[RFC PATCH 00/20] Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb())

[Will Deacon <will.deacon@arm.com>]

Hi all,

This series attempts to remove explicit mmiowb() calls from driver code,
instead adding it to spin_unlock() for architectures that require it.

The infamous "PowerPC trick" was found to be flawed, so a correct but probably
slower version is made generic for architectures wishing to use it. I've ported
RISC-V over to this interface, and hooked up PowerPC to the generic
infrastructure but with their existing implementation. Other architectures that
require a definition for mmiowb() now have it unconditionally called from their
spin_unlock() code. If this is deemed to be expensive, they should be able to
do something similar to RISC-V.

I used coccinelle to remove the vast majority of the users, and the trivial
spatch invocation is included in the commit message of that patch. I've also
*build-tested* this for RISC-V, ia64, mips64, sh, powerpc64 and arm64.

This is based on a couple of other I/O-related series that I have pending:

  https://lkml.org/lkml/2019/2/22/484
  https://lkml.org/lkml/2019/2/22/500

so I've pushed the whole lot out on a branch for your comfort and convenience:

  git://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git io

Feedback welcome,

Will

Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Daniel Lustig <dlustig@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Tony Luck <tony.luck@intel.com>

--->8

Will Deacon (20):
  asm-generic/mmiowb: Add generic implementation of mmiowb() tracking
  arch: Use asm-generic header for asm/mmiowb.h
  mmiowb: Hook up mmiowb helpers to spinlocks and generic I/O accessors
  ARM: io: Remove useless definition of mmiowb()
  arm64: io: Remove useless definition of mmiowb()
  x86: io: Remove useless definition of mmiowb()
  nds32: io: Remove useless definition of mmiowb()
  m68k: io: Remove useless definition of mmiowb()
  sh: Add unconditional mmiowb() to arch_spin_unlock()
  mips: Add unconditional mmiowb() to arch_spin_unlock()
  ia64: Add unconditional mmiowb() to arch_spin_unlock()
  powerpc: mmiowb: Hook up mmwiob() implementation to asm-generic code
  riscv: mmiowb: Hook up mmwiob() implementation to asm-generic code
  Documentation: Kill all references to mmiowb()
  drivers: Remove useless trailing comments from mmiowb() invocations
  drivers: Remove explicit invocations of mmiowb()
  scsi: qla1280: Remove stale comment about mmiowb()
  i40iw: Redefine i40iw_mmiowb() to do nothing
  net: silan: sc92031: Remove stale comment about mmiowb()
  arch: Remove dummy mmiowb() definitions from arch code

