Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756867AbbFRUCX (ORCPT ); Thu, 18 Jun 2015 16:02:23 -0400 Received: from mail-ie0-f182.google.com ([209.85.223.182]:36129 "EHLO mail-ie0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754641AbbFRUCO (ORCPT ); Thu, 18 Jun 2015 16:02:14 -0400 Date: Thu, 18 Jun 2015 15:02:10 -0500 From: Bjorn Helgaas To: Duc Dang Cc: linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Ian Campbell , Marcin Juszkiewicz , Tanmay Inamdar , patches@apm.com Subject: Re: [PATCH v2 1/1] PCI: X-Gene: Disable Configuration Request Retry Status for X-Gene v1 PCIe Message-ID: <20150618200210.GH7710@google.com> References: <017c1ec8e3f43f86a947eaddb30c9389e0b1053b.1434154377.git.dhdang@apm.com> <20150618175553.GF7710@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150618175553.GF7710@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5401 Lines: 137 On Thu, Jun 18, 2015 at 12:55:53PM -0500, Bjorn Helgaas wrote: > On Fri, Jun 12, 2015 at 05:35:57PM -0700, Duc Dang wrote: > > X-Gene v1 PCIe controller has a bug in Configuration Request Retry > > Status (CRS) logic: > > When CPU tries to read Vendor ID and Device ID of not-existed > > remote device, the controller returns 0xFFFF0001 instead of > > 0xFFFFFFFF; this will add significant delay in boot time as > > pci_bus_read_dev_vendor_id will wait for 60 seconds before > > giving up. > > > > So for X-Gene v1 PCIe controllers, disable CRS capability > > advertisement by clearing CRS Software Visibility bit before > > returning the Root Capability value to the callers. This is done > > by implementing X-Gene PCIe specific xgene_pcie_config_read32 for > > CFG read accesses to replace the generic default pci_generic_config_read32 > > function. > > > > v2 changes: > > Use pci_generic_config_read32 to implement xgene_pcie_config_read32 > > > > Signed-off-by: Duc Dang > > Tested-by: Ian Campbell > > Tested-by: Marcin Juszkiewicz > > I'd like to merge this (as amended below) for v4.2. But I'm looking for an > ack from Tanmay, and I'm still waiting for the second patch to remove the > link_up test. > > Bjorn Applied to pci/host-xgene for v4.2, thanks very much! > commit 49ac8c566d7a37f9f295e1fd4fbdd96517f22d55 > Author: Duc Dang > Date: Fri Jun 12 17:35:57 2015 -0700 > > PCI: xgene: Disable Configuration Request Retry Status for v1 silicon > > When a CPU reads the Vendor and Device ID of a non-existent device, the > controller should fabricate return data of 0xFFFFFFFF. Configuration > Request Retry Status (CRS) is not applicable in this case because the > device doesn't exist at all. > > The X-Gene v1 PCIe controller has a bug in the CRS logic such that when CRS > is enabled, it fabricates return data of 0xFFFF0001 for this case, which > means "the device exists but is not ready." That causes the PCI core to > retry the read until it times out after 60 seconds. > > Disable CRS capability advertisement by clearing the CRS Software > Visibility bit in the Root Capabilities Register. > > [bhelgaas: changelog and comment] > Tested-by: Ian Campbell > Tested-by: Marcin Juszkiewicz > Signed-off-by: Duc Dang > Signed-off-by: Bjorn Helgaas > > diff --git a/drivers/pci/host/pci-xgene.c b/drivers/pci/host/pci-xgene.c > index 3e5a636..70af714 100644 > --- a/drivers/pci/host/pci-xgene.c > +++ b/drivers/pci/host/pci-xgene.c > @@ -59,6 +59,12 @@ > #define SZ_1T (SZ_1G*1024ULL) > #define PIPE_PHY_RATE_RD(src) ((0xc000 & (u32)(src)) >> 0xe) > > +#define ROOT_CAP_AND_CTRL 0x5C > + > +/* PCIe IP version */ > +#define XGENE_PCIE_IP_VER_UNKN 0 > +#define XGENE_PCIE_IP_VER_1 1 > + > struct xgene_pcie_port { > struct device_node *node; > struct device *dev; > @@ -67,6 +73,7 @@ struct xgene_pcie_port { > void __iomem *cfg_base; > unsigned long cfg_addr; > bool link_up; > + u32 version; > }; > > static inline u32 pcie_bar_low_val(u32 addr, u32 flags) > @@ -140,9 +147,37 @@ static void __iomem *xgene_pcie_map_bus(struct pci_bus *bus, unsigned int devfn, > return xgene_pcie_get_cfg_base(bus) + offset; > } > > +static int xgene_pcie_config_read32(struct pci_bus *bus, unsigned int devfn, > + int where, int size, u32 *val) > +{ > + struct xgene_pcie_port *port = bus->sysdata; > + > + if (pci_generic_config_read32(bus, devfn, where & ~0x3, 4, val) != > + PCIBIOS_SUCCESSFUL) > + return PCIBIOS_DEVICE_NOT_FOUND; > + > + /* > + * The v1 controller has a bug in its Configuration Request > + * Retry Status (CRS) logic: when CRS is enabled and we read the > + * Vendor and Device ID of a non-existent device, the controller > + * fabricates return data of 0xFFFF0001 ("device exists but is not > + * ready") instead of 0xFFFFFFFF ("device does not exist"). This > + * causes the PCI core to retry the read until it times out. > + * Avoid this by not claiming to support CRS. > + */ > + if (pci_is_root_bus(bus) && (port->version == XGENE_PCIE_IP_VER_1) && > + ((where & ~0x3) == ROOT_CAP_AND_CTRL)) > + *val &= ~(PCI_EXP_RTCAP_CRSVIS << 16); > + > + if (size <= 2) > + *val = (*val >> (8 * (where & 3))) & ((1 << (size * 8)) - 1); > + > + return PCIBIOS_SUCCESSFUL; > +} > + > static struct pci_ops xgene_pcie_ops = { > .map_bus = xgene_pcie_map_bus, > - .read = pci_generic_config_read32, > + .read = xgene_pcie_config_read32, > .write = pci_generic_config_write32, > }; > > @@ -500,6 +535,10 @@ static int xgene_pcie_probe_bridge(struct platform_device *pdev) > port->node = of_node_get(pdev->dev.of_node); > port->dev = &pdev->dev; > > + port->version = XGENE_PCIE_IP_VER_UNKN; > + if (of_device_is_compatible(port->node, "apm,xgene-pcie")) > + port->version = XGENE_PCIE_IP_VER_1; > + > ret = xgene_pcie_map_reg(port, pdev); > if (ret) > return ret; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/