jiandong.zheng@...adcom.com>
> Reviewed-by: Oza Oza <oza.oza@...adcom.com>
> Reviewed-by: Scott Branden <scott.branden@...adcom.com>
> ---
> drivers/pci/host/pcie-iproc.c | 58 +++++++++++++++++++++++++++++++++++++++++--
> drivers/pci/host/pcie-iproc.h | 3 +++
> 2 files changed, 59 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/host/pcie-iproc.c b/drivers/pci/host/pcie-iproc.c
> index f3b3340..07ec478 100644
> --- a/drivers/pci/host/pcie-iproc.c
> +++ b/drivers/pci/host/pcie-iproc.c
> @@ -58,6 +58,9 @@
> #define PCIE_DL_ACTIVE_SHIFT 2
> #define PCIE_DL_ACTIVE BIT(PCIE_DL_ACTIVE_SHIFT)
>
> +#define APB_ERR_EN_SHIFT 0
> +#define APB_ERR_EN BIT(APB_ERR_EN_SHIFT)
> +
> #define OARR_VALID_SHIFT 0
> #define OARR_VALID BIT(OARR_VALID_SHIFT)
> #define OARR_SIZE_CFG_SHIFT 1
> @@ -96,6 +99,9 @@ enum iproc_pcie_reg {
> /* link status */
> IPROC_PCIE_LINK_STATUS,
>
> + /* enable APB error for unsupported requests */
> + IPROC_PCIE_APB_ERR_EN,
> +
> /* total number of core registers */
> IPROC_PCIE_MAX_NUM_REG,
> };
> @@ -124,6 +130,7 @@ static const u16 iproc_pcie_reg_paxb[] = {
> [IPROC_PCIE_OMAP_LO] = 0xd40,
> [IPROC_PCIE_OMAP_HI] = 0xd44,
> [IPROC_PCIE_LINK_STATUS] = 0xf0c,
> + [IPROC_PCIE_APB_ERR_EN] = 0xf40,
> };
>
> /* iProc PCIe PAXC v1 registers */
> @@ -181,6 +188,28 @@ static inline void iproc_pcie_write_reg(struct iproc_pcie *pcie,
> writel(val, pcie->base + offset);
> }
>
> +/**
> + * APB error forwarding can be disabled during access of configuration
> + * registers of the endpoint device, to prevent unsupported requests
> + * (typically seen during enumeration with multi-function devices) from
> + * triggering a system exception
> + */
> +static inline void iproc_pcie_apb_err_disable(struct pci_bus *bus,
> + bool disable)
> +{
> + struct iproc_pcie *pcie = iproc_data(bus);
> + u32 val;
> +
> + if (bus->number && pcie->has_apb_err_disable) {
> + val = iproc_pcie_read_reg(pcie, IPROC_PCIE_APB_ERR_EN);
> + if (disable)
> + val &= ~APB_ERR_EN;
> + else
> + val |= APB_ERR_EN;
> + iproc_pcie_write_reg(pcie, IPROC_PCIE_APB_ERR_EN, val);
> + }
> +}
> +
> static inline void iproc_pcie_ob_write(struct iproc_pcie *pcie,
> enum iproc_pcie_reg reg,
> unsigned window, u32 val)
> @@ -244,10 +273,34 @@ static void __iomem *iproc_pcie_map_cfg_bus(struct pci_bus *bus,
> return (pcie->base + offset);
> }
>
> +static int iproc_pcie_config_read32(struct pci_bus *bus, unsigned int devfn,
> + int where, int size, u32 *val)
> +{
> + int ret;
> +
> + iproc_pcie_apb_err_disable(bus, true);
> + ret = pci_generic_config_read32(bus, devfn, where, size, val);
> + iproc_pcie_apb_err_disable(bus, false);
I guess this means that any other APB errors (unrelated to this config
access, e.g., a driver doing MMIo to a device at the same time the user is
doing "lspci") that happen to occur during this window will also be
ignored.
> +
> + return ret;
> +}
> +
> +static int iproc_pcie_config_write32(struct pci_bus *bus, unsigned int devfn,
> + int where, int size, u32 val)
> +{
> + int ret;
> +
> + iproc_pcie_apb_err_disable(bus, true);
> + ret = pci_generic_config_write32(bus, devfn, where, size, val);
> + iproc_pcie_apb_err_disable(bus, false);
> +
> + return ret;
> +}
> +
> static struct pci_ops iproc_pcie_ops = {
> .map_bus = iproc_pcie_map_cfg_bus,
> - .read = pci_generic_config_read32,
> - .write = pci_generic_config_write32,
> + .read = iproc_pcie_config_read32,
> + .write = iproc_pcie_config_write32,
> };
>
> static void iproc_pcie_reset(struct iproc_pcie *pcie)
> @@ -485,6 +538,7 @@ static int iproc_pcie_rev_init(struct iproc_pcie *pcie)
> break;
> case IPROC_PCIE_PAXB:
> regs = iproc_pcie_reg_paxb;
> + pcie->has_apb_err_disable = true;
> break;
> case IPROC_PCIE_PAXC:
> regs = iproc_pcie_reg_paxc;
> diff --git a/drivers/pci/host/pcie-iproc.h b/drivers/pci/host/pcie-iproc.h
> index 768be05..711dd3a 100644
> --- a/drivers/pci/host/pcie-iproc.h
> +++ b/drivers/pci/host/pcie-iproc.h
> @@ -57,6 +57,8 @@ struct iproc_msi;
> * @phy: optional PHY device that controls the Serdes
> * @map_irq: function callback to map interrupts
> * @ep_is_internal: indicates an internal emulated endpoint device is connected
> + * @has_apb_err_disable: indicates the controller can be configured to prevent
> + * unsupported request from being forwarded as an APB bus error
> * @need_ob_cfg: indicates SW needs to configure the outbound mapping window
> * @ob: outbound mapping parameters
> * @msi: MSI data
> @@ -74,6 +76,7 @@ struct iproc_pcie {
> struct phy *phy;
> int (*map_irq)(const struct pci_dev *, u8, u8);
> bool ep_is_internal;
> + bool has_apb_err_disable;
> bool need_ob_cfg;
> struct iproc_pcie_ob ob;
> struct iproc_msi *msi;
> --
> 2.1.4
>
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