 Documentation/driver-api/device-io.rst             |  45 ---------
 Documentation/driver-api/pci/p2pdma.rst            |   4 -
 Documentation/memory-barriers.txt                  | 103 +--------------------
 arch/alpha/include/asm/Kbuild                      |   1 +
 arch/alpha/include/asm/io.h                        |   2 -
 arch/arc/include/asm/Kbuild                        |   1 +
 arch/arm/include/asm/Kbuild                        |   1 +
 arch/arm/include/asm/io.h                          |   2 -
 arch/arm64/include/asm/Kbuild                      |   1 +
 arch/arm64/include/asm/io.h                        |   2 -
 arch/c6x/include/asm/Kbuild                        |   1 +
 arch/csky/include/asm/Kbuild                       |   1 +
 arch/h8300/include/asm/Kbuild                      |   1 +
 arch/hexagon/include/asm/Kbuild                    |   1 +
 arch/hexagon/include/asm/io.h                      |   2 -
 arch/ia64/include/asm/io.h                         |   4 -
 arch/ia64/include/asm/mmiowb.h                     |  12 +++
 arch/ia64/include/asm/spinlock.h                   |   2 +
 arch/m68k/include/asm/Kbuild                       |   1 +
 arch/m68k/include/asm/io_mm.h                      |   2 -
 arch/microblaze/include/asm/Kbuild                 |   1 +
 arch/mips/include/asm/io.h                         |   3 -
 arch/mips/include/asm/mmiowb.h                     |  11 +++
 arch/mips/include/asm/spinlock.h                   |  15 +++
 arch/nds32/include/asm/Kbuild                      |   1 +
 arch/nds32/include/asm/io.h                        |   2 -
 arch/nios2/include/asm/Kbuild                      |   1 +
 arch/openrisc/include/asm/Kbuild                   |   1 +
 arch/parisc/include/asm/Kbuild                     |   1 +
 arch/parisc/include/asm/io.h                       |   2 -
 arch/powerpc/Kconfig                               |   1 +
 arch/powerpc/include/asm/io.h                      |  33 +------
 arch/powerpc/include/asm/mmiowb.h                  |  41 ++++++++
 arch/powerpc/include/asm/spinlock.h                |  17 ----
 arch/riscv/Kconfig                                 |   1 +
 arch/riscv/include/asm/io.h                        |  15 +--
 arch/riscv/include/asm/mmiowb.h                    |  14 +++
 arch/s390/include/asm/Kbuild                       |   1 +
 arch/sh/include/asm/io.h                           |   3 -
 arch/sh/include/asm/mmiowb.h                       |  12 +++
 arch/sh/include/asm/spinlock-llsc.h                |   2 +
 arch/sparc/include/asm/Kbuild                      |   1 +
 arch/sparc/include/asm/io_64.h                     |   2 -
 arch/um/include/asm/Kbuild                         |   1 +
 arch/unicore32/include/asm/Kbuild                  |   1 +
 arch/x86/include/asm/io.h                          |   2 -
 arch/xtensa/include/asm/Kbuild                     |   1 +
 drivers/crypto/cavium/nitrox/nitrox_reqmgr.c       |   4 -
 drivers/dma/txx9dmac.c                             |   3 -
 drivers/firewire/ohci.c                            |   1 -
 drivers/gpu/drm/i915/intel_hdmi.c                  |  10 --
 drivers/ide/tx4939ide.c                            |   2 -
 drivers/infiniband/hw/hfi1/chip.c                  |   3 -
 drivers/infiniband/hw/hfi1/pio.c                   |   1 -
 drivers/infiniband/hw/hns/hns_roce_hw_v1.c         |   2 -
 drivers/infiniband/hw/i40iw/i40iw_osdep.h          |   2 +-
 drivers/infiniband/hw/mlx4/qp.c                    |   6 --
 drivers/infiniband/hw/mlx5/qp.c                    |   1 -
 drivers/infiniband/hw/mthca/mthca_cmd.c            |   6 --
 drivers/infiniband/hw/mthca/mthca_cq.c             |   5 -
 drivers/infiniband/hw/mthca/mthca_qp.c             |  17 ----
