Am Mon, 8 Mar 2021 14:20:16 +0200 schrieb Andy Shevchenko <[email protected]>:
> From: Jonathan Yong <[email protected]> > > There is already one and at least one more user is coming which > requires an access to Primary to Sideband bridge (P2SB) in order to > get IO or MMIO bar hidden by BIOS. Create a library to access P2SB > for x86 devices. > > Signed-off-by: Jonathan Yong <[email protected]> > Co-developed-by: Andy Shevchenko <[email protected]> > Signed-off-by: Andy Shevchenko <[email protected]> > --- > drivers/pci/Kconfig | 8 ++++ > drivers/pci/Makefile | 1 + > drivers/pci/pci-p2sb.c | 83 > ++++++++++++++++++++++++++++++++++++++++ include/linux/pci-p2sb.h | > 28 ++++++++++++++ 4 files changed, 120 insertions(+) > create mode 100644 drivers/pci/pci-p2sb.c > create mode 100644 include/linux/pci-p2sb.h > > diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig > index 0c473d75e625..740e5b30d6fd 100644 > --- a/drivers/pci/Kconfig > +++ b/drivers/pci/Kconfig > @@ -252,6 +252,14 @@ config PCIE_BUS_PEER2PEER > > endchoice > > +config PCI_P2SB > + bool "Primary to Sideband (P2SB) bridge access support" > + depends on PCI && X86 > + help > + The Primary to Sideband bridge is an interface to some PCI > + devices connected through it. In particular, SPI NOR > + controller in Intel Apollo Lake SoC is one of such devices. > + > source "drivers/pci/hotplug/Kconfig" > source "drivers/pci/controller/Kconfig" > source "drivers/pci/endpoint/Kconfig" > diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile > index d62c4ac4ae1b..eee8d5dda7d9 100644 > --- a/drivers/pci/Makefile > +++ b/drivers/pci/Makefile > @@ -23,6 +23,7 @@ obj-$(CONFIG_PCI_IOV) += iov.o > obj-$(CONFIG_PCI_BRIDGE_EMUL) += pci-bridge-emul.o > obj-$(CONFIG_PCI_LABEL) += pci-label.o > obj-$(CONFIG_X86_INTEL_MID) += pci-mid.o > +obj-$(CONFIG_PCI_P2SB) += pci-p2sb.o > obj-$(CONFIG_PCI_SYSCALL) += syscall.o > obj-$(CONFIG_PCI_STUB) += pci-stub.o > obj-$(CONFIG_PCI_PF_STUB) += pci-pf-stub.o > diff --git a/drivers/pci/pci-p2sb.c b/drivers/pci/pci-p2sb.c > new file mode 100644 > index 000000000000..68d7dad48cdb > --- /dev/null > +++ b/drivers/pci/pci-p2sb.c > @@ -0,0 +1,83 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Primary to Sideband bridge (P2SB) access support > + * > + * Copyright (c) 2017, 2021 Intel Corporation. > + * > + * Authors: Andy Shevchenko <[email protected]> > + * Jonathan Yong <[email protected]> > + */ > + > +#include <linux/bitops.h> > +#include <linux/export.h> > +#include <linux/pci-p2sb.h> > + > +#include <asm/cpu_device_id.h> > +#include <asm/intel-family.h> > + > +#include "pci.h" > + > +#define P2SBC_HIDE_BYTE 0xe1 > +#define P2SBC_HIDE_BIT BIT(0) > + > +static const struct x86_cpu_id p2sb_cpu_ids[] = { > + X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT, > PCI_DEVFN(13, 0)), > + {} > +}; > + > +static int pci_p2sb_devfn(unsigned int *devfn) > +{ > + const struct x86_cpu_id *id; > + > + id = x86_match_cpu(p2sb_cpu_ids); > + if (!id) > + return -ENODEV; > + > + *devfn = (unsigned int)id->driver_data; > + return 0; > +} > + > +/** > + * pci_p2sb_bar - Get Primary to Sideband bridge (P2SB) device BAR > + * @pdev: PCI device to get a PCI bus to communicate with > + * @devfn: PCI slot and function to communicate with > + * @mem: memory resource to be filled in Do we really need that many arguments to it? Before i had, in a platform driver that never had its own pci_dev or bus res->start = simatic_ipc_get_membase0(PCI_DEVFN(13, 0)); if (res-start == 0) return -ENODEV; So helper only asked for the devfn, returned base and no dedicated error code. With this i need struct pci_bus *bus = pci_find_bus(0, 0); struct pci_dev *pci_dev = bus->self; unsigned int magic_i_do_not_want = PCI_DEVFN(13, 0); > + * The BIOS prevents the P2SB device from being enumerated by the PCI > + * subsystem, so we need to unhide and hide it back to lookup the > BAR. > + * > + * Caller must provide a valid pointer to @mem. > + * > + * Locking is handled by pci_rescan_remove_lock mutex. > + * > + * Return: > + * 0 on success or appropriate errno value on error. > + */ > +int pci_p2sb_bar(struct pci_dev *pdev, unsigned int devfn, struct > resource *mem) +{ > + struct pci_bus *bus = pdev->bus; if (!pdev) bus = pci_find_bus(0, 0); Or can we drop the whole arg? > + unsigned int df; > + int ret; > + > + /* Get devfn for P2SB device itself */ > + ret = pci_p2sb_devfn(&df); > + if (ret) > + return ret; if (!devfn) devfn = df; I guess that second devfn is for devices behind that bridge. So unhiding it might reveal several devices? But when caring about that p2sb do i really need to know its devfn. If so i would like to get EXPORT_SYMBOL(pci_p2sb_devfn); regards, Henning > + > + pci_lock_rescan_remove(); > + > + /* Unhide the P2SB device */ > + pci_bus_write_config_byte(bus, df, P2SBC_HIDE_BYTE, 0); > + > + /* Read the first BAR of the device in question */ > + __pci_bus_read_base(bus, devfn, pci_bar_unknown, mem, > PCI_BASE_ADDRESS_0, true); + > + /* Hide the P2SB device */ > + pci_bus_write_config_byte(bus, df, P2SBC_HIDE_BYTE, > P2SBC_HIDE_BIT); + > + pci_unlock_rescan_remove(); > + > + pci_bus_info(bus, devfn, "BAR: %pR\n", mem); > + return 0; > +} > +EXPORT_SYMBOL_GPL(pci_p2sb_bar); > diff --git a/include/linux/pci-p2sb.h b/include/linux/pci-p2sb.h > new file mode 100644 > index 000000000000..15dd42737c84 > --- /dev/null > +++ b/include/linux/pci-p2sb.h > @@ -0,0 +1,28 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * Primary to Sideband bridge (P2SB) access support > + */ > + > +#ifndef _PCI_P2SB_H > +#define _PCI_P2SB_H > + > +#include <linux/errno.h> > + > +struct pci_dev; > +struct resource; > + > +#if IS_BUILTIN(CONFIG_PCI_P2SB) > + > +int pci_p2sb_bar(struct pci_dev *pdev, unsigned int devfn, struct > resource *mem); + > +#else /* CONFIG_PCI_P2SB is not set */ > + > +static inline > +int pci_p2sb_bar(struct pci_dev *pdev, unsigned int devfn, struct > resource *mem) +{ > + return -ENODEV; > +} > + > +#endif /* CONFIG_PCI_P2SB */ > + > +#endif /* _PCI_P2SB_H */