 drivers/infiniband/hw/mthca/mthca_srq.c            |   6 --
 drivers/infiniband/hw/qedr/verbs.c                 |  12 ---
 drivers/infiniband/hw/qib/qib_iba6120.c            |   4 -
 drivers/infiniband/hw/qib/qib_iba7220.c            |   3 -
 drivers/infiniband/hw/qib/qib_iba7322.c            |   3 -
 drivers/infiniband/hw/qib/qib_sd7220.c             |   4 -
 drivers/media/pci/dt3155/dt3155.c                  |   8 --
 drivers/memstick/host/jmb38x_ms.c                  |   4 -
 drivers/misc/ioc4.c                                |   2 -
 drivers/misc/mei/hw-me.c                           |   3 -
 drivers/misc/tifm_7xx1.c                           |   1 -
 drivers/mmc/host/alcor.c                           |   1 -
 drivers/mmc/host/sdhci.c                           |  13 ---
 drivers/mmc/host/tifm_sd.c                         |   3 -
 drivers/mmc/host/via-sdmmc.c                       |  10 --
 drivers/mtd/nand/raw/r852.c                        |   2 -
 drivers/mtd/nand/raw/txx9ndfmc.c                   |   1 -
 drivers/net/ethernet/aeroflex/greth.c              |   1 -
 drivers/net/ethernet/alacritech/slicoss.c          |   4 -
 drivers/net/ethernet/amazon/ena/ena_com.c          |   1 -
 drivers/net/ethernet/atheros/atlx/atl1.c           |   1 -
 drivers/net/ethernet/atheros/atlx/atl2.c           |   1 -
 drivers/net/ethernet/broadcom/bnx2.c               |   4 -
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c    |   2 -
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.h    |   4 -
 .../net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c    |   1 -
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c   |  29 ------
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c     |   1 -
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c  |   2 -
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_vfpf.c   |   4 -
 drivers/net/ethernet/broadcom/bnxt/bnxt.c          |   3 -
 drivers/net/ethernet/broadcom/tg3.c                |   6 --
 .../net/ethernet/cavium/liquidio/cn66xx_device.c   |  10 --
 .../net/ethernet/cavium/liquidio/octeon_device.c   |   1 -
 drivers/net/ethernet/cavium/liquidio/octeon_droq.c |   4 -
 .../net/ethernet/cavium/liquidio/request_manager.c |   1 -
 drivers/net/ethernet/intel/e1000/e1000_main.c      |   5 -
 drivers/net/ethernet/intel/e1000e/netdev.c         |   7 --
 drivers/net/ethernet/intel/fm10k/fm10k_iov.c       |   2 -
 drivers/net/ethernet/intel/fm10k/fm10k_main.c      |   5 -
 drivers/net/ethernet/intel/i40e/i40e_txrx.c        |   5 -
 drivers/net/ethernet/intel/iavf/iavf_txrx.c        |   5 -
 drivers/net/ethernet/intel/ice/ice_txrx.c          |   5 -
 drivers/net/ethernet/intel/igb/igb_main.c          |   5 -
 drivers/net/ethernet/intel/igbvf/netdev.c          |   4 -
 drivers/net/ethernet/intel/igc/igc_main.c          |   5 -
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c      |   5 -
 drivers/net/ethernet/marvell/sky2.c                |   4 -
 drivers/net/ethernet/mellanox/mlx4/catas.c         |   4 -
 drivers/net/ethernet/mellanox/mlx4/cmd.c           |  13 ---
 drivers/net/ethernet/mellanox/mlx5/core/cmd.c      |   1 -
 drivers/net/ethernet/myricom/myri10ge/myri10ge.c   |   2 -
 drivers/net/ethernet/neterion/s2io.c               |   2 -
 drivers/net/ethernet/neterion/vxge/vxge-main.c     |   5 -
 drivers/net/ethernet/neterion/vxge/vxge-traffic.c  |   4 -
 drivers/net/ethernet/qlogic/qed/qed_int.c          |  13 ---
 drivers/net/ethernet/qlogic/qed/qed_spq.c          |   3 -
 drivers/net/ethernet/qlogic/qede/qede_ethtool.c    |   8 --
 drivers/net/ethernet/qlogic/qede/qede_fp.c         |   8 --
 drivers/net/ethernet/qlogic/qla3xxx.c              |   1 -
 drivers/net/ethernet/qlogic/qlge/qlge.h            |   1 -
 drivers/net/ethernet/qlogic/qlge/qlge_main.c       |   1 -
 drivers/net/ethernet/realtek/r8169.c               |   5 -
 drivers/net/ethernet/renesas/ravb_main.c           |   9 --
 drivers/net/ethernet/renesas/ravb_ptp.c            |   3 -
 drivers/net/ethernet/renesas/sh_eth.c              |   1 -
 drivers/net/ethernet/sfc/falcon/io.h               |   2 -
 drivers/net/ethernet/sfc/io.h                      |   2 -
 drivers/net/ethernet/silan/sc92031.c               |  15 ---
 drivers/net/ethernet/via/via-rhine.c               |   3 -
 drivers/net/ethernet/wiznet/w5100.c                |   6 --
 drivers/net/ethernet/wiznet/w5300.c                |  15 ---
 drivers/net/wireless/ath/ath5k/base.c              |   4 -
 drivers/net/wireless/ath/ath5k/mac80211-ops.c      |   2 -
 drivers/net/wireless/broadcom/b43/main.c           |   7 --
 drivers/net/wireless/broadcom/b43/sysfs.c          |   1 -
 drivers/net/wireless/broadcom/b43legacy/ilt.c      |   2 -
 drivers/net/wireless/broadcom/b43legacy/main.c     |  20 ----
 drivers/net/wireless/broadcom/b43legacy/phy.c      |   1 -
 drivers/net/wireless/broadcom/b43legacy/pio.h      |   1 -
 drivers/net/wireless/broadcom/b43legacy/radio.c    |   4 -
 drivers/net/wireless/broadcom/b43legacy/sysfs.c    |   1 -
 drivers/net/wireless/intel/iwlegacy/common.h       |   7 --
 drivers/net/wireless/intel/iwlwifi/pcie/trans.c    |   1 -
 drivers/ntb/hw/idt/ntb_hw_idt.c                    |   7 --
 drivers/ntb/test/ntb_perf.c                        |   3 -
 drivers/scsi/bfa/bfa.h                             |   3 +-
 drivers/scsi/bfa/bfa_hw_cb.c                       |   2 -
 drivers/scsi/bfa/bfa_hw_ct.c                       |   2 -
 drivers/scsi/bnx2fc/bnx2fc_hwi.c                   |   2 -
 drivers/scsi/bnx2i/bnx2i_hwi.c                     |   3 -
 drivers/scsi/megaraid/megaraid_sas_base.c          |   1 -
 drivers/scsi/megaraid/megaraid_sas_fusion.c        |   1 -
 drivers/scsi/mpt3sas/mpt3sas_base.c                |   1 -
 drivers/scsi/qedf/qedf_io.c                        |   1 -
 drivers/scsi/qedi/qedi_fw.c                        |   1 -
 drivers/scsi/qla1280.c                             |  15 ---
 drivers/ssb/pci.c                                  |   1 -
 drivers/ssb/pcmcia.c                               |   4 -
 drivers/staging/comedi/drivers/mite.c              |   3 -
 drivers/staging/comedi/drivers/ni_660x.c           |   2 -
 drivers/staging/comedi/drivers/ni_mio_common.c     |   1 -
 drivers/staging/comedi/drivers/ni_pcidio.c         |   2 -
 drivers/staging/comedi/drivers/ni_tio.c            |   1 -
 drivers/staging/comedi/drivers/s626.c              |   2 -
 drivers/tty/serial/men_z135_uart.c                 |   1 -
 drivers/tty/serial/serial_txx9.c                   |   1 -
 drivers/usb/early/xhci-dbc.c                       |   4 -
 drivers/usb/host/xhci-dbgcap.c                     |   2 -
 include/asm-generic/io.h                           |   3 +-
 include/asm-generic/mmiowb.h                       |  60 ++++++++++++
 include/linux/qed/qed_if.h                         |   2 -
 include/linux/spinlock.h                           |  11 ++-
 kernel/Kconfig.locks                               |   3 +
 kernel/locking/spinlock.c                          |   5 +
 kernel/locking/spinlock_debug.c                    |   6 +-
 sound/soc/txx9/txx9aclc-ac97.c                     |   1 -
 178 files changed, 226 insertions(+), 764 deletions(-)
 create mode 100644 arch/ia64/include/asm/mmiowb.h
 create mode 100644 arch/mips/include/asm/mmiowb.h
 create mode 100644 arch/powerpc/include/asm/mmiowb.h
 create mode 100644 arch/riscv/include/asm/mmiowb.h
 create mode 100644 arch/sh/include/asm/mmiowb.h
 create mode 100644 include/asm-generic/mmiowb.h

-- 
2.11.